drm/mediatek: Add missing IS_ERR check for ovl_adaptor platform devicegrafted

platform_device_register_data() can fail and return an ERR_PTR, but the
return value is used without checking, leading to an invalid pointer
being stored in ddp_comp[].dev and passed to component_match_add() and
mtk_ddp_comp_init(), which could result in a kernel crash.

Add an IS_ERR() check to jump to the error handling path on failure.

Fixes: 0d9eee9118b7 ("drm/mediatek: Add drm ovl_adaptor sub driver for MT8195")
Cc: stable@vger.kernel.org
Signed-off-by: Haojie Li <lihaojie@kylinos.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20260825100845.438893-1-lihaojie@kylinos.cn/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

1 files changed, 2182 insertions, 0 deletions

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
new file mode 100644
index 000000000..d7160f87a
--- /dev/null
+++ b/tools/perf/util/dwarf-aux.c
@@ -0,0 +1,2182 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * dwarf-aux.c : libdw auxiliary interfaces
+ */
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include "debug.h"
+#include "dwarf-aux.h"
+#include "dwarf-regs.h"
+#include "strbuf.h"
+#include "string2.h"
+
+/**
+ * cu_find_realpath - Find the realpath of the target file
+ * @cu_die: A DIE(dwarf information entry) of CU(compilation Unit)
+ * @fname:  The tail filename of the target file
+ *
+ * Find the real(long) path of @fname in @cu_die.
+ */
+const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname)
+{
+	Dwarf_Files *files;
+	size_t nfiles, i;
+	const char *src = NULL;
+	int ret;
+
+	if (!fname)
+		return NULL;
+
+	ret = dwarf_getsrcfiles(cu_die, &files, &nfiles);
+	if (ret != 0)
+		return NULL;
+
+	for (i = 0; i < nfiles; i++) {
+		src = dwarf_filesrc(files, i, NULL, NULL);
+		if (strtailcmp(src, fname) == 0)
+			break;
+	}
+	if (i == nfiles)
+		return NULL;
+	return src;
+}
+
+/**
+ * cu_get_comp_dir - Get the path of compilation directory
+ * @cu_die: a CU DIE
+ *
+ * Get the path of compilation directory of given @cu_die.
+ * Since this depends on DW_AT_comp_dir, older gcc will not
+ * embedded it. In that case, this returns NULL.
+ */
+const char *cu_get_comp_dir(Dwarf_Die *cu_die)
+{
+	Dwarf_Attribute attr;
+	if (dwarf_attr(cu_die, DW_AT_comp_dir, &attr) == NULL)
+		return NULL;
+	return dwarf_formstring(&attr);
+}
+
+/* Unlike dwarf_getsrc_die(), cu_getsrc_die() only returns statement line */
+static Dwarf_Line *cu_getsrc_die(Dwarf_Die *cu_die, Dwarf_Addr addr)
+{
+	Dwarf_Addr laddr;
+	Dwarf_Lines *lines;
+	Dwarf_Line *line;
+	size_t nlines, l, u, n;
+	bool flag;
+
+	if (dwarf_getsrclines(cu_die, &lines, &nlines) != 0 ||
+	    nlines == 0)
+		return NULL;
+
+	/* Lines are sorted by address, use binary search */
+	l = 0; u = nlines - 1;
+	while (l < u) {
+		n = u - (u - l) / 2;
+		line = dwarf_onesrcline(lines, n);
+		if (!line || dwarf_lineaddr(line, &laddr) != 0)
+			return NULL;
+		if (addr < laddr)
+			u = n - 1;
+		else
+			l = n;
+	}
+	/* Going backward to find the lowest line */
+	do {
+		line = dwarf_onesrcline(lines, --l);
+		if (!line || dwarf_lineaddr(line, &laddr) != 0)
+			return NULL;
+	} while (laddr == addr);
+	l++;
+	/* Going forward to find the statement line */
+	do {
+		line = dwarf_onesrcline(lines, l++);
+		if (!line || dwarf_lineaddr(line, &laddr) != 0 ||
+		    dwarf_linebeginstatement(line, &flag) != 0)
+			return NULL;
+		if (laddr > addr)
+			return NULL;
+	} while (!flag);
+
+	return line;
+}
+
+/**
+ * cu_find_lineinfo - Get a line number and file name for given address
+ * @cu_die: a CU DIE
+ * @addr: An address
+ * @fname: a pointer which returns the file name string
+ * @lineno: a pointer which returns the line number
+ *
+ * Find a line number and file name for @addr in @cu_die.
+ */
+int cu_find_lineinfo(Dwarf_Die *cu_die, Dwarf_Addr addr,
+		     const char **fname, int *lineno)
+{
+	Dwarf_Line *line;
+	Dwarf_Die die_mem;
+	Dwarf_Addr faddr;
+
+	if (die_find_realfunc(cu_die, addr, &die_mem)
+	    && die_entrypc(&die_mem, &faddr) == 0 &&
+	    faddr == addr) {
+		*fname = die_get_decl_file(&die_mem);
+		if (dwarf_decl_line(&die_mem, lineno) != 0)
+			return -ENOENT;
+		goto out;
+	}
+
+	line = cu_getsrc_die(cu_die, addr);
+	if (line && dwarf_lineno(line, lineno) == 0) {
+		*fname = dwarf_linesrc(line, NULL, NULL);
+		if (!*fname)
+			/* line number is useless without filename */
+			*lineno = 0;
+	}
+
+out:
+	return (*lineno && *fname) ? *lineno : -ENOENT;
+}
+
+static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data);
+
+/**
+ * cu_walk_functions_at - Walk on function DIEs at given address
+ * @cu_die: A CU DIE
+ * @addr: An address
+ * @callback: A callback which called with found DIEs
+ * @data: A user data
+ *
+ * Walk on function DIEs at given @addr in @cu_die. Passed DIEs
+ * should be subprogram or inlined-subroutines.
+ */
+int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
+		    int (*callback)(Dwarf_Die *, void *), void *data)
+{
+	Dwarf_Die die_mem;
+	Dwarf_Die *sc_die;
+	int ret = -ENOENT;
+
+	/* Inlined function could be recursive. Trace it until fail */
+	for (sc_die = die_find_realfunc(cu_die, addr, &die_mem);
+	     sc_die != NULL;
+	     sc_die = die_find_child(sc_die, __die_find_inline_cb, &addr,
+				     &die_mem)) {
+		ret = callback(sc_die, data);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/**
+ * die_get_linkage_name - Get the linkage name of the object
+ * @dw_die: A DIE of the object
+ *
+ * Get the linkage name attribute of given @dw_die.
+ * For C++ binary, the linkage name will be the mangled symbol.
+ */
+const char *die_get_linkage_name(Dwarf_Die *dw_die)
+{
+	Dwarf_Attribute attr;
+
+	if (dwarf_attr_integrate(dw_die, DW_AT_linkage_name, &attr) == NULL)
+		return NULL;
+	return dwarf_formstring(&attr);
+}
+
+/**
+ * die_compare_name - Compare diename and tname
+ * @dw_die: a DIE
+ * @tname: a string of target name
+ *
+ * Compare the name of @dw_die and @tname. Return false if @dw_die has no name.
+ */
+bool die_compare_name(Dwarf_Die *dw_die, const char *tname)
+{
+	const char *name;
+
+	name = dwarf_diename(dw_die);
+	return name ? (strcmp(tname, name) == 0) : false;
+}
+
+/**
+ * die_match_name - Match diename/linkage name and glob
+ * @dw_die: a DIE
+ * @glob: a string of target glob pattern
+ *
+ * Glob matching the name of @dw_die and @glob. Return false if matching fail.
+ * This also match linkage name.
+ */
+bool die_match_name(Dwarf_Die *dw_die, const char *glob)
+{
+	const char *name;
+
+	name = dwarf_diename(dw_die);
+	if (name && strglobmatch(name, glob))
+		return true;
+	/* fall back to check linkage name */
+	name = die_get_linkage_name(dw_die);
+	if (name && strglobmatch(name, glob))
+		return true;
+
+	return false;
+}
+
+/**
+ * die_get_call_lineno - Get callsite line number of inline-function instance
+ * @in_die: a DIE of an inlined function instance
+ *
+ * Get call-site line number of @in_die. This means from where the inline
+ * function is called.
+ */
+int die_get_call_lineno(Dwarf_Die *in_die)
+{
+	Dwarf_Attribute attr;
+	Dwarf_Word ret;
+
+	if (!dwarf_attr(in_die, DW_AT_call_line, &attr))
+		return -ENOENT;
+
+	dwarf_formudata(&attr, &ret);
+	return (int)ret;
+}
+
+/**
+ * die_get_type - Get type DIE
+ * @vr_die: a DIE of a variable
+ * @die_mem: where to store a type DIE
+ *
+ * Get a DIE of the type of given variable (@vr_die), and store
+ * it to die_mem. Return NULL if fails to get a type DIE.
