ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 242 insertions, 0 deletions

diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
new file mode 100644
index 000000000..4ca7e7e4f
--- /dev/null
+++ b/tools/perf/util/libdw.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "dso.h"
+#include "libdw.h"
+#include "srcline.h"
+#include "symbol.h"
+#include "dwarf-aux.h"
+#include "callchain.h"
+#include <fcntl.h>
+#include <unistd.h>
+#include <elfutils/libdwfl.h>
+
+static const Dwfl_Callbacks offline_callbacks = {
+	.find_debuginfo = dwfl_standard_find_debuginfo,
+	.section_address = dwfl_offline_section_address,
+	.find_elf = dwfl_build_id_find_elf,
+};
+
+void dso__free_libdw(struct dso *dso)
+{
+	Dwfl *dwfl = dso__libdw(dso);
+
+	if (dwfl) {
+		dwfl_end(dwfl);
+		dso__set_libdw(dso, NULL);
+	}
+}
+
+struct Dwfl *dso__libdw_dwfl(struct dso *dso)
+{
+	Dwfl *dwfl = dso__libdw(dso);
+	const char *dso_name;
+	Dwfl_Module *mod;
+	int fd;
+
+	if (dwfl)
+		return dwfl;
+
+	dso_name = dso__long_name(dso);
+	/*
+	 * Initialize Dwfl session.
+	 * We need to open the DSO file to report it to libdw.
+	 */
+	fd = open(dso_name, O_RDONLY);
+	if (fd < 0)
+		return NULL;
+
+	dwfl = dwfl_begin(&offline_callbacks);
+	if (!dwfl) {
+		close(fd);
+		return NULL;
+	}
+
+	/*
+	 * If the report is successful, the file descriptor fd is consumed
+	 * and closed by the Dwfl. If not, it is not closed.
+	 */
+	mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
+	if (!mod) {
+		dwfl_end(dwfl);
+		close(fd);
+		return NULL;
+	}
+
+	if (dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL) != 0) {
+		dwfl_end(dwfl);
+		return NULL;
+	}
+	dso__set_libdw(dso, dwfl);
+
+	return dwfl;
+}
+
+struct libdw_a2l_cb_args {
+	struct dso *dso;
+	struct symbol *sym;
+	struct inline_node *node;
+	char *leaf_srcline;
+	bool leaf_srcline_used;
+	int err;
+};
+
+static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
+{
+	struct libdw_a2l_cb_args *args  = _args;
+	const char *call_fname = die_get_call_file(die);
+	int call_lineno = die_get_call_lineno(die);
+	char *call_srcline = srcline__unknown;
+	struct symbol *inline_sym;
+
+	if (dwarf_tag(die) == DW_TAG_subprogram && args->sym) {
+		/*
+		 * cu_walk_functions_at() opens the walk with the
+		 * containing DW_TAG_subprogram DIE (the non-inlined outer
+		 * function). That's just the base symbol -- use it
+		 * directly. Avoids a fragile name-vs-name compare in
+		 * new_inline_sym() that misfires when GCC IPA passes
+		 * (.isra/.constprop/.part/.cold) rename the ELF symbol
+		 * while DWARF keeps the pre-clone linkage name, which
+		 * left the outer frame spuriously tagged "(inlined)".
+		 */
+		inline_sym = args->sym;
+	} else {
+		/*
+		 * Prefer DW_AT_linkage_name so C++ inline frames keep
+		 * their namespace/class qualification. new_inline_sym()
+		 * runs the name through dso__demangle_sym(), so the
+		 * mangled linkage name is turned back into
+		 * "Namespace::Class::method". Fall back to DW_AT_name
+		 * (unqualified) when no linkage name is present, e.g.
+		 * for C code or extern "C" functions.
