linux-kernel - [RFC 18/31] objtool: Disallow duplicate prefix symbols

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Message-ID: <569ad57b4b74af51f806e624dea25b4c912533c8.1725334260.git.jpoimboe@kernel.org>
Date: Mon,  2 Sep 2024 21:00:01 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: live-patching@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	x86@...nel.org,
	Miroslav Benes <mbenes@...e.cz>,
	Petr Mladek <pmladek@...e.com>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Song Liu <song@...nel.org>
Subject: [RFC 18/31] objtool: Disallow duplicate prefix symbols

Error out if a duplicate prefix symbol is attempted.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/check.c               | 5 ++++-
 tools/objtool/elf.c                 | 9 +++++++++
 tools/objtool/include/objtool/elf.h | 3 +++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index af945854dd72..236dc7871f01 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3866,6 +3866,7 @@ static void add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 	for (prev = prev_insn_same_sec(file, insn);
 	     prev;
 	     prev = prev_insn_same_sec(file, prev)) {
+		struct symbol *sym_pfx;
 		u64 offset;
 
 		if (prev->type != INSN_NOP)
@@ -3879,7 +3880,9 @@ static void add_prefix_symbol(struct objtool_file *file, struct symbol *func)
 		if (offset < opts.prefix)
 			continue;
 
-		elf_create_prefix_symbol(file->elf, func, opts.prefix);
+		sym_pfx = elf_create_prefix_symbol(file->elf, func, opts.prefix);
+		if (!sym_pfx)
+			ERROR("duplicate prefix symbol for %s\n", func->name);
 
 		break;
 	}
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0c95d7cdf0f5..748c170b931a 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -767,11 +767,20 @@ elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, size_t size)
 	size_t namelen = strlen(orig->name) + sizeof("__pfx_");
 	char name[SYM_NAME_LEN];
 	unsigned long offset;
+	struct symbol *sym;
 
 	snprintf(name, namelen, "__pfx_%s", orig->name);
 
+	sym = orig;
 	offset = orig->sym.st_value - size;
 
+	sec_for_each_sym_continue_reverse(orig->sec, sym) {
+		if (sym->offset < offset)
+			break;
+		if (sym->offset == offset && !strcmp(sym->name, name))
+			return NULL;
+	}
+
 	return elf_create_symbol(elf, name, orig->sec,
 				 GELF_ST_BIND(orig->sym.st_info),
 				 GELF_ST_TYPE(orig->sym.st_info),
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index e91bbe7f07bf..5ac5e7cdddee 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -399,6 +399,9 @@ static inline void set_reloc_type(struct elf *elf, struct reloc *reloc, unsigned
 #define sec_for_each_sym(sec, sym)					\
 	list_for_each_entry(sym, &sec->symbol_list, list)
 
+#define sec_for_each_sym_continue_reverse(sec, sym)			\
+	list_for_each_entry_continue_reverse(sym, &sec->symbol_list, list)
+
 #define for_each_sym(elf, sym)						\
 	for (struct section *__sec, *__fake = (struct section *)1;	\
 	     __fake; __fake = NULL)					\
-- 
2.45.2