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, 347 insertions, 0 deletions

diff --git a/tools/objtool/klp-checksum.c b/tools/objtool/klp-checksum.c
new file mode 100644
index 000000000..b8e47f289
--- /dev/null
+++ b/tools/objtool/klp-checksum.c
@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <string.h>
+#include <subcmd/parse-options.h>
+
+#include <objtool/arch.h>
+#include <objtool/builtin.h>
+#include <objtool/check.h>
+#include <objtool/elf.h>
+#include <objtool/klp.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+#include <objtool/checksum.h>
+
+static int checksum_debug_init(struct objtool_file *file)
+{
+	char *dup, *s;
+
+	if (!opts.debug_checksum)
+		return 0;
+
+	dup = strdup(opts.debug_checksum);
+	if (!dup) {
+		ERROR_GLIBC("strdup");
+		return -1;
+	}
+
+	s = dup;
+	while (*s) {
+		bool found = false;
+		struct symbol *sym;
+		char *comma;
+
+		comma = strchr(s, ',');
+		if (comma)
+			*comma = '\0';
+
+		for_each_sym_by_name(file->elf, s, sym) {
+			if (!is_func_sym(sym) && !is_object_sym(sym))
+				continue;
+			sym->debug_checksum = 1;
+			found = true;
+		}
+
+		if (!found)
+			WARN("--debug-checksum: can't find '%s'", s);
+
+		if (!comma)
+			break;
+
+		s = comma + 1;
+	}
+
+	free(dup);
+	return 0;
+}
+
+static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
+				 struct instruction *insn)
+{
+	struct reloc *reloc = insn_reloc(file, insn);
+	struct alternative *alt;
+	unsigned long offset;
+	struct symbol *sym;
+	static bool in_alt;
+
+	if (insn->fake)
+		return;
+
+	if (!reloc) {
+		struct symbol *call_dest = insn_call_dest(insn);
+		struct instruction *jump_dest = insn->jump_dest;
+
+		/*
+		 * For a jump/call non-relocated dest offset embedded in the
+		 * instruction, the offset may vary due to changes in
+		 * surrounding code.  Just hash the opcode and a
+		 * position-independent representation of the destination.
+		 */
+
+		if (call_dest || jump_dest) {
+			unsigned char buf[16];
+			size_t len;
+
+			len = arch_jump_opcode_bytes(file, insn, buf);
+			__checksum_update_insn(func, insn, buf, len);
+
+			if (call_dest) {
+				__checksum_update_insn(func, insn, call_dest->demangled_name,
+						       strlen(call_dest->demangled_name));
+
+			} else if (jump_dest) {
+				struct symbol *dest_sym;
+				unsigned long offset;
+
+				/*
+				 * use insn->_sym instead of insn_sym() here.
+				 * For alternative replacements, the latter
+				 * would give the function of the code being
+				 * replaced.
+				 */
+				dest_sym = jump_dest->_sym;
+				if (!dest_sym)
+					goto alts;
+
+				__checksum_update_insn(func, insn, dest_sym->demangled_name,
+						       strlen(dest_sym->demangled_name));
+
+				offset = jump_dest->offset - dest_sym->offset;
+				__checksum_update_insn(func, insn, &offset, sizeof(offset));
+			}
+
+			goto alts;
+		}
+	}
+
+	__checksum_update_insn(func, insn, insn->sec->data->d_buf + insn->offset, insn->len);
+
+	if (!reloc)
+		goto alts;
+
+	sym = reloc->sym;
+	offset = arch_insn_adjusted_addend(insn, reloc);
+
+	if (is_string_sec(sym->sec)) {
+		char *str;
+
+		str = sym->sec->data->d_buf + sym->offset + offset;
+		__checksum_update_insn(func, insn, str, strlen(str));
+		goto alts;
+	}
+
+	if (is_sec_sym(sym)) {
+		sym = find_symbol_containing(reloc->sym->sec, offset);
+		if (!sym)
+			goto alts;
+
+		offset -= sym->offset;
+	}
+
+	__checksum_update_insn(func, insn, sym->demangled_name,
+			       strlen(sym->demangled_name));
+	__checksum_update_insn(func, insn, &offset, sizeof(offset));
+
+alts:
+	for (alt = insn->alts; alt; alt = alt->next) {
+		struct alt_group *alt_group = alt->insn->alt_group;
+
+		/* Prevent __ex_table recursion, e.g. LOAD_SEGMENT() */
+		if (in_alt)
+			break;
+		in_alt = true;
+
+		__checksum_update_insn(func, insn, &alt->type,
+				       sizeof(alt->type));
+
+		if (alt_group && alt_group->orig_group) {
+			struct instruction *alt_insn;
+
+			__checksum_update_insn(func, insn, &alt_group->feature,sizeof(alt_group->feature));
+
+			for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
+				checksum_update_insn(file, func, alt_insn);
