| Message ID | 20210722205219.7934-5-yu-cheng.yu@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Control-flow Enforcement: Shadow Stack | expand |
On Thu, Jul 22, 2021 at 01:51:51PM -0700, Yu-cheng Yu wrote: > /* > * Some CPU features depend on higher CPUID levels, which may not always > * be available due to CPUID level capping or broken virtualization > @@ -1249,6 +1257,11 @@ static void __init cpu_parse_early_param(void) > if (cmdline_find_option_bool(boot_command_line, "noxsaves")) > setup_clear_cpu_cap(X86_FEATURE_XSAVES); > > + if (cmdline_find_option_bool(boot_command_line, "no_user_shstk")) > + setup_clear_cpu_cap(X86_FEATURE_SHSTK); > + if (cmdline_find_option_bool(boot_command_line, "no_user_ibt")) > + setup_clear_cpu_cap(X86_FEATURE_IBT); Patch 1 says: "Disabling shadow stack also disables IBT." I don't see that here.
On 8/9/2021 9:06 AM, Borislav Petkov wrote: > On Thu, Jul 22, 2021 at 01:51:51PM -0700, Yu-cheng Yu wrote: >> /* >> * Some CPU features depend on higher CPUID levels, which may not always >> * be available due to CPUID level capping or broken virtualization >> @@ -1249,6 +1257,11 @@ static void __init cpu_parse_early_param(void) >> if (cmdline_find_option_bool(boot_command_line, "noxsaves")) >> setup_clear_cpu_cap(X86_FEATURE_XSAVES); >> >> + if (cmdline_find_option_bool(boot_command_line, "no_user_shstk")) >> + setup_clear_cpu_cap(X86_FEATURE_SHSTK); >> + if (cmdline_find_option_bool(boot_command_line, "no_user_ibt")) >> + setup_clear_cpu_cap(X86_FEATURE_IBT); > > Patch 1 says: > > "Disabling shadow stack also disables IBT." > > I don't see that here. > We have X86_FEATURE_IBT dependent on X86_FEATURE_SHSTK (patch #3).
On Tue, Aug 10, 2021 at 08:39:00AM -0700, Yu, Yu-cheng wrote:
> We have X86_FEATURE_IBT dependent on X86_FEATURE_SHSTK (patch #3).
Ah, do_clear_cpu_cap() will handle the deps, missed that.
Thx.
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h index bcba3c643e63..a8df907e8017 100644 --- a/arch/x86/include/uapi/asm/processor-flags.h +++ b/arch/x86/include/uapi/asm/processor-flags.h @@ -130,6 +130,8 @@ #define X86_CR4_SMAP _BITUL(X86_CR4_SMAP_BIT) #define X86_CR4_PKE_BIT 22 /* enable Protection Keys support */ #define X86_CR4_PKE _BITUL(X86_CR4_PKE_BIT) +#define X86_CR4_CET_BIT 23 /* enable Control-flow Enforcement */ +#define X86_CR4_CET _BITUL(X86_CR4_CET_BIT) /* * x86-64 Task Priority Register, CR8 diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 64b805bd6a54..714dd97870ba 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -505,6 +505,14 @@ static __init int setup_disable_pku(char *arg) __setup("nopku", setup_disable_pku); #endif /* CONFIG_X86_64 */ +static __always_inline void setup_cet(struct cpuinfo_x86 *c) +{ + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) + return; + + cr4_set_bits(X86_CR4_CET); +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization @@ -1249,6 +1257,11 @@ static void __init cpu_parse_early_param(void) if (cmdline_find_option_bool(boot_command_line, "noxsaves")) setup_clear_cpu_cap(X86_FEATURE_XSAVES); + if (cmdline_find_option_bool(boot_command_line, "no_user_shstk")) + setup_clear_cpu_cap(X86_FEATURE_SHSTK); + if (cmdline_find_option_bool(boot_command_line, "no_user_ibt")) + setup_clear_cpu_cap(X86_FEATURE_IBT); + arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg)); if (arglen <= 0) return; @@ -1590,6 +1603,7 @@ static void identify_cpu(struct cpuinfo_x86 *c) x86_init_rdrand(c); setup_pku(c); + setup_cet(c); /* * Clear/Set all flags overridden by options, need do it
Introduce CPU setup and boot option parsing for CET features. Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Cc: Kees Cook <keescook@chromium.org> --- v25: - Remove software-defined X86_FEATURE_CET. v24: - Update #ifdef placement to reflect Kconfig changes of splitting shadow stack and ibt. arch/x86/include/uapi/asm/processor-flags.h | 2 ++ arch/x86/kernel/cpu/common.c | 14 ++++++++++++++ 2 files changed, 16 insertions(+)