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, 279 insertions, 0 deletions

diff --git a/tools/perf/util/llvm.c b/tools/perf/util/llvm.c
new file mode 100644
index 000000000..a0deb742a
--- /dev/null
+++ b/tools/perf/util/llvm.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "llvm.h"
+#include "annotate.h"
+#include "debug.h"
+#include "dso.h"
+#include "map.h"
+#include "namespaces.h"
+#include "srcline.h"
+#include "symbol.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <linux/zalloc.h>
+
+#ifdef HAVE_LIBLLVM_SUPPORT
+#include "llvm-c-helpers.h"
+#include <llvm-c/Disassembler.h>
+#include <llvm-c/Target.h>
+#endif
+
+#ifdef HAVE_LIBLLVM_SUPPORT
+static void free_llvm_inline_frames(struct llvm_a2l_frame *inline_frames,
+				    int num_frames)
+{
+	if (inline_frames != NULL) {
+		for (int i = 0; i < num_frames; ++i) {
+			zfree(&inline_frames[i].filename);
+			zfree(&inline_frames[i].funcname);
+		}
+		zfree(&inline_frames);
+	}
+}
+#endif
+
+int llvm__addr2line(const char *dso_name __maybe_unused, u64 addr __maybe_unused,
+		     char **file __maybe_unused, unsigned int *line __maybe_unused,
+		     struct dso *dso __maybe_unused, bool unwind_inlines __maybe_unused,
+		     struct inline_node *node __maybe_unused, struct symbol *sym __maybe_unused)
+{
+#ifdef HAVE_LIBLLVM_SUPPORT
+	struct llvm_a2l_frame *inline_frames = NULL;
+	int num_frames = llvm_addr2line(dso_name, addr, file, line,
+					node && unwind_inlines, &inline_frames);
+
+	if (num_frames == 0 || !inline_frames) {
+		/* Error, or we didn't want inlines. */
+		return num_frames;
+	}
+
+	for (int i = 0; i < num_frames; ++i) {
+		struct symbol *inline_sym =
+			new_inline_sym(dso, sym, inline_frames[i].funcname);
+		char *srcline = NULL;
+
+		if (inline_frames[i].filename) {
+			srcline =
+				srcline_from_fileline(inline_frames[i].filename,
+						      inline_frames[i].line);
+		}
+		if (inline_list__append(inline_sym, srcline, node) != 0) {
+			free_llvm_inline_frames(inline_frames, num_frames);
+			return 0;
+		}
+	}
+	free_llvm_inline_frames(inline_frames, num_frames);
+
+	return num_frames;
+#else
+	return -1;
+#endif
+}
+
+#ifdef HAVE_LIBLLVM_SUPPORT
+static void init_llvm(void)
+{
+	static bool init;
+
+	if (!init) {
+		LLVMInitializeAllTargetInfos();
+		LLVMInitializeAllTargetMCs();
+		LLVMInitializeAllDisassemblers();
+		init = true;
+	}
+}
+
+/*
+ * Whenever LLVM wants to resolve an address into a symbol, it calls this
+ * callback. We don't ever actually _return_ anything (in particular, because
+ * it puts quotation marks around what we return), but we use this as a hint
+ * that there is a branch or PC-relative address in the expression that we
+ * should add some textual annotation for after the instruction. The caller
+ * will use this information to add the actual annotation.
+ */
+struct symbol_lookup_storage {
+	u64 branch_addr;
+	u64 pcrel_load_addr;
+};
+
+static const char *
+symbol_lookup_callback(void *disinfo, uint64_t value,
+		       uint64_t *ref_type,
+		       uint64_t address __maybe_unused,
+		       const char **ref __maybe_unused)
+{
+	struct symbol_lookup_storage *storage = disinfo;
+
+	if (*ref_type == LLVMDisassembler_ReferenceType_In_Branch)
+		storage->branch_addr = value;
+	else if (*ref_type == LLVMDisassembler_ReferenceType_In_PCrel_Load)
+		storage->pcrel_load_addr = value;
+	*ref_type = LLVMDisassembler_ReferenceType_InOut_None;
+	return NULL;
+}
+#endif
+
+int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
+			     struct annotate_args *args __maybe_unused)
+{
+#ifdef HAVE_LIBLLVM_SUPPORT
+	struct annotation *notes = symbol__annotation(sym);
+	struct map *map = args->ms->map;
+	struct dso *dso = map__dso(map);
+	u64 start = map__rip_2objdump(map, sym->start);
+	/* Malloc-ed buffer containing instructions read from disk. */
+	u8 *code_buf = NULL;
+	/* Pointer to code to be disassembled. */
+	const u8 *buf;
+	u64 buf_len;
+	u64 pc;
+	bool is_64bit;
+	char disasm_buf[2048];