+ */
+Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+{
+	Dwarf_Attribute attr;
+
+	if (dwarf_attr_integrate(vr_die, DW_AT_type, &attr) &&
+	    dwarf_formref_die(&attr, die_mem))
+		return die_mem;
+	else
+		return NULL;
+}
+
+/* Get a type die, but skip qualifiers */
+Dwarf_Die *__die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+{
+	int tag;
+
+	do {
+		vr_die = die_get_type(vr_die, die_mem);
+		if (!vr_die)
+			break;
+		tag = dwarf_tag(vr_die);
+	} while (tag == DW_TAG_const_type ||
+		 tag == DW_TAG_restrict_type ||
+		 tag == DW_TAG_volatile_type ||
+		 tag == DW_TAG_shared_type);
+
+	return vr_die;
+}
+
+/**
+ * die_get_real_type - Get a type die, but skip qualifiers and typedef
+ * @vr_die: a DIE of a variable
+ * @die_mem: where to store a type DIE
+ *
+ * Get a DIE of the type of given variable (@vr_die), and store
+ * it to die_mem. Return NULL if fails to get a type DIE.
+ * If the type is qualifiers (e.g. const) or typedef, this skips it
+ * and tries to find real type (structure or basic types, e.g. int).
+ */
+Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+{
+	do {
+		vr_die = __die_get_real_type(vr_die, die_mem);
+	} while (vr_die && dwarf_tag(vr_die) == DW_TAG_typedef);
+
+	return vr_die;
+}
+
+/**
+ * die_get_pointer_type - Get a pointer/array type die
+ * @type_die: a DIE of a type
+ * @die_mem: where to store a type DIE
+ *
+ * Get a pointer/array type DIE from @type_die. If the type is a typedef or
+ * qualifier (const, volatile, etc.), follow the chain to find the underlying
+ * pointer type.
+ */
+Dwarf_Die *die_get_pointer_type(Dwarf_Die *type_die, Dwarf_Die *die_mem)
+{
+	int tag;
+
+	do {
+		tag = dwarf_tag(type_die);
+		if (tag == DW_TAG_pointer_type || tag == DW_TAG_array_type)
+			return type_die;
+		if (tag != DW_TAG_typedef && tag != DW_TAG_const_type &&
+		    tag != DW_TAG_restrict_type && tag != DW_TAG_volatile_type &&
+		    tag != DW_TAG_shared_type)
+			return NULL;
+		type_die = die_get_type(type_die, die_mem);
+	} while (type_die);
+
+	return NULL;
+}
+
+/* Get attribute and translate it as a udata */
+static int die_get_attr_udata(Dwarf_Die *tp_die, unsigned int attr_name,
+			      Dwarf_Word *result)
+{
+	Dwarf_Attribute attr;
+
+	if (dwarf_attr_integrate(tp_die, attr_name, &attr) == NULL ||
+	    dwarf_formudata(&attr, result) != 0)
+		return -ENOENT;
+
+	return 0;
+}
+
+/**
+ * die_is_signed_type - Check whether a type DIE is signed or not
+ * @tp_die: a DIE of a type
+ *
+ * Get the encoding of @tp_die and return true if the encoding
+ * is signed.
+ */
+bool die_is_signed_type(Dwarf_Die *tp_die)
+{
+	Dwarf_Word ret;
+
+	if (die_get_attr_udata(tp_die, DW_AT_encoding, &ret))
+		return false;
+
+	return (ret == DW_ATE_signed_char || ret == DW_ATE_signed ||
+		ret == DW_ATE_signed_fixed);
+}
+
+/**
+ * die_is_func_def - Ensure that this DIE is a subprogram and definition
+ * @dw_die: a DIE
+ *
+ * Ensure that this DIE is a subprogram and NOT a declaration. This
+ * returns true if @dw_die is a function definition.
+ **/
+bool die_is_func_def(Dwarf_Die *dw_die)
+{
+	Dwarf_Attribute attr;
+	Dwarf_Addr addr = 0;
+
+	if (dwarf_tag(dw_die) != DW_TAG_subprogram)
+		return false;
+
+	if (dwarf_attr(dw_die, DW_AT_declaration, &attr))
+		return false;
+
+	/*
+	 * DW_AT_declaration can be lost from function declaration
+	 * by gcc's bug #97060.
+	 * So we need to check this subprogram DIE has DW_AT_inline
+	 * or an entry address.
+	 */
+	if (!dwarf_attr(dw_die, DW_AT_inline, &attr) &&
+	    die_entrypc(dw_die, &addr) < 0)
+		return false;
+
+	return true;
+}
+
+/**
+ * die_entrypc - Returns entry PC (the lowest address) of a DIE
+ * @dw_die: a DIE
+ * @addr: where to store entry PC
+ *
+ * Since dwarf_entrypc() does not return entry PC if the DIE has only address
+ * range, we have to use this to retrieve the lowest address from the address
+ * range attribute.
+ */
+int die_entrypc(Dwarf_Die *dw_die, Dwarf_Addr *addr)
+{
+	Dwarf_Addr base, end;
+	Dwarf_Attribute attr;
+
+	if (!addr)
+		return -EINVAL;
+
+	if (dwarf_entrypc(dw_die, addr) == 0)
+		return 0;
+
+	/*
+	 *  Since the dwarf_ranges() will return 0 if there is no
+	 * DW_AT_ranges attribute, we should check it first.
+	 */
+	if (!dwarf_attr(dw_die, DW_AT_ranges, &attr))
+		return -ENOENT;
+
+	return dwarf_ranges(dw_die, 0, &base, addr, &end) < 0 ? -ENOENT : 0;
+}
+
+/**
+ * die_is_func_instance - Ensure that this DIE is an instance of a subprogram
+ * @dw_die: a DIE
+ *
+ * Ensure that this DIE is an instance (which has an entry address).
+ * This returns true if @dw_die is a function instance. If not, the @dw_die
+ * must be a prototype. You can use die_walk_instances() to find actual
+ * instances.
+ **/
+bool die_is_func_instance(Dwarf_Die *dw_die)
+{
+	Dwarf_Addr tmp;
+	Dwarf_Attribute attr_mem;
+	int tag = dwarf_tag(dw_die);
+
+	if (tag != DW_TAG_subprogram &&
+	    tag != DW_TAG_inlined_subroutine)
+		return false;
+
+	return dwarf_entrypc(dw_die, &tmp) == 0 ||
+		dwarf_attr(dw_die, DW_AT_ranges, &attr_mem) != NULL;
+}
+
+/**
+ * die_get_data_member_location - Get the data-member offset
+ * @mb_die: a DIE of a member of a data structure
+ * @offs: The offset of the member in the data structure
+ *
+ * Get the offset of @mb_die in the data structure including @mb_die, and
+ * stores result offset to @offs. If any error occurs this returns errno.
+ */
+int die_get_data_member_location(Dwarf_Die *mb_die, Dwarf_Word *offs)
+{
+	Dwarf_Attribute attr;
+	Dwarf_Op *expr;
+	size_t nexpr;
+	int ret;
+
+	if (dwarf_attr_integrate(mb_die, DW_AT_data_member_location, &attr) == NULL)
+		return -ENOENT;
+
+	if (dwarf_formudata(&attr, offs) != 0) {
+		/* DW_AT_data_member_location should be DW_OP_plus_uconst */
+		ret = dwarf_getlocation(&attr, &expr, &nexpr);
+		if (ret < 0 || nexpr == 0)
+			return -ENOENT;
+
+		if (expr[0].atom != DW_OP_plus_uconst || nexpr != 1) {
+			pr_debug("Unable to get offset:Unexpected OP %x (%zd)\n",
+				 expr[0].atom, nexpr);
+			return -ENOTSUP;
+		}
+		*offs = (Dwarf_Word)expr[0].number;
+	}
+	return 0;
+}
+
+/* Get the call file index number in CU DIE */
+static int die_get_call_fileno(Dwarf_Die *in_die)
+{
+	Dwarf_Word idx;
+
+	if (die_get_attr_udata(in_die, DW_AT_call_file, &idx) == 0)
+		return (int)idx;
+	else
+		return -ENOENT;
+}
+
+/* Get the declared file index number in CU DIE */
+static int die_get_decl_fileno(Dwarf_Die *pdie)
+{
+	Dwarf_Word idx;
+
+	if (die_get_attr_udata(pdie, DW_AT_decl_file, &idx) == 0)
+		return (int)idx;
+	else
+		return -ENOENT;
+}
+
+/* Return the file name by index */
+static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
+{
+	Dwarf_Die cu_die;
+	Dwarf_Files *files;
+	Dwarf_Attribute attr_mem;
+
+	if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
+	    !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
+	    dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
+		return NULL;
+
+	return dwarf_filesrc(files, idx, NULL, NULL);
+}
+
+/**
+ * die_get_call_file - Get callsite file name of inlined function instance
+ * @in_die: a DIE of an inlined function instance
+ *
+ * Get call-site file name of @in_die. This means from which file the inline
+ * function is called.
+ */
+const char *die_get_call_file(Dwarf_Die *in_die)
+{
+	return die_get_file_name(in_die, die_get_call_fileno(in_die));
+}
+
+/**
+ * die_get_decl_file - Find the declared file name of this DIE
+ * @dw_die: a DIE for something declared.
