[PATCH v29 04/32] x86/cpufeatures: Introduce CPU setup and option parsing for CET
From: Yu-cheng Yu <hidden>
Date: 2021-08-20 18:19:26
Also in:
linux-api, linux-arch, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Introduce CPU setup and boot option parsing for CET features. Signed-off-by: Yu-cheng Yu <redacted> Cc: Kees Cook <redacted> --- 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(+)
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
--
2.21.0