+	size_t disasm_len;
+	struct disasm_line *dl;
+	LLVMDisasmContextRef disasm = NULL;
+	struct symbol_lookup_storage storage;
+	char *line_storage = NULL;
+	size_t line_storage_len = 0;
+	int ret = -1;
+
+	if (args->options->objdump_path)
+		return -1;
+
+	buf = dso__read_symbol(dso, filename, map, sym,
+			       &code_buf, &buf_len, &is_64bit);
+	if (buf == NULL)
+		return errno;
+
+	init_llvm();
+	if (arch__is_x86(args->arch)) {
+		const char *triplet = is_64bit ? "x86_64-pc-linux" : "i686-pc-linux";
+
+		disasm = LLVMCreateDisasm(triplet, &storage, /*tag_type=*/0,
+					  /*get_op_info=*/NULL, symbol_lookup_callback);
+	} else {
+		char triplet[64];
+		const char *features = NULL;
+
+		scnprintf(triplet, sizeof(triplet), "%s-linux-gnu",
+			  args->arch->name);
+		if (args->arch->id.e_machine == EM_AARCH64)
+			features = "+all";
+		disasm = LLVMCreateDisasmCPUFeatures(triplet, /*cpu=*/"",
+						     features, &storage,
+						     /*tag_type=*/0,
+						     /*get_op_info=*/NULL,
+						     symbol_lookup_callback);
+	}
+
+	if (disasm == NULL)
+		goto err;
+
+	if (args->options->disassembler_style &&
+	    !strcmp(args->options->disassembler_style, "intel"))
+		LLVMSetDisasmOptions(disasm,
+				     LLVMDisassembler_Option_AsmPrinterVariant);
+
+	/*
+	 * This needs to be set after AsmPrinterVariant, due to a bug in LLVM;
+	 * setting AsmPrinterVariant makes a new instruction printer, making it
+	 * forget about the PrintImmHex flag (which is applied before if both
+	 * are given to the same call).
+	 */
+	LLVMSetDisasmOptions(disasm, LLVMDisassembler_Option_PrintImmHex);
+
+	/* add the function address and name */
+	scnprintf(disasm_buf, sizeof(disasm_buf), "%#"PRIx64" <%s>:",
+		  start, sym->name);
+
+	args->offset = -1;
+	args->line = disasm_buf;
+	args->line_nr = 0;
+	args->fileloc = NULL;
+	args->ms->sym = sym;
+
+	dl = disasm_line__new(args);
+	if (dl == NULL)
+		goto err;
+
+	annotation_line__add(&dl->al, &notes->src->source);
+
+	pc = start;
+	for (u64 offset = 0; offset < buf_len; ) {
+		unsigned int ins_len;
+
+		storage.branch_addr = 0;
+		storage.pcrel_load_addr = 0;
+
+		/*
+		 * LLVM's API has the code be disassembled as non-const, cast
+		 * here as we may be disassembling from mapped read-only memory.
+		 */
+		ins_len = LLVMDisasmInstruction(disasm, (u8 *)(buf + offset),
+						buf_len - offset, pc,
+						disasm_buf, sizeof(disasm_buf));
+		if (ins_len == 0)
+			goto err;
+		disasm_len = strlen(disasm_buf);
+
+		if (storage.branch_addr != 0) {
+			char *name = llvm_name_for_code(dso, filename,
+							storage.branch_addr);
+			if (name != NULL) {
+				disasm_len += scnprintf(disasm_buf + disasm_len,
+							sizeof(disasm_buf) -
+								disasm_len,
+							" <%s>", name);
+				free(name);
+			}
+		}
+		if (storage.pcrel_load_addr != 0) {
+			char *name = llvm_name_for_data(dso, filename,
+							storage.pcrel_load_addr);
+			disasm_len += scnprintf(disasm_buf + disasm_len,
+						sizeof(disasm_buf) - disasm_len,
+						"  # %#"PRIx64,
+						storage.pcrel_load_addr);
+			if (name) {
+				disasm_len += scnprintf(disasm_buf + disasm_len,
+							sizeof(disasm_buf) -
+							disasm_len,
+							" <%s>", name);
+				free(name);
+			}
+		}
+
+		args->offset = offset;
+		args->line = expand_tabs(disasm_buf, &line_storage,
+					 &line_storage_len);
+		args->line_nr = 0;
+		args->fileloc = NULL;
+		args->ms->sym = sym;
+
+		llvm_addr2line(filename, pc, &args->fileloc,
+			       (unsigned int *)&args->line_nr, false, NULL);
+
+		dl = disasm_line__new(args);
+		if (dl == NULL)
+			goto err;
+
+		annotation_line__add(&dl->al, &notes->src->source);
+
+		free(args->fileloc);
+		pc += ins_len;
+		offset += ins_len;
+	}
+
+	ret = 0;
+
+err:
+	LLVMDisasmDispose(disasm);
+	free(code_buf);
+	free(line_storage);
+	return ret;
+#else // HAVE_LIBLLVM_SUPPORT
+	pr_debug("The LLVM disassembler isn't linked in for %s in %s\n",
+		 sym->name, filename);
+	return -1;
+#endif
+}