+ *
+ * Get declared file name of @dw_die.
+ * NOTE: Since some version of clang DWARF5 implementation incorrectly uses
+ * file index 0 for DW_AT_decl_file, die_get_decl_file() will return NULL for
+ * such cases. Use this function instead.
+ */
+const char *die_get_decl_file(Dwarf_Die *dw_die)
+{
+	return die_get_file_name(dw_die, die_get_decl_fileno(dw_die));
+}
+
+/**
+ * die_find_child - Generic DIE search function in DIE tree
+ * @rt_die: a root DIE
+ * @callback: a callback function
+ * @data: a user data passed to the callback function
+ * @die_mem: a buffer for result DIE
+ *
+ * Trace DIE tree from @rt_die and call @callback for each child DIE.
+ * If @callback returns DIE_FIND_CB_END, this stores the DIE into
+ * @die_mem and returns it. If @callback returns DIE_FIND_CB_CONTINUE,
+ * this continues to trace the tree. Optionally, @callback can return
+ * DIE_FIND_CB_CHILD and DIE_FIND_CB_SIBLING, those means trace only
+ * the children and trace only the siblings respectively.
+ * Returns NULL if @callback can't find any appropriate DIE.
+ */
+Dwarf_Die *die_find_child(Dwarf_Die *rt_die,
+			  int (*callback)(Dwarf_Die *, void *),
+			  void *data, Dwarf_Die *die_mem)
+{
+	Dwarf_Die child_die;
+	int ret;
+
+	ret = dwarf_child(rt_die, die_mem);
+	if (ret != 0)
+		return NULL;
+
+	do {
+		ret = callback(die_mem, data);
+		if (ret == DIE_FIND_CB_END)
+			return die_mem;
+
+		if ((ret & DIE_FIND_CB_CHILD) &&
+		    die_find_child(die_mem, callback, data, &child_die)) {
+			memcpy(die_mem, &child_die, sizeof(Dwarf_Die));
+			return die_mem;
+		}
+	} while ((ret & DIE_FIND_CB_SIBLING) &&
+		 dwarf_siblingof(die_mem, die_mem) == 0);
+
+	return NULL;
+}
+
+struct __addr_die_search_param {
+	Dwarf_Addr	addr;
+	Dwarf_Die	*die_mem;
+};
+
+static int __die_search_func_tail_cb(Dwarf_Die *fn_die, void *data)
+{
+	struct __addr_die_search_param *ad = data;
+	Dwarf_Addr addr = 0;
+
+	if (dwarf_tag(fn_die) == DW_TAG_subprogram &&
+	    !dwarf_highpc(fn_die, &addr) &&
+	    addr == ad->addr) {
+		memcpy(ad->die_mem, fn_die, sizeof(Dwarf_Die));
+		return DWARF_CB_ABORT;
+	}
+	return DWARF_CB_OK;
+}
+
+/**
+ * die_find_tailfunc - Search for a non-inlined function with tail call at
+ * given address
+ * @cu_die: a CU DIE which including @addr
+ * @addr: target address
+ * @die_mem: a buffer for result DIE
+ *
+ * Search for a non-inlined function DIE with tail call at @addr. Stores the
+ * DIE to @die_mem and returns it if found. Returns NULL if failed.
+ */
+Dwarf_Die *die_find_tailfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
+				    Dwarf_Die *die_mem)
+{
+	struct __addr_die_search_param ad;
+	ad.addr = addr;
+	ad.die_mem = die_mem;
+	/* dwarf_getscopes can't find subprogram. */
+	if (dwarf_getfuncs(cu_die, __die_search_func_tail_cb, &ad, 0) <= 0)
+		return NULL;
+	else
+		return die_mem;
+}
+
+/* die_find callback for non-inlined function search */
+static int __die_search_func_cb(Dwarf_Die *fn_die, void *data)
+{
+	struct __addr_die_search_param *ad = data;
+
+	/*
+	 * Since a declaration entry doesn't has given pc, this always returns
+	 * function definition entry.
+	 */
+	if (dwarf_tag(fn_die) == DW_TAG_subprogram &&
+	    dwarf_haspc(fn_die, ad->addr)) {
+		memcpy(ad->die_mem, fn_die, sizeof(Dwarf_Die));
+		return DWARF_CB_ABORT;
+	}
+	return DWARF_CB_OK;
+}
+
+/**
+ * die_find_realfunc - Search a non-inlined function at given address
+ * @cu_die: a CU DIE which including @addr
+ * @addr: target address
+ * @die_mem: a buffer for result DIE
+ *
+ * Search a non-inlined function DIE which includes @addr. Stores the
+ * DIE to @die_mem and returns it if found. Returns NULL if failed.
+ */
+Dwarf_Die *die_find_realfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
+				    Dwarf_Die *die_mem)
+{
+	struct __addr_die_search_param ad;
+	ad.addr = addr;
+	ad.die_mem = die_mem;
+	/* dwarf_getscopes can't find subprogram. */
+	if (dwarf_getfuncs(cu_die, __die_search_func_cb, &ad, 0) <= 0)
+		return NULL;
+	else
+		return die_mem;
+}
+
+/* die_find callback for inline function search */
+static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data)
+{
+	Dwarf_Addr *addr = data;
+
+	if (dwarf_tag(die_mem) == DW_TAG_inlined_subroutine &&
+	    dwarf_haspc(die_mem, *addr))
+		return DIE_FIND_CB_END;
+
+	return DIE_FIND_CB_CONTINUE;
+}
+
+/**
+ * die_find_top_inlinefunc - Search the top inlined function at given address
+ * @sp_die: a subprogram DIE which including @addr
+ * @addr: target address
+ * @die_mem: a buffer for result DIE
+ *
+ * Search an inlined function DIE which includes @addr. Stores the
+ * DIE to @die_mem and returns it if found. Returns NULL if failed.
+ * Even if several inlined functions are expanded recursively, this
+ * doesn't trace it down, and returns the topmost one.
+ */
+Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
+				   Dwarf_Die *die_mem)
+{
+	return die_find_child(sp_die, __die_find_inline_cb, &addr, die_mem);
+}
+
+/**
+ * die_find_inlinefunc - Search an inlined function at given address
+ * @sp_die: a subprogram DIE which including @addr
+ * @addr: target address
+ * @die_mem: a buffer for result DIE
+ *
+ * Search an inlined function DIE which includes @addr. Stores the
+ * DIE to @die_mem and returns it if found. Returns NULL if failed.
+ * If several inlined functions are expanded recursively, this trace
+ * it down and returns deepest one.
+ */
+Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
+			       Dwarf_Die *die_mem)
+{
+	Dwarf_Die tmp_die;
+
+	sp_die = die_find_child(sp_die, __die_find_inline_cb, &addr, &tmp_die);
+	if (!sp_die)
+		return NULL;
+
+	/* Inlined function could be recursive. Trace it until fail */
+	while (sp_die) {
+		memcpy(die_mem, sp_die, sizeof(Dwarf_Die));
+		sp_die = die_find_child(sp_die, __die_find_inline_cb, &addr,
+					&tmp_die);
+	}
+
+	return die_mem;
+}
+
+static int __die_find_func_rettype_cb(Dwarf_Die *die_mem, void *data)
+{
+	const char *func_name;
+
+	if (dwarf_tag(die_mem) != DW_TAG_subprogram)
+		return DIE_FIND_CB_SIBLING;
+
+	func_name = dwarf_diename(die_mem);
+	if (func_name && !strcmp(func_name, data))
+		return DIE_FIND_CB_END;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_find_func_rettype - Search a return type of function
+ * @cu_die: a CU DIE
+ * @name: target function name
+ * @die_mem: a buffer for result DIE
+ *
+ * Search a non-inlined function which matches to @name and stores the
+ * return type of the function to @die_mem and returns it if found.
+ * Returns NULL if failed.  Note that it doesn't needs to find a
+ * definition of the function, so it doesn't match with address.
+ * Most likely, it can find a declaration at the top level.  Thus the
+ * callback function continues to sibling entries only.
