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Message-ID: <ed05aca9028fa80d9f48ee88ebb80dc90c6a4194.1746821544.git.jpoimboe@kernel.org>
Date: Fri, 9 May 2025 13:17:20 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
Petr Mladek <pmladek@...e.com>,
Miroslav Benes <mbenes@...e.cz>,
Joe Lawrence <joe.lawrence@...hat.com>,
live-patching@...r.kernel.org,
Song Liu <song@...nel.org>,
laokz <laokz@...mail.com>,
Jiri Kosina <jikos@...nel.org>,
Marcos Paulo de Souza <mpdesouza@...e.com>,
Weinan Liu <wnliu@...gle.com>,
Fazla Mehrab <a.mehrab@...edance.com>,
Chen Zhongjin <chenzhongjin@...wei.com>,
Puranjay Mohan <puranjay@...nel.org>
Subject: [PATCH v2 56/62] objtool: Add base objtool support for livepatch modules
In preparation for klp-build, enable "classic" objtool to work on
livepatch modules:
- Avoid duplicate symbol/section warnings for prefix symbols and the
.static_call_sites and __mcount_loc sections which may have already
been extracted by klp diff.
- Add __klp_funcs to the IBT function pointer section whitelist.
- Prevent KLP symbols from getting incorrectly classified as cold
subfunctions.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
tools/objtool/check.c | 44 +++++++++++++++++++++----
tools/objtool/elf.c | 4 ++-
tools/objtool/include/objtool/elf.h | 1 +
tools/objtool/include/objtool/objtool.h | 2 +-
4 files changed, 43 insertions(+), 8 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index bc9bc37efa55..5bd1b8d000bd 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3,6 +3,7 @@
* Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@...hat.com>
*/
+#define _GNU_SOURCE /* memmem() */
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
@@ -627,6 +628,20 @@ static int init_pv_ops(struct objtool_file *file)
return 0;
}
+static bool is_livepatch_module(struct objtool_file *file)
+{
+ struct section *sec;
+
+ if (!opts.module)
+ return false;
+
+ sec = find_section_by_name(file->elf, ".modinfo");
+ if (!sec)
+ return false;
+
+ return memmem(sec->data->d_buf, sec_size(sec), "\0livepatch=Y", 12);
+}
+
static int create_static_call_sections(struct objtool_file *file)
{
struct static_call_site *site;
@@ -638,7 +653,12 @@ static int create_static_call_sections(struct objtool_file *file)
sec = find_section_by_name(file->elf, ".static_call_sites");
if (sec) {
- if (!opts.dryrun)
+ /*
+ * Livepatch modules may have already extracted the static call
+ * site entries to take advantage of vmlinux static call
+ * privileges.
+ */
+ if (!!opts.dryrun || !file->klp)
WARN("file already has .static_call_sites section, skipping");
return 0;
@@ -684,7 +704,7 @@ static int create_static_call_sections(struct objtool_file *file)
key_sym = find_symbol_by_name(file->elf, tmp);
if (!key_sym) {
- if (!opts.module) {
+ if (!opts.module || file->klp) {
ERROR("static_call: can't find static_call_key symbol: %s", tmp);
return -1;
}
@@ -911,7 +931,11 @@ static int create_mcount_loc_sections(struct objtool_file *file)
sec = find_section_by_name(file->elf, "__mcount_loc");
if (sec) {
- if (!opts.dryrun)
+ /*
+ * Livepatch modules have already extracted their __mcount_loc
+ * entries to cover the !CONFIG_FTRACE_MCOUNT_USE_OBJTOOL case.
+ */
+ if (!opts.dryrun && !file->klp)
WARN("file already has __mcount_loc section, skipping");
return 0;
@@ -2612,6 +2636,8 @@ static int decode_sections(struct objtool_file *file)
{
int ret;
+ file->klp = is_livepatch_module(file);
+
mark_rodata(file);
ret = init_pv_ops(file);
@@ -4285,8 +4311,13 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
if (offset < opts.prefix)
continue;
+ /*
+ * Ignore attempts to make duplicate symbols in livepatch
+ * modules. They've already extracted the prefix symbols
+ * except for the newly compiled init.c.
+ */
sym_pfx = elf_create_prefix_symbol(file->elf, func, opts.prefix);
- if (!sym_pfx) {
+ if (!sym_pfx && !file->klp) {
WARN("duplicate prefix symbol for %s\n", func->name);
return -1;
}
@@ -4621,6 +4652,7 @@ static int validate_ibt(struct objtool_file *file)
!strncmp(sec->name, ".debug", 6) ||
!strcmp(sec->name, ".altinstructions") ||
!strcmp(sec->name, ".ibt_endbr_seal") ||
+ !strcmp(sec->name, ".kcfi_traps") ||
!strcmp(sec->name, ".orc_unwind_ip") ||
!strcmp(sec->name, ".retpoline_sites") ||
!strcmp(sec->name, ".smp_locks") ||
@@ -4630,12 +4662,12 @@ static int validate_ibt(struct objtool_file *file)
!strcmp(sec->name, "__bug_table") ||
!strcmp(sec->name, "__ex_table") ||
!strcmp(sec->name, "__jump_table") ||
+ !strcmp(sec->name, "__klp_funcs") ||
!strcmp(sec->name, "__mcount_loc") ||
- !strcmp(sec->name, ".kcfi_traps") ||
!strcmp(sec->name, ".llvm.call-graph-profile") ||
!strcmp(sec->name, ".llvm_bb_addr_map") ||
!strcmp(sec->name, "__tracepoints") ||
- strstr(sec->name, "__patchable_function_entries"))
+ !strcmp(sec->name, "__patchable_function_entries"))
continue;
for_each_reloc(sec->rsec, reloc)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index de1d8554d979..ae1c852ff8d8 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -496,8 +496,10 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym)
(strstarts(sym->name, "__pfx") || strstarts(sym->name, "__cfi_")))
sym->prefix = 1;
+ if (strstarts(sym->name, ".klp.sym"))
+ sym->klp = 1;
- if (is_func_sym(sym) && strstr(sym->name, ".cold"))
+ if (!sym->klp && is_func_sym(sym) && strstr(sym->name, ".cold"))
sym->cold = 1;
sym->pfunc = sym->cfunc = sym;
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 1bf9c0a1112d..adfe508f96f5 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -84,6 +84,7 @@ struct symbol {
u8 debug_checksum : 1;
u8 changed : 1;
u8 included : 1;
+ u8 klp : 1;
struct list_head pv_target;
struct reloc *relocs;
struct section *group_sec;
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 37e9fe4492d6..731965a742e9 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -30,7 +30,7 @@ struct objtool_file {
struct list_head mcount_loc_list;
struct list_head endbr_list;
struct list_head call_list;
- bool ignore_unreachables, hints, rodata;
+ bool ignore_unreachables, hints, rodata, klp;
unsigned int nr_endbr;
unsigned int nr_endbr_int;
--
2.49.0
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