+				if (!alt_group->last_insn || alt_insn == alt_group->last_insn)
+					break;
+			}
+		} else {
+			checksum_update_insn(file, func, alt->insn);
+		}
+
+		in_alt = false;
+	}
+}
+
+static void checksum_update_object(struct objtool_file *file, struct symbol *sym)
+{
+	struct reloc *reloc;
+
+	__checksum_update_object(sym, 0, "len", &sym->len, sizeof(sym->len));
+
+	if (sym->sec->data->d_buf)
+		__checksum_update_object(sym, 0, "data",
+					 sym->sec->data->d_buf + sym->offset,
+					 sym->len);
+
+	sym_for_each_reloc(file->elf, sym, reloc) {
+		unsigned long sym_offset = reloc_offset(reloc) - sym->offset;
+		struct symbol *target = reloc->sym;
+		s64 offset;
+
+		offset = reloc_addend(reloc);
+
+		if (is_string_sec(target->sec)) {
+			char *str;
+
+			str = target->sec->data->d_buf + target->offset + offset;
+			__checksum_update_object(sym, sym_offset,
+						 "reloc string", str, strlen(str));
+			continue;
+		}
+
+		if (is_sec_sym(target)) {
+			target = find_symbol_containing(reloc->sym->sec, offset);
+			if (!target)
+				continue;
+
+			offset -= target->offset;
+		}
+
+		__checksum_update_object(sym, sym_offset, "reloc name",
+					 target->demangled_name,
+					 strlen(target->demangled_name));
+		__checksum_update_object(sym, sym_offset, "reloc addend",
+					 &offset, sizeof(offset));
+	}
+}
+
+int calculate_checksums(struct objtool_file *file)
+{
+	struct instruction *insn;
+	struct symbol *sym;
+
+	if (checksum_debug_init(file))
+		return -1;
+
+	for_each_sym(file->elf, sym) {
+
+		/*
+		 * Skip cold subfunctions and aliases: they share the
+		 * parent's checksum via func_for_each_insn() which
+		 * follows func->cfunc into the cold subfunction.
+		 */
+		if (is_cold_func(sym) || is_alias_sym(sym) || !sym->len ||
+		    !sym->sec || !sym->sec->data)
+			continue;
+
+		if (is_func_sym(sym)) {
+			checksum_init(sym);
+			func_for_each_insn(file, sym, insn)
+				checksum_update_insn(file, sym, insn);
+			checksum_finish(sym);
+
+		} else if (is_object_sym(sym)) {
+			checksum_init(sym);
+			checksum_update_object(file, sym);
+			checksum_finish(sym);
+		}
+
+	}
+
+	return 0;
+}
+
+int create_sym_checksum_section(struct objtool_file *file)
+{
+	struct section *sec;
+	struct symbol *sym;
+	unsigned int idx = 0;
+	struct sym_checksum *checksum;
+	size_t entsize = sizeof(struct sym_checksum);
+
+	sec = find_section_by_name(file->elf, ".discard.sym_checksum");
+	if (sec) {
+		if (!opts.dryrun)
+			WARN("file already has .discard.sym_checksum section, skipping");
+
+		return 0;
+	}
+
+	for_each_sym(file->elf, sym)
+		if (sym->csum.checksum)
+			idx++;
+
+	sec = elf_create_section_pair(file->elf, ".discard.sym_checksum", entsize,
+				      idx, idx);
+	if (!sec)
+		return -1;
+
+	idx = 0;
+	for_each_sym(file->elf, sym) {
+		if (!sym->csum.checksum)
+			continue;
+
+		if (!elf_init_reloc(file->elf, sec->rsec, idx, idx * entsize,
+				    sym, 0, R_TEXT64))
+			return -1;
+
+		checksum = (struct sym_checksum *)sec->data->d_buf + idx;
+		checksum->addr = 0; /* reloc */
+		checksum->checksum = sym->csum.checksum;
+
+		mark_sec_changed(file->elf, sec, true);
+
+		idx++;
+	}
+
+	return 0;
+}
+
+static const char * const klp_checksum_usage[] = {
+	"objtool klp checksum [<options>] file.o",
+	NULL,
+};
+
+int cmd_klp_checksum(int argc, const char **argv)
+{
+	struct objtool_file *file;
+	int ret;
+
+	const struct option options[] = {
+		OPT_STRING(0,	"debug-checksum", &opts.debug_checksum,	"syms", "enable checksum debug output"),
+		OPT_BOOLEAN(0,	"dry-run", &opts.dryrun, "don't write modifications"),
+		OPT_END(),
+	};
+
+	argc = parse_options(argc, argv, options, klp_checksum_usage, 0);
+	if (argc != 1)
+		usage_with_options(klp_checksum_usage, options);
+
+	opts.checksum = true;
+
+	objname = argv[0];
+
+	file = objtool_open_read(objname);
+	if (!file)
+		return 1;
+
+	ret = decode_file(file);
+	if (ret)
+		goto out;
+
+	ret = calculate_checksums(file);
+	if (ret)
+		goto out;
+
+	ret = create_sym_checksum_section(file);
+
+out:
+	free_insns(file);
+
+	if (ret)
+		return ret;
+
+	if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
+		return 1;
+
+	return elf_close(file->elf);
+}