+ */
+Dwarf_Die *die_find_func_rettype(Dwarf_Die *cu_die, const char *name,
+				 Dwarf_Die *die_mem)
+{
+	Dwarf_Die tmp_die;
+
+	cu_die = die_find_child(cu_die, __die_find_func_rettype_cb,
+				(void *)name, &tmp_die);
+	if (!cu_die)
+		return NULL;
+
+	if (die_get_real_type(&tmp_die, die_mem) == NULL)
+		return NULL;
+
+	return die_mem;
+}
+
+struct __instance_walk_param {
+	void    *addr;
+	int	(*callback)(Dwarf_Die *, void *);
+	void    *data;
+	int	retval;
+};
+
+static int __die_walk_instances_cb(Dwarf_Die *inst, void *data)
+{
+	struct __instance_walk_param *iwp = data;
+	Dwarf_Attribute attr_mem;
+	Dwarf_Die origin_mem;
+	Dwarf_Attribute *attr;
+	Dwarf_Die *origin;
+	int tmp;
+
+	if (!die_is_func_instance(inst))
+		return DIE_FIND_CB_CONTINUE;
+
+	attr = dwarf_attr(inst, DW_AT_abstract_origin, &attr_mem);
+	if (attr == NULL)
+		return DIE_FIND_CB_CONTINUE;
+
+	origin = dwarf_formref_die(attr, &origin_mem);
+	if (origin == NULL || origin->addr != iwp->addr)
+		return DIE_FIND_CB_CONTINUE;
+
+	/* Ignore redundant instances */
+	if (dwarf_tag(inst) == DW_TAG_inlined_subroutine) {
+		if (dwarf_decl_line(origin, &tmp) == 0 && die_get_call_lineno(inst) == tmp) {
+			tmp = die_get_decl_fileno(origin);
+			if (die_get_call_fileno(inst) == tmp)
+				return DIE_FIND_CB_CONTINUE;
+		}
+	}
+
+	iwp->retval = iwp->callback(inst, iwp->data);
+
+	return (iwp->retval) ? DIE_FIND_CB_END : DIE_FIND_CB_CONTINUE;
+}
+
+/**
+ * die_walk_instances - Walk on instances of given DIE
+ * @or_die: an abstract original DIE
+ * @callback: a callback function which is called with instance DIE
+ * @data: user data
+ *
+ * Walk on the instances of give @in_die. @in_die must be an inlined function
+ * declaration. This returns the return value of @callback if it returns
+ * non-zero value, or -ENOENT if there is no instance.
+ */
+int die_walk_instances(Dwarf_Die *or_die, int (*callback)(Dwarf_Die *, void *),
+		       void *data)
+{
+	Dwarf_Die cu_die;
+	Dwarf_Die die_mem;
+	struct __instance_walk_param iwp = {
+		.addr = or_die->addr,
+		.callback = callback,
+		.data = data,
+		.retval = -ENOENT,
+	};
+
+	if (dwarf_diecu(or_die, &cu_die, NULL, NULL) == NULL)
+		return -ENOENT;
+
+	die_find_child(&cu_die, __die_walk_instances_cb, &iwp, &die_mem);
+
+	return iwp.retval;
+}
+
+/* Line walker internal parameters */
+struct __line_walk_param {
+	bool recursive;
+	line_walk_callback_t callback;
+	void *data;
+	int retval;
+};
+
+static int __die_walk_funclines_cb(Dwarf_Die *in_die, void *data)
+{
+	struct __line_walk_param *lw = data;
+	Dwarf_Addr addr = 0;
+	const char *fname;
+	int lineno;
+
+	if (dwarf_tag(in_die) == DW_TAG_inlined_subroutine) {
+		fname = die_get_call_file(in_die);
+		lineno = die_get_call_lineno(in_die);
+		if (fname && lineno > 0 && die_entrypc(in_die, &addr) == 0) {
+			lw->retval = lw->callback(fname, lineno, addr, lw->data);
+			if (lw->retval != 0)
+				return DIE_FIND_CB_END;
+		}
+		if (!lw->recursive)
+			return DIE_FIND_CB_SIBLING;
+	}
+
+	if (addr) {
+		fname = die_get_decl_file(in_die);
+		if (fname && dwarf_decl_line(in_die, &lineno) == 0) {
+			lw->retval = lw->callback(fname, lineno, addr, lw->data);
+			if (lw->retval != 0)
+				return DIE_FIND_CB_END;
+		}
+	}
+
+	/* Continue to search nested inlined function call-sites */
+	return DIE_FIND_CB_CONTINUE;
+}
+
+/* Walk on lines of blocks included in given DIE */
+static int __die_walk_funclines(Dwarf_Die *sp_die, bool recursive,
+				line_walk_callback_t callback, void *data)
+{
+	struct __line_walk_param lw = {
+		.recursive = recursive,
+		.callback = callback,
+		.data = data,
+		.retval = 0,
+	};
+	Dwarf_Die die_mem;
+	Dwarf_Addr addr;
+	const char *fname;
+	int lineno;
+
+	/* Handle function declaration line */
+	fname = die_get_decl_file(sp_die);
+	if (fname && dwarf_decl_line(sp_die, &lineno) == 0 &&
+	    die_entrypc(sp_die, &addr) == 0) {
+		lw.retval = callback(fname, lineno, addr, data);
+		if (lw.retval != 0)
+			goto done;
+	}
+	die_find_child(sp_die, __die_walk_funclines_cb, &lw, &die_mem);
+done:
+	return lw.retval;
+}
+
+static int __die_walk_culines_cb(Dwarf_Die *sp_die, void *data)
+{
+	struct __line_walk_param *lw = data;
+
+	/*
+	 * Since inlined function can include another inlined function in
+	 * the same file, we need to walk in it recursively.
+	 */
+	lw->retval = __die_walk_funclines(sp_die, true, lw->callback, lw->data);
+	if (lw->retval != 0)
+		return DWARF_CB_ABORT;
+
+	return DWARF_CB_OK;
+}
+
+/**
+ * die_walk_lines - Walk on lines inside given DIE
+ * @rt_die: a root DIE (CU, subprogram or inlined_subroutine)
+ * @callback: callback routine
+ * @data: user data
+ *
+ * Walk on all lines inside given @rt_die and call @callback on each line.
+ * If the @rt_die is a function, walk only on the lines inside the function,
+ * otherwise @rt_die must be a CU DIE.
+ * Note that this walks not only dwarf line list, but also function entries
+ * and inline call-site.
+ */
+int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
+{
+	Dwarf_Lines *lines;
+	Dwarf_Line *line;
+	Dwarf_Addr addr;
+	const char *fname, *decf = NULL, *inf = NULL;
+	int lineno, ret = 0;
+	int decl = 0, inl;
+	Dwarf_Die die_mem, *cu_die;
+	size_t nlines, i;
+	bool flag;
+
+	/* Get the CU die */
+	if (dwarf_tag(rt_die) != DW_TAG_compile_unit) {
+		cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
+		dwarf_decl_line(rt_die, &decl);
+		decf = die_get_decl_file(rt_die);
+	} else
+		cu_die = rt_die;
+	if (!cu_die) {
+		pr_debug2("Failed to get CU from given DIE.\n");
+		return -EINVAL;
+	}
+
+	/* Get lines list in the CU */
+	if (dwarf_getsrclines(cu_die, &lines, &nlines) != 0) {
+		pr_debug2("Failed to get source lines on this CU.\n");
+		return -ENOENT;
+	}
+	pr_debug2("Get %zd lines from this CU\n", nlines);
+
+	/* Walk on the lines on lines list */
+	for (i = 0; i < nlines; i++) {
+		line = dwarf_onesrcline(lines, i);
+		if (line == NULL ||
+		    dwarf_lineno(line, &lineno) != 0 ||
+		    dwarf_lineaddr(line, &addr) != 0) {
+			pr_debug2("Failed to get line info. "
+				  "Possible error in debuginfo.\n");
+			continue;
+		}
+		/* Skip end-of-sequence */
+		if (dwarf_lineendsequence(line, &flag) != 0 || flag)
+			continue;
+		/* Skip Non statement line-info */
+		if (dwarf_linebeginstatement(line, &flag) != 0 || !flag)
+			continue;
+		/* Filter lines based on address */
+		if (rt_die != cu_die) {
+			/*
+			 * Address filtering
+			 * The line is included in given function, and
+			 * no inline block includes it.
+			 */
+			if (!dwarf_haspc(rt_die, addr))
+				continue;
+
+			if (die_find_inlinefunc(rt_die, addr, &die_mem)) {
+				/* Call-site check */
+				inf = die_get_call_file(&die_mem);
+				if ((inf == decf || (inf && decf && !strcmp(inf, decf))) &&
+				    die_get_call_lineno(&die_mem) == lineno)
+					goto found;
+
+				if (dwarf_decl_line(&die_mem, &inl) != 0)
+					inl = 0;
+				if (inl != decl ||
+				    decf != die_get_decl_file(&die_mem))
+					continue;
+			}
+		}
+found:
+		/* Get source line */
+		fname = dwarf_linesrc(line, NULL, NULL);
+
+		ret = callback(fname, lineno, addr, data);
+		if (ret != 0)
+			return ret;
+	}
+
+	/*
+	 * Dwarf lines doesn't include function declarations and inlined
+	 * subroutines. We have to check functions list or given function.
+	 */
+	if (rt_die != cu_die)
+		/*
+		 * Don't need walk inlined functions recursively, because
+		 * inner inlined functions don't have the lines of the
+		 * specified function.
+		 */
+		ret = __die_walk_funclines(rt_die, false, callback, data);
+	else {
+		struct __line_walk_param param = {
+			.callback = callback,
+			.data = data,
+			.retval = 0,
+		};
+		if (dwarf_getfuncs(cu_die, __die_walk_culines_cb, &param, 0) < 0)
+			ret = -EINVAL;
+		else
+			ret = param.retval;
+	}
+
+	return ret;
+}
+
+struct __find_variable_param {
+	const char *name;
+	Dwarf_Addr addr;
+};
+
+static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data)
+{
+	struct __find_variable_param *fvp = data;
+	Dwarf_Attribute attr;
+	int tag;
+
+	tag = dwarf_tag(die_mem);
+	if ((tag == DW_TAG_formal_parameter ||
+	     tag == DW_TAG_variable) &&
+	    die_compare_name(die_mem, fvp->name) &&
+	/*
+	 * Does the DIE have location information or const value
+	 * or external instance?
