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Message-Id: <226af8c63c5bfa361763dd041a997ee84fe926cf.1682673543.git.houwenlong.hwl@antgroup.com>
Date: Fri, 28 Apr 2023 17:51:13 +0800
From: "Hou Wenlong" <houwenlong.hwl@...group.com>
To: linux-kernel@...r.kernel.org
Cc: "Thomas Garnier" <thgarnie@...omium.org>,
"Lai Jiangshan" <jiangshan.ljs@...group.com>,
"Kees Cook" <keescook@...omium.org>,
"Hou Wenlong" <houwenlong.hwl@...group.com>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
"Dave Hansen" <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
"Masahiro Yamada" <masahiroy@...nel.org>,
"Nathan Chancellor" <nathan@...nel.org>,
"Nick Desaulniers" <ndesaulniers@...gle.com>,
"Nicolas Schier" <nicolas@...sle.eu>,
"Josh Poimboeuf" <jpoimboe@...nel.org>,
"Peter Zijlstra" <peterz@...radead.org>,
"Christophe Leroy" <christophe.leroy@...roup.eu>,
"Sathvika Vasireddy" <sv@...ux.ibm.com>,
"Thomas Weißschuh" <linux@...ssschuh.net>,
<linux-kbuild@...r.kernel.org>
Subject: [PATCH RFC 33/43] objtool: Add validation for x86 PIE support
For x86 PIE binary, only RIP-relative addressing is allowed, however,
there are still a little absolute references of R_X86_64_64 relocation
type for data section and a little absolute references of R_X86_64_32S
relocation type in pvh_start_xen() function.
Suggested-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
Cc: Thomas Garnier <thgarnie@...omium.org>
Cc: Kees Cook <keescook@...omium.org>
---
arch/x86/Kconfig | 1 +
scripts/Makefile.lib | 1 +
tools/objtool/builtin-check.c | 4 +-
tools/objtool/check.c | 82 +++++++++++++++++++++++++
tools/objtool/include/objtool/builtin.h | 1 +
5 files changed, 88 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 715f0734d065..b753a54e5ea7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2224,6 +2224,7 @@ config RELOCATABLE
config X86_PIE
def_bool n
depends on X86_64
+ select OBJTOOL if HAVE_OBJTOOL
config RANDOMIZE_BASE
bool "Randomize the address of the kernel image (KASLR)"
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 100a386fcd71..e3c804fbc421 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -270,6 +270,7 @@ objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE) += --static-call
objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION) += --uaccess
objtool-args-$(CONFIG_GCOV_KERNEL) += --no-unreachable
objtool-args-$(CONFIG_PREFIX_SYMBOLS) += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
+objtool-args-$(CONFIG_X86_PIE) += --pie
objtool-args = $(objtool-args-y) \
$(if $(delay-objtool), --link) \
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 7c175198d09f..1cf1d00464e0 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -81,6 +81,7 @@ static const struct option check_options[] = {
OPT_BOOLEAN('t', "static-call", &opts.static_call, "annotate static calls"),
OPT_BOOLEAN('u', "uaccess", &opts.uaccess, "validate uaccess rules for SMAP"),
OPT_BOOLEAN(0 , "cfi", &opts.cfi, "annotate kernel control flow integrity (kCFI) function preambles"),
+ OPT_BOOLEAN(0, "pie", &opts.pie, "validate addressing rules for PIE"),
OPT_CALLBACK_OPTARG(0, "dump", NULL, NULL, "orc", "dump metadata", parse_dump),
OPT_GROUP("Options:"),
@@ -137,7 +138,8 @@ static bool opts_valid(void)
opts.sls ||
opts.stackval ||
opts.static_call ||
- opts.uaccess) {
+ opts.uaccess ||
+ opts.pie) {
if (opts.dump_orc) {
ERROR("--dump can't be combined with other options");
return false;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5b600bbf2389..d67b80251eec 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -131,6 +131,27 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file,
for (insn = next_insn_same_sec(file, insn); insn; \
insn = next_insn_same_sec(file, insn))
+static struct instruction *find_insn_containing(struct objtool_file *file,
+ struct section *sec,
+ unsigned long offset)
+{
+ struct instruction *insn;
+
+ insn = find_insn(file, sec, 0);
+ if (!insn)
+ return NULL;
+
+ sec_for_each_insn_from(file, insn) {
+ if (insn->offset > offset)
+ return NULL;
+ if (insn->offset <= offset && (insn->offset + insn->len) > offset)
+ return insn;
+ }
+
+ return NULL;
+}
+
+
static inline struct symbol *insn_call_dest(struct instruction *insn)
{
if (insn->type == INSN_JUMP_DYNAMIC ||
@@ -4529,6 +4550,61 @@ static int validate_reachable_instructions(struct objtool_file *file)
return 0;
}
+static int is_in_pvh_code(struct instruction *insn)
+{
+ struct symbol *sym = insn->sym;
+
+ return sym && !strcmp(sym->name, "pvh_start_xen");
+}
+
+static int validate_pie(struct objtool_file *file)
+{
+ struct section *sec;
+ struct reloc *reloc;
+ struct instruction *insn;
+ int warnings = 0;
+
+ for_each_sec(file, sec) {
+ if (!sec->reloc)
+ continue;
+ if (!(sec->sh.sh_flags & SHF_ALLOC))
+ continue;
+
+ list_for_each_entry(reloc, &sec->reloc->reloc_list, list) {
+ switch (reloc->type) {
+ case R_X86_64_NONE:
+ case R_X86_64_PC32:
+ case R_X86_64_PLT32:
+ case R_X86_64_64:
+ case R_X86_64_PC64:
+ case R_X86_64_GOTPCREL:
+ break;
+ case R_X86_64_32:
+ case R_X86_64_32S:
+ insn = find_insn_containing(file, sec, reloc->offset);
+ if (!insn) {
+ WARN("can't find relocate insn near %s+0x%lx",
+ sec->name, reloc->offset);
+ } else {
+ if (is_in_pvh_code(insn))
+ break;
+ WARN("insn at %s+0x%lx is not compatible with PIE",
+ sec->name, insn->offset);
+ }
+ warnings++;
+ break;
+ default:
+ WARN("unexpected relocation type %d at %s+0x%lx",
+ reloc->type, sec->name, reloc->offset);
+ warnings++;
+ break;
+ }
+ }
+ }
+
+ return warnings;
+}
+
int check(struct objtool_file *file)
{
int ret, warnings = 0;
@@ -4673,6 +4749,12 @@ int check(struct objtool_file *file)
warnings += ret;
}
+ if (opts.pie) {
+ ret = validate_pie(file);
+ if (ret < 0)
+ return ret;
+ warnings += ret;
+ }
if (opts.stats) {
printf("nr_insns_visited: %ld\n", nr_insns_visited);
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 2a108e648b7a..1151211a5cea 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -26,6 +26,7 @@ struct opts {
bool uaccess;
int prefix;
bool cfi;
+ bool pie;
/* options: */
bool backtrace;
--
2.31.1
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