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Date: Fri, 28 Apr 2023 10:28:19 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Hou Wenlong <houwenlong.hwl@...group.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Thomas Garnier <thgarnie@...omium.org>,
Lai Jiangshan <jiangshan.ljs@...group.com>,
Kees Cook <keescook@...omium.org>,
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" <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>,
Sathvika Vasireddy <sv@...ux.ibm.com>,
Thomas Weißschuh <linux@...ssschuh.net>,
"linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH RFC 33/43] objtool: Add validation for x86 PIE support
Le 28/04/2023 à 11:51, Hou Wenlong a écrit :
> [Vous ne recevez pas souvent de courriers de houwenlong.hwl@...group.com. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>
> 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:
That looks very specific to X86, should it go at another place ?
If it can work for any architecture, can you add generic macros, just
like commit c1449735211d ("objtool: Use macros to define arch specific
reloc types") then commit c984aef8c832 ("objtool/powerpc: Add --mcount
specific implementation") ?
> + 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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