+	 */
+	    (dwarf_attr(die_mem, DW_AT_external, &attr) ||
+	     dwarf_attr(die_mem, DW_AT_location, &attr) ||
+	     dwarf_attr(die_mem, DW_AT_const_value, &attr)))
+		return DIE_FIND_CB_END;
+	if (dwarf_haspc(die_mem, fvp->addr))
+		return DIE_FIND_CB_CONTINUE;
+	else
+		return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_find_variable_at - Find a given name variable at given address
+ * @sp_die: a function DIE
+ * @name: variable name
+ * @addr: address
+ * @die_mem: a buffer for result DIE
+ *
+ * Find a variable DIE called @name at @addr in @sp_die.
+ */
+Dwarf_Die *die_find_variable_at(Dwarf_Die *sp_die, const char *name,
+				Dwarf_Addr addr, Dwarf_Die *die_mem)
+{
+	struct __find_variable_param fvp = { .name = name, .addr = addr};
+
+	return die_find_child(sp_die, __die_find_variable_cb, (void *)&fvp,
+			      die_mem);
+}
+
+static int __die_find_member_cb(Dwarf_Die *die_mem, void *data)
+{
+	const char *name = data;
+
+	if (dwarf_tag(die_mem) == DW_TAG_member) {
+		if (die_compare_name(die_mem, name))
+			return DIE_FIND_CB_END;
+		else if (!dwarf_diename(die_mem)) {	/* Unnamed structure */
+			Dwarf_Die type_die, tmp_die;
+			if (die_get_type(die_mem, &type_die) &&
+			    die_find_member(&type_die, name, &tmp_die))
+				return DIE_FIND_CB_END;
+		}
+	}
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_find_member - Find a given name member in a data structure
+ * @st_die: a data structure type DIE
+ * @name: member name
+ * @die_mem: a buffer for result DIE
+ *
+ * Find a member DIE called @name in @st_die.
+ */
+Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
+			   Dwarf_Die *die_mem)
+{
+	return die_find_child(st_die, __die_find_member_cb, (void *)name,
+			      die_mem);
+}
+
+/**
+ * die_get_typename_from_type - Get the name of given type DIE
+ * @type_die: a type DIE
+ * @buf: a strbuf for result type name
+ *
+ * Get the name of @type_die and stores it to @buf. Return 0 if succeeded.
+ * and Return -ENOENT if failed to find type name.
+ * Note that the result will stores typedef name if possible, and stores
+ * "*(function_type)" if the type is a function pointer.
+ */
+int die_get_typename_from_type(Dwarf_Die *type_die, struct strbuf *buf)
+{
+	int tag, ret;
+	const char *tmp = "";
+
+	tag = dwarf_tag(type_die);
+	if (tag == DW_TAG_pointer_type)
+		tmp = "*";
+	else if (tag == DW_TAG_array_type)
+		tmp = "[]";
+	else if (tag == DW_TAG_subroutine_type) {
+		/* Function pointer */
+		return strbuf_add(buf, "(function_type)", 15);
+	} else {
+		const char *name = dwarf_diename(type_die);
+
+		if (tag == DW_TAG_union_type)
+			tmp = "union ";
+		else if (tag == DW_TAG_structure_type)
+			tmp = "struct ";
+		else if (tag == DW_TAG_enumeration_type)
+			tmp = "enum ";
+		else if (name == NULL)
+			return -ENOENT;
+		/* Write a base name */
+		return strbuf_addf(buf, "%s%s", tmp, name ?: "");
+	}
+	ret = die_get_typename(type_die, buf);
+	if (ret < 0) {
+		/* void pointer has no type attribute */
+		if (tag == DW_TAG_pointer_type && ret == -ENOENT)
+			return strbuf_addf(buf, "void*");
+
+		return ret;
+	}
+	return strbuf_addstr(buf, tmp);
+}
+
+/**
+ * die_get_typename - Get the name of given variable DIE
+ * @vr_die: a variable DIE
+ * @buf: a strbuf for result type name
+ *
+ * Get the name of @vr_die and stores it to @buf. Return 0 if succeeded.
+ * and Return -ENOENT if failed to find type name.
+ * Note that the result will stores typedef name if possible, and stores
+ * "*(function_type)" if the type is a function pointer.
+ */
+int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf)
+{
+	Dwarf_Die type;
+
+	if (__die_get_real_type(vr_die, &type) == NULL)
+		return -ENOENT;
+
+	return die_get_typename_from_type(&type, buf);
+}
+
+/**
+ * die_get_varname - Get the name and type of given variable DIE
+ * @vr_die: a variable DIE
+ * @buf: a strbuf for type and variable name
+ *
+ * Get the name and type of @vr_die and stores it in @buf as "type\tname".
+ */
+int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf)
+{
+	int ret;
+
+	ret = die_get_typename(vr_die, buf);
+	if (ret < 0) {
+		pr_debug("Failed to get type, make it unknown.\n");
+		ret = strbuf_add(buf, "(unknown_type)", 14);
+	}
+
+	return ret < 0 ? ret : strbuf_addf(buf, "\t%s", dwarf_diename(vr_die));
+}
+
+static int reg_from_dwarf_op(Dwarf_Op *op)
+{
+	switch (op->atom) {
+	case DW_OP_reg0 ... DW_OP_reg31:
+		return op->atom - DW_OP_reg0;
+	case DW_OP_breg0 ... DW_OP_breg31:
+		return op->atom - DW_OP_breg0;
+	case DW_OP_regx:
+	case DW_OP_bregx:
+		return op->number;
+	case DW_OP_fbreg:
+		return DWARF_REG_FB;
+	default:
+		break;
+	}
+	return -1;
+}
+
+static int offset_from_dwarf_op(Dwarf_Op *op)
+{
+	switch (op->atom) {
+	case DW_OP_reg0 ... DW_OP_reg31:
+	case DW_OP_regx:
+		return 0;
+	case DW_OP_breg0 ... DW_OP_breg31:
+	case DW_OP_fbreg:
+		return op->number;
+	case DW_OP_bregx:
+		return op->number2;
+	default:
+		break;
+	}
+	return -1;
+}
+
+static bool check_allowed_ops(Dwarf_Op *ops, size_t nops)
+{
+	/* The first op is checked separately */
+	ops++;
+	nops--;
+
+	/*
+	 * It needs to make sure if the location expression matches to the given
+	 * register and offset exactly.  Thus it rejects any complex expressions
+	 * and only allows a few of selected operators that doesn't change the
+	 * location.
+	 */
+	while (nops) {
+		switch (ops->atom) {
+		case DW_OP_stack_value:
+		case DW_OP_deref_size:
+		case DW_OP_deref:
+		case DW_OP_piece:
+			break;
+		default:
+			return false;
+		}
+		ops++;
+		nops--;
+	}
+	return true;
+}
+
+/**
+ * die_get_var_innermost_scope - Get innermost scope range of given variable DIE
+ * @sp_die: a subprogram DIE
+ * @vr_die: a variable DIE
+ * @buf: a strbuf for variable byte offset range
+ *
+ * Get the innermost scope range of @vr_die and stores it in @buf as
+ * "@<function_name+[NN-NN,NN-NN]>".
+ */
+static int die_get_var_innermost_scope(Dwarf_Die *sp_die, Dwarf_Die *vr_die,
+				struct strbuf *buf)
+{
+	Dwarf_Die *scopes;
+	int count;
+	size_t offset = 0;
+	Dwarf_Addr base;
+	Dwarf_Addr start, end;
+	Dwarf_Addr entry;
+	int ret;
+	bool first = true;
+	const char *name;
+
+	ret = die_entrypc(sp_die, &entry);
+	if (ret)
+		return ret;
+
+	name = dwarf_diename(sp_die);
+	if (!name)
+		return -ENOENT;
+
+	count = dwarf_getscopes_die(vr_die, &scopes);
+
+	/* (*SCOPES)[1] is the DIE for the scope containing that scope */
+	if (count <= 1) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	while ((offset = dwarf_ranges(&scopes[1], offset, &base,
+					&start, &end)) > 0) {
+		start -= entry;
+		end -= entry;
+
+		if (first) {
+			ret = strbuf_addf(buf, "@<%s+[%" PRIu64 "-%" PRIu64,
+					  name, start, end);
+			first = false;
+		} else {
+			ret = strbuf_addf(buf, ",%" PRIu64 "-%" PRIu64,
+					  start, end);
+		}
+		if (ret < 0)
+			goto out;
+	}
+
+	if (!first)
+		ret = strbuf_add(buf, "]>", 2);
+
+out:
+	free(scopes);
+	return ret;
+}
+
+/**
+ * die_get_var_range - Get byte offset range of given variable DIE
+ * @sp_die: a subprogram DIE
+ * @vr_die: a variable DIE
+ * @buf: a strbuf for type and variable name and byte offset range
+ *
+ * Get the byte offset range of @vr_die and stores it in @buf as
+ * "@<function_name+[NN-NN,NN-NN]>".