+		 */
+		const char *funcname = die_get_linkage_name(die) ?: die_name(die);
+
+		inline_sym = new_inline_sym(args->dso, args->sym, funcname);
+		if (!inline_sym)
+			goto abort_enomem;
+	}
+
+	/* Assign caller information to the parent. */
+	if (call_fname)
+		call_srcline = srcline_from_fileline(call_fname, call_lineno >= 0 ? call_lineno : 0);
+
+	if (!list_empty(&args->node->val)) {
+		struct inline_list *parent;
+
+		if (callchain_param.order == ORDER_CALLEE)
+			parent = list_first_entry(&args->node->val, struct inline_list, list);
+		else
+			parent = list_last_entry(&args->node->val, struct inline_list, list);
+
+		if (args->leaf_srcline == parent->srcline)
+			args->leaf_srcline_used = false;
+		else if (parent->srcline != srcline__unknown)
+			free(parent->srcline);
+		parent->srcline = call_srcline;
+		call_srcline = NULL;
+	}
+	if (call_srcline && call_srcline != srcline__unknown)
+		free(call_srcline);
+
+	/* Add this symbol to the chain as the leaf. */
+	if (!args->leaf_srcline_used) {
+		if (inline_list__append_tail(inline_sym, args->leaf_srcline, args->node) != 0)
+			goto abort_delete_sym;
+		args->leaf_srcline_used = true;
+	} else {
+		char *srcline = strdup(args->leaf_srcline);
+
+		if (!srcline)
+			goto abort_delete_sym;
+		if (inline_list__append_tail(inline_sym, srcline, args->node) != 0) {
+			free(srcline);
+			goto abort_delete_sym;
+		}
+	}
+	return 0;
+
+abort_delete_sym:
+	if (symbol__inlined(inline_sym))
+		symbol__delete(inline_sym);
+abort_enomem:
+	args->err = -ENOMEM;
+	return DWARF_CB_ABORT;
+}
+
+int libdw__addr2line(u64 addr, char **file, unsigned int *line_nr,
+		     struct dso *dso, bool unwind_inlines,
+		     struct inline_node *node, struct symbol *sym)
+{
+	Dwfl *dwfl = dso__libdw_dwfl(dso);
+	Dwfl_Module *mod;
+	Dwfl_Line *dwline;
+	Dwarf_Addr bias;
+	const char *src;
+	int lineno = 0;
+
+	if (!dwfl)
+		return 0;
+
+	mod = dwfl_addrmodule(dwfl, addr);
+	if (!mod)
+		return 0;
+
+	/*
+	 * Get/ignore the dwarf information. Determine the bias, difference
+	 * between the regular ELF addr2line addresses and those to use with
+	 * libdw.
+	 */
+	if (!dwfl_module_getdwarf(mod, &bias))
+		return 0;
+
+	/* Find source line information for the address. */
+	dwline = dwfl_module_getsrc(mod, addr + bias);
+	if (!dwline)
+		return 0;
+
+	/* Get line information. */
+	src = dwfl_lineinfo(dwline, /*addr=*/NULL, &lineno, /*col=*/NULL, /*mtime=*/NULL,
+			    /*length=*/NULL);
+
+	if (file)
+		*file = src ? strdup(src) : NULL;
+	if (line_nr)
+		*line_nr = lineno;
+
+	/* Optionally unwind inline function call chain. */
+	if (unwind_inlines && node) {
+		Dwarf_Addr unused_bias;
+		Dwarf_Die *cudie = dwfl_module_addrdie(mod, addr + bias, &unused_bias);
+		struct libdw_a2l_cb_args args = {
+			.dso = dso,
+			.sym = sym,
+			.node = node,
+			.leaf_srcline = srcline_from_fileline(src ?: "<unknown>", lineno),
+		};
+
+		if (!args.leaf_srcline) {
+			if (file && *file) {
+				free(*file);
+				*file = NULL;
+			}
+			return 0;
+		}
+
+		/* Walk from the parent down to the leaf. */
+		if (cudie)
+			cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);
+
+		if (!args.leaf_srcline_used)
+			free(args.leaf_srcline);
+
+		if (args.err) {
+			if (file && *file) {
+				free(*file);
+				*file = NULL;
+			}
+			inline_node__clear_frames(node);
+			return 0;
+		}
+	}
+	return 1;
+}