+ */
+int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf)
+{
+	int ret = 0;
+	Dwarf_Addr base;
+	Dwarf_Addr start, end;
+	Dwarf_Addr entry;
+	Dwarf_Op *op;
+	size_t nops;
+	size_t offset = 0;
+	Dwarf_Attribute attr;
+	bool first = true;
+	const char *name;
+
+	ret = die_entrypc(sp_die, &entry);
+	if (ret)
+		return ret;
+
+	name = dwarf_diename(sp_die);
+	if (!name)
+		return -ENOENT;
+
+	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
+		return -EINVAL;
+
+	while ((offset = dwarf_getlocations(&attr, offset, &base,
+					&start, &end, &op, &nops)) > 0) {
+		if (start == 0) {
+			/* Single Location Descriptions */
+			ret = die_get_var_innermost_scope(sp_die, vr_die, buf);
+			goto out;
+		}
+
+		/* Location Lists */
+		start -= entry;
+		end -= entry;
+		if (first) {
+			ret = strbuf_addf(buf, "@<%s+[%" PRIu64 "-%" PRIu64,
+					  name, start, end);
+			first = false;
+		} else {
+			ret = strbuf_addf(buf, ",%" PRIu64 "-%" PRIu64,
+					  start, end);
+		}
+		if (ret < 0)
+			goto out;
+	}
+
+	if (!first)
+		ret = strbuf_add(buf, "]>", 2);
+out:
+	return ret;
+}
+
+/* Interval parameters for __die_find_var_reg_cb() */
+struct find_var_data {
+	/* Target instruction address */
+	Dwarf_Addr pc;
+	/* Target memory address (for global data) */
+	Dwarf_Addr addr;
+	/* Target register */
+	unsigned reg;
+	/* Access data type */
+	Dwarf_Die type;
+	/* Access offset, set for global data */
+	int offset;
+	/* True if the current register is the frame base */
+	bool is_fbreg;
+};
+
+/* Max number of registers DW_OP_regN supports */
+#define DWARF_OP_DIRECT_REGS  32
+
+static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
+			     s64 addr_offset, s64 addr_type, bool is_pointer)
+{
+	Dwarf_Word size;
+	Dwarf_Die ptr_die;
+	Dwarf_Die *ptr_type;
+	s64 offset = addr_offset - addr_type;
+
+	if (offset < 0)
+		return false;
+
+	if (__die_get_real_type(die_mem, &data->type) == NULL)
+		return false;
+
+	ptr_type = die_get_pointer_type(&data->type, &ptr_die);
+	if (is_pointer && ptr_type) {
+		/* Get the target type of the pointer */
+		if (__die_get_real_type(ptr_type, &data->type) == NULL)
+			return false;
+	}
+
+	if (offset == 0) {
+		/* Update offset relative to the start of the variable */
+		data->offset = 0;
+		return true;
+	}
+
+	if (dwarf_aggregate_size(&data->type, &size) < 0)
+		return false;
+
+	if ((u64)offset >= size)
+		return false;
+
+	/* Update offset relative to the start of the variable */
+	data->offset = offset;
+	return true;
+}
+
+/**
+ * is_breg_access_indirect - Check if breg based access implies type
+ * dereference
+ * @ops: DWARF operations array
+ * @nops: Number of operations in @ops
+ *
+ * Returns true if the DWARF expression evaluates to the variable's
+ * value, so the memory access on that register needs type dereference.
+ * Returns false if the expression evaluates to the variable's address.
+ * This is called after check_allowed_ops.
+ */
+static bool is_breg_access_indirect(Dwarf_Op *ops, size_t nops)
+{
+	/* only the base register */
+	if (nops == 1)
+		return false;
+
+	if (nops == 2 && ops[1].atom == DW_OP_stack_value)
+		return true;
+
+	if (nops == 3 && (ops[1].atom == DW_OP_deref ||
+		ops[1].atom == DW_OP_deref_size) &&
+		ops[2].atom == DW_OP_stack_value)
+		return false;
+	/* unreachable, OP not supported */
+	return false;
+}
+
+/* Only checks direct child DIEs in the given scope. */
+static int __die_find_var_reg_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct find_var_data *data = arg;
+	int tag = dwarf_tag(die_mem);
+	ptrdiff_t off = 0;
+	Dwarf_Attribute attr;
+	Dwarf_Addr base, start, end;
+	Dwarf_Op *ops;
+	size_t nops;
+
+	if (tag != DW_TAG_variable && tag != DW_TAG_formal_parameter)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	while ((off = dwarf_getlocations(&attr, off, &base, &start, &end, &ops, &nops)) > 0) {
+		/* Assuming the location list is sorted by address */
+		if (end <= data->pc)
+			continue;
+		if (start > data->pc)
+			break;
+
+		/* Local variables accessed using frame base register */
+		if (data->is_fbreg && ops->atom == DW_OP_fbreg &&
+		    check_allowed_ops(ops, nops) &&
+		    match_var_offset(die_mem, data, data->offset, ops->number,
+				     is_breg_access_indirect(ops, nops)))
+			return DIE_FIND_CB_END;
+
+		/* Only match with a simple case */
+		if (data->reg < DWARF_OP_DIRECT_REGS) {
+			/* pointer variables saved in a register 0 to 31 */
+			if (ops->atom == (DW_OP_reg0 + data->reg) &&
+			    check_allowed_ops(ops, nops) &&
+			    match_var_offset(die_mem, data, data->offset, 0,
+					     /*is_pointer=*/true))
+				return DIE_FIND_CB_END;
+
+			/* variables accessed by a register + offset */
+			if (ops->atom == (DW_OP_breg0 + data->reg) &&
+			    check_allowed_ops(ops, nops) &&
+			    match_var_offset(die_mem, data, data->offset, ops->number,
+					     is_breg_access_indirect(ops, nops)))
+				return DIE_FIND_CB_END;
+		} else {
+			/* pointer variables saved in a register 32 or above */
+			if (ops->atom == DW_OP_regx && ops->number == data->reg &&
+			    check_allowed_ops(ops, nops) &&
+			    match_var_offset(die_mem, data, data->offset, 0,
+					     /*is_pointer=*/true))
+				return DIE_FIND_CB_END;
+
+			/* variables accessed by a register + offset */
+			if (ops->atom == DW_OP_bregx && data->reg == ops->number &&
+			    check_allowed_ops(ops, nops) &&
+			    match_var_offset(die_mem, data, data->offset, ops->number2,
+					     is_breg_access_indirect(ops, nops)))
+				return DIE_FIND_CB_END;
+		}
+	}
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_find_variable_by_reg - Find a variable saved in a register
+ * @sc_die: a scope DIE
+ * @pc: the program address to find
+ * @reg: the register number to find
+ * @poffset: pointer to offset, will be updated for fbreg case
+ * @is_fbreg: boolean value if the current register is the frame base
+ * @die_mem: a buffer to save the resulting DIE
+ *
+ * Find the variable DIE accessed by the given register.  It'll update the @offset
+ * when the variable is in the stack.
+ */
+Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg,
+				    Dwarf_Die *type_die, int *poffset, bool is_fbreg,
+				    Dwarf_Die *die_mem)
+{
+	struct find_var_data data = {
+		.pc = pc,
+		.reg = reg,
+		.offset = *poffset,
+		.is_fbreg = is_fbreg,
+	};
+	Dwarf_Die *result;
+
+	result = die_find_child(sc_die, __die_find_var_reg_cb, &data, die_mem);
+	if (result) {
+		*poffset = data.offset;
+		*type_die = data.type;
+	}
+	return result;
+}
+
+/* Only checks direct child DIEs in the given scope */
+static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct find_var_data *data = arg;
+	int tag = dwarf_tag(die_mem);
+	ptrdiff_t off = 0;
+	Dwarf_Attribute attr;
+	Dwarf_Addr base, start, end;
+	Dwarf_Op *ops;
+	size_t nops;
+
+	if (tag != DW_TAG_variable)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	while ((off = dwarf_getlocations(&attr, off, &base, &start, &end, &ops, &nops)) > 0) {
+		if (ops->atom != DW_OP_addr)
+			continue;
+
+		if (check_allowed_ops(ops, nops) &&
+		    match_var_offset(die_mem, data, data->addr, ops->number,
+				     /*is_pointer=*/false))
+			return DIE_FIND_CB_END;
+	}
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_find_variable_by_addr - Find variable located at given address
+ * @sc_die: a scope DIE
+ * @addr: the data address to find
+ * @die_mem: a buffer to save the resulting DIE
+ * @offset: the offset in the resulting type
+ *
+ * Find the variable DIE located at the given address (in PC-relative mode).
+ * This is usually for global variables.
+ */
+Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr addr,
+				     Dwarf_Die *die_mem, Dwarf_Die *type_die,
+				     int *offset)
+{
+	struct find_var_data data = {
+		.addr = addr,
+	};
+	Dwarf_Die *result;
+
+	result = die_find_child(sc_die, __die_find_var_addr_cb, &data, die_mem);
+	if (result) {
+		*offset = data.offset;
+		*type_die = data.type;
+	}
+	return result;
+}
+
+static int __die_collect_vars_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct die_var_type **var_types = arg;
+	Dwarf_Die type_die;
+	int tag = dwarf_tag(die_mem);
+	Dwarf_Attribute attr;
+	Dwarf_Addr base, start, end = 0;
+	Dwarf_Op *ops;
+	size_t nops;
+	struct die_var_type *vt;
+	ptrdiff_t off;
+
+	if (tag != DW_TAG_variable && tag != DW_TAG_formal_parameter)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	if (__die_get_real_type(die_mem, &type_die) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	/*
+	 * Collect all location entries as variables may have different
+	 * locations across different address ranges.
+	 */
+	off = 0;
+	while ((off = dwarf_getlocations(&attr, off, &base, &start, &end, &ops, &nops)) > 0) {
+		if (!check_allowed_ops(ops, nops))
+			continue;
+
+		vt = malloc(sizeof(*vt));
+		if (vt == NULL)
+			return DIE_FIND_CB_END;
+
+		/* Usually a register holds the value of a variable */
+		vt->is_reg_var_addr = false;
+
+		if (((ops->atom >= DW_OP_breg0 && ops->atom <= DW_OP_breg31) ||
+		      ops->atom == DW_OP_bregx || ops->atom == DW_OP_fbreg) &&
+		      !is_breg_access_indirect(ops, nops))
+			/* The register contains an address of the variable. */
+			vt->is_reg_var_addr = true;
+
+		vt->die_off = dwarf_dieoffset(&type_die);
+		vt->addr = start;
+		vt->end = end;
+		vt->has_range = (end != 0 || start != 0);
+		vt->reg = reg_from_dwarf_op(ops);
+		vt->offset = offset_from_dwarf_op(ops);
+		vt->next = *var_types;
+		*var_types = vt;
+	}
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_collect_vars - Save all variables and parameters
+ * @sc_die: a scope DIE
+ * @var_types: a pointer to save the resulting list
+ *
+ * Save all variables and parameters in the @sc_die and save them to @var_types.
+ * The @var_types is a singly-linked list containing type and location info.
+ * Actual type can be retrieved using dwarf_offdie() with 'die_off' later.
+ *
+ * Callers should free @var_types.
+ */
+void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types)
+{
+	Dwarf_Die die_mem;
+
+	die_find_child(sc_die, __die_collect_vars_cb, (void *)var_types, &die_mem);
+}
+
+static int __die_collect_global_vars_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct die_var_type **var_types = arg;
+	Dwarf_Die type_die;
+	int tag = dwarf_tag(die_mem);
+	Dwarf_Attribute attr;
+	Dwarf_Addr base, start, end;
+	Dwarf_Op *ops;
+	size_t nops;
+	struct die_var_type *vt;
+
+	if (tag != DW_TAG_variable)
+		return DIE_FIND_CB_SIBLING;
+
+	if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	/* Only collect the location with an absolute address. */
+	if (dwarf_getlocations(&attr, 0, &base, &start, &end, &ops, &nops) <= 0)
+		return DIE_FIND_CB_SIBLING;
+
+	if (ops->atom != DW_OP_addr)
+		return DIE_FIND_CB_SIBLING;
+
+	if (!check_allowed_ops(ops, nops))
+		return DIE_FIND_CB_SIBLING;
+
+	if (die_get_real_type(die_mem, &type_die) == NULL)
+		return DIE_FIND_CB_SIBLING;
+
+	vt = malloc(sizeof(*vt));
+	if (vt == NULL)
+		return DIE_FIND_CB_END;
+
+	vt->die_off = dwarf_dieoffset(&type_die);
+	vt->addr = ops->number;
+	vt->end = 0;
+	vt->has_range = false;
+	vt->reg = -1;
+	vt->offset = 0;
+	vt->next = *var_types;
+	*var_types = vt;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_collect_global_vars - Save all global variables
+ * @cu_die: a CU DIE
+ * @var_types: a pointer to save the resulting list
+ *
+ * Save all global variables in the @cu_die and save them to @var_types.
+ * The @var_types is a singly-linked list containing type and location info.
+ * Actual type can be retrieved using dwarf_offdie() with 'die_off' later.
+ *
+ * Callers should free @var_types.
+ */
+void die_collect_global_vars(Dwarf_Die *cu_die, struct die_var_type **var_types)
+{
+	Dwarf_Die die_mem;
+
+	die_find_child(cu_die, __die_collect_global_vars_cb, (void *)var_types, &die_mem);
+}
+
+/**
+ * die_get_cfa - Get frame base information
+ * @dwarf: a Dwarf info
+ * @pc: program address
+ * @preg: pointer for saved register
+ * @poffset: pointer for saved offset
+ *
+ * This function gets register and offset for CFA (Canonical Frame Address)
+ * by searching the CIE/FDE info.  The CFA usually points to the start address
+ * of the current stack frame and local variables can be located using an offset
+ * from the CFA.  The @preg and @poffset will be updated if it returns 0.
+ */
+int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset)
+{
+	Dwarf_CFI *cfi;
+	Dwarf_Frame *frame = NULL;
+	Dwarf_Op *ops = NULL;
+	size_t nops;
+
+	cfi = dwarf_getcfi(dwarf);
+	if (cfi == NULL)
+		return -1;
+
+	if (!dwarf_cfi_addrframe(cfi, pc, &frame) &&
+	    !dwarf_frame_cfa(frame, &ops, &nops) &&
+	    check_allowed_ops(ops, nops)) {
+		*preg = reg_from_dwarf_op(ops);
+		*poffset = offset_from_dwarf_op(ops);
+		return 0;
+	}
+	return -1;
+}
+
+/*
+ * die_has_loclist - Check if DW_AT_location of @vr_die is a location list
+ * @vr_die: a variable DIE
+ */
+static bool die_has_loclist(Dwarf_Die *vr_die)
+{
+	Dwarf_Attribute loc;
+	int tag = dwarf_tag(vr_die);
+
+	if (tag != DW_TAG_formal_parameter &&
+	    tag != DW_TAG_variable)
+		return false;
+
+	return (dwarf_attr_integrate(vr_die, DW_AT_location, &loc) &&
+		dwarf_whatform(&loc) == DW_FORM_sec_offset);
+}
+
+/*
+ * die_is_optimized_target - Check if target program is compiled with
+ * optimization
+ * @cu_die: a CU DIE
+ *
+ * For any object in given CU whose DW_AT_location is a location list,
+ * target program is compiled with optimization. This is applicable to
+ * clang as well.
+ */
+bool die_is_optimized_target(Dwarf_Die *cu_die)
+{
+	Dwarf_Die tmp_die;
+
+	if (die_has_loclist(cu_die))
+		return true;
+
+	if (!dwarf_child(cu_die, &tmp_die) &&
+	    die_is_optimized_target(&tmp_die))
+		return true;
+
+	if (!dwarf_siblingof(cu_die, &tmp_die) &&
+	    die_is_optimized_target(&tmp_die))
+		return true;
+
+	return false;
+}
+
+/*
+ * die_search_idx - Search index of given line address
+ * @lines: Line records of single CU
+ * @nr_lines: Number of @lines
+ * @addr: address we are looking for
+ * @idx: index to be set by this function (return value)
+ *
+ * Search for @addr by looping over every lines of CU. If address
+ * matches, set index of that line in @idx. Note that single source
+ * line can have multiple line records. i.e. single source line can
+ * have multiple index.
+ */
+static bool die_search_idx(Dwarf_Lines *lines, unsigned long nr_lines,
+			   Dwarf_Addr addr, unsigned long *idx)
+{
+	unsigned long i;
+	Dwarf_Addr tmp;
+
+	for (i = 0; i < nr_lines; i++) {
+		if (dwarf_lineaddr(dwarf_onesrcline(lines, i), &tmp))
+			return false;
+
+		if (tmp == addr) {
+			*idx = i;
+			return true;
+		}
+	}
+	return false;
+}
+
+/*
+ * die_get_postprologue_addr - Search next address after function prologue
+ * @entrypc_idx: entrypc index
+ * @lines: Line records of single CU
+ * @nr_lines: Number of @lines
+ * @hignpc: high PC address of function
+ * @postprologue_addr: Next address after function prologue (return value)
+ *
+ * Look for prologue-end marker. If there is no explicit marker, return
+ * address of next line record or next source line.
+ */
+static bool die_get_postprologue_addr(unsigned long entrypc_idx,
+				      Dwarf_Lines *lines,
+				      unsigned long nr_lines,
+				      Dwarf_Addr highpc,
+				      Dwarf_Addr *postprologue_addr)
+{
+	unsigned long i;
+	int entrypc_lno, lno;
+	Dwarf_Line *line;
+	Dwarf_Addr addr;
+	bool p_end;
+
+	/* entrypc_lno is actual source line number */
+	line = dwarf_onesrcline(lines, entrypc_idx);
+	if (dwarf_lineno(line, &entrypc_lno))
+		return false;
+
+	for (i = entrypc_idx; i < nr_lines; i++) {
+		line = dwarf_onesrcline(lines, i);
+
+		if (dwarf_lineaddr(line, &addr) ||
+		    dwarf_lineno(line, &lno)    ||
+		    dwarf_lineprologueend(line, &p_end))
+			return false;
+
+		/* highpc is exclusive. [entrypc,highpc) */
+		if (addr >= highpc)
+			break;
+
+		/* clang supports prologue-end marker */
+		if (p_end)
+			break;
+
+		/* Actual next line in source */
+		if (lno != entrypc_lno)
+			break;
+
+		/*
+		 * Single source line can have multiple line records.
+		 * For Example,
+		 *     void foo() { printf("hello\n"); }
+		 * contains two line records. One points to declaration and
+		 * other points to printf() line. Variable 'lno' won't get
+		 * incremented in this case but 'i' will.
+		 */
+		if (i != entrypc_idx)
+			break;
+	}
+
+	if (dwarf_lineaddr(line, postprologue_addr) != 0)
+		return false;
+	if (*postprologue_addr >= highpc) {
+		if (dwarf_lineaddr(dwarf_onesrcline(lines, i - 1), postprologue_addr) != 0)
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * die_skip_prologue - Use next address after prologue as probe location
+ * @sp_die: a subprogram DIE
+ * @cu_die: a CU DIE
+ * @entrypc: entrypc of the function
+ *
+ * Function prologue prepares stack and registers before executing function
+ * logic. When target program is compiled without optimization, function
+ * parameter information is only valid after prologue. When we probe entrypc
+ * of the function, and try to record function parameter, it contains
+ * garbage value.
+ */
+void die_skip_prologue(Dwarf_Die *sp_die, Dwarf_Die *cu_die,
+		       Dwarf_Addr *entrypc)
+{
+	size_t nr_lines = 0;
+	unsigned long entrypc_idx = 0;
+	Dwarf_Lines *lines = NULL;
+	Dwarf_Addr postprologue_addr;
+	Dwarf_Addr highpc;
+
+	if (dwarf_highpc(sp_die, &highpc))
+		return;
+
+	if (dwarf_getsrclines(cu_die, &lines, &nr_lines))
+		return;
+
+	if (!die_search_idx(lines, nr_lines, *entrypc, &entrypc_idx))
+		return;
+
+	if (!die_get_postprologue_addr(entrypc_idx, lines, nr_lines,
+				       highpc, &postprologue_addr))
+		return;
+
+	*entrypc = postprologue_addr;
+}
+
+/* Internal parameters for __die_find_scope_cb() */
+struct find_scope_data {
+	/* Target instruction address */
+	Dwarf_Addr pc;
+	/* Number of scopes found [output] */
+	int nr;
+	/* Array of scopes found, 0 for the outermost one. [output] */
+	Dwarf_Die *scopes;
+};
+
+static int __die_find_scope_cb(Dwarf_Die *die_mem, void *arg)
+{
+	struct find_scope_data *data = arg;
+	int tag = dwarf_tag(die_mem);
+
+	if (dwarf_haspc(die_mem, data->pc)) {
+		Dwarf_Die *tmp;
+
+		tmp = realloc(data->scopes, (data->nr + 1) * sizeof(*tmp));
+		if (tmp == NULL)
+			return DIE_FIND_CB_END;
+
+		memcpy(tmp + data->nr, die_mem, sizeof(*die_mem));
+		data->scopes = tmp;
+		data->nr++;
+		return DIE_FIND_CB_CHILD;
+	}
+
+	/*
+	 * If the DIE doesn't have the PC, we still need to check its children
+	 * and siblings if it's a container like a namespace.
+	 */
+	if (tag == DW_TAG_namespace)
+		return DIE_FIND_CB_CONTINUE;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_get_scopes - Return a list of scopes including the address
+ * @cu_die: a compile unit DIE
+ * @pc: the address to find
+ * @scopes: the array of DIEs for scopes (result)
+ *
+ * This function does the same as the dwarf_getscopes() but doesn't follow
+ * the origins of inlined functions.  It returns the number of scopes saved
+ * in the @scopes argument.  The outer scope will be saved first (index 0) and
+ * the last one is the innermost scope at the @pc.
+ */
+int die_get_scopes(Dwarf_Die *cu_die, Dwarf_Addr pc, Dwarf_Die **scopes)
+{
+	struct find_scope_data data = {
+		.pc = pc,
+	};
+	Dwarf_Die die_mem;
+
+	die_find_child(cu_die, __die_find_scope_cb, &data, &die_mem);
+
+	*scopes = data.scopes;
+	return data.nr;
+}
+
+static int __die_find_member_offset_cb(Dwarf_Die *die_mem, void *arg)
+{
+	Dwarf_Die type_die;
+	Dwarf_Word size, loc;
+	Dwarf_Word offset = (long)arg;
+	int tag = dwarf_tag(die_mem);
+
+	if (tag != DW_TAG_member)
+		return DIE_FIND_CB_SIBLING;
+
+	/* Unions might not have location */
+	if (die_get_data_member_location(die_mem, &loc) < 0) {
+		Dwarf_Attribute attr;
+
+		if (dwarf_attr_integrate(die_mem, DW_AT_data_bit_offset, &attr) &&
+		    dwarf_formudata(&attr, &loc) == 0)
+			loc /= 8;
+		else
+			loc = 0;
+	}
+
+	if (offset == loc)
+		return DIE_FIND_CB_END;
+
+	if (die_get_real_type(die_mem, &type_die) == NULL) {
+		// TODO: add a pr_debug_dtp() later for this unlikely failure
+		return DIE_FIND_CB_SIBLING;
+	}
+
+	if (dwarf_aggregate_size(&type_die, &size) < 0)
+		size = 0;
+
+	if (loc < offset && offset < (loc + size))
+		return DIE_FIND_CB_END;
+
+	return DIE_FIND_CB_SIBLING;
+}
+
+/**
+ * die_get_member_type - Return type info of struct member
+ * @type_die: a type DIE
+ * @offset: offset in the type
+ * @die_mem: a buffer to save the resulting DIE
+ *
+ * This function returns a type of a member in @type_die where it's located at
+ * @offset if it's a struct.  For now, it just returns the first matching
+ * member in a union.  For other types, it'd return the given type directly
+ * if it's within the size of the type or NULL otherwise.
+ */
+Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
+			       Dwarf_Die *die_mem)
+{
+	Dwarf_Die *member;
+	Dwarf_Die mb_type;
+	int tag;
+
+	tag = dwarf_tag(type_die);
+	/* If it's not a compound type, return the type directly */
+	if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
+		Dwarf_Word size;
+
+		if (dwarf_aggregate_size(type_die, &size) < 0)
+			size = 0;
+
+		if ((unsigned)offset >= size)
+			return NULL;
+
+		*die_mem = *type_die;
+		return die_mem;
+	}
+
+	mb_type = *type_die;
+	/* TODO: Handle union types better? */
+	while (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
+		member = die_find_child(&mb_type, __die_find_member_offset_cb,
+					(void *)(long)offset, die_mem);
+		if (member == NULL)
+			return NULL;
+
+		if (die_get_real_type(member, &mb_type) == NULL)
+			return NULL;
+
+		tag = dwarf_tag(&mb_type);
+
+		if (tag == DW_TAG_structure_type || tag == DW_TAG_union_type ||
+		    tag == DW_TAG_array_type) {
+			Dwarf_Word loc;
+
+			/* Update offset for the start of the member struct */
+			if (die_get_data_member_location(member, &loc) == 0)
+				offset -= loc;
+		}
+
+		/* Handle array types: resolve to the element type by one level */
+		if (tag == DW_TAG_array_type) {
+			Dwarf_Word size;
+
+			if (die_get_real_type(&mb_type, &mb_type) == NULL)
+				return NULL;
+
+			if (dwarf_aggregate_size(&mb_type, &size) < 0)
+				return NULL;
+
+			offset = offset % size;
+			tag = dwarf_tag(&mb_type);
+		}
+	}
+	*die_mem = mb_type;
+	return die_mem;
+}
+
+/**
+ * die_deref_ptr_type - Return type info for pointer access
+ * @ptr_die: a pointer type DIE
+ * @offset: access offset for the pointer
+ * @die_mem: a buffer to save the resulting DIE
+ *
+ * This function follows the pointer in @ptr_die with given @offset
+ * and saves the resulting type in @die_mem.  If the pointer points
+ * a struct type, actual member at the offset would be returned.
+ */
+Dwarf_Die *die_deref_ptr_type(Dwarf_Die *ptr_die, int offset,
+			      Dwarf_Die *die_mem)
+{
+	Dwarf_Die type_die;
+
+	if (dwarf_tag(ptr_die) != DW_TAG_pointer_type)
+		return NULL;
+
+	if (die_get_real_type(ptr_die, &type_die) == NULL)
+		return NULL;
+
+	return die_get_member_type(&type_die, offset, die_mem);
+}