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| author | H.J. Lu <hjl.tools@gmail.com> | 2023-12-29 08:43:52 -0800 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2024-01-01 05:22:48 -0800 |
| commit | d360dcc001cb12504cd3e8dbddee20df6bebb0f8 (patch) | |
| tree | 85424ab05ed848c3e004bb938e4e7820f9c77e1c | |
| parent | 541641a3de8d89464151bd879552755e882c832e (diff) | |
| download | glibc-d360dcc001cb12504cd3e8dbddee20df6bebb0f8.tar.gz glibc-d360dcc001cb12504cd3e8dbddee20df6bebb0f8.tar.xz glibc-d360dcc001cb12504cd3e8dbddee20df6bebb0f8.zip | |
x86/cet: Check feature_1 in TCB for active IBT and SHSTK
Initially, IBT and SHSTK are marked as active when CPU supports them and CET are enabled in glibc. They can be disabled early by tunables before relocation. Since after relocation, GLRO(dl_x86_cpu_features) becomes read-only, we can't update GLRO(dl_x86_cpu_features) to mark IBT and SHSTK as inactive. Instead, check the feature_1 field in TCB to decide if IBT and SHST are active.
| -rw-r--r-- | sysdeps/x86/bits/platform/x86.h | 8 | ||||
| -rw-r--r-- | sysdeps/x86/get-cpuid-feature-leaf.c | 11 | ||||
| -rw-r--r-- | sysdeps/x86/sys/platform/x86.h | 17 |
3 files changed, 35 insertions, 1 deletions
diff --git a/sysdeps/x86/bits/platform/x86.h b/sysdeps/x86/bits/platform/x86.h index 1e23d53ba2..1575ae53fb 100644 --- a/sysdeps/x86/bits/platform/x86.h +++ b/sysdeps/x86/bits/platform/x86.h @@ -337,3 +337,11 @@ enum x86_cpu_AVX10_YMM = x86_cpu_index_24_ecx_0_ebx + 17, x86_cpu_AVX10_ZMM = x86_cpu_index_24_ecx_0_ebx + 18, }; + +/* Bits in the feature_1 field in TCB. */ + +enum +{ + x86_feature_1_ibt = 1U << 0, + x86_feature_1_shstk = 1U << 1 +}; diff --git a/sysdeps/x86/get-cpuid-feature-leaf.c b/sysdeps/x86/get-cpuid-feature-leaf.c index 9317a6b494..f69936b31e 100644 --- a/sysdeps/x86/get-cpuid-feature-leaf.c +++ b/sysdeps/x86/get-cpuid-feature-leaf.c @@ -15,9 +15,18 @@ License along with the GNU C Library; if not, see <https://www.gnu.org/licenses/>. */ - +#include <assert.h> +#include <tcb-offsets.h> #include <ldsodefs.h> +#ifdef __x86_64__ +# ifdef __LP64__ +_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72"); +# else +_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40"); +# endif +#endif + const struct cpuid_feature * __x86_get_cpuid_feature_leaf (unsigned int leaf) { diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h index 1ea2c5fc0b..89b1b16f22 100644 --- a/sysdeps/x86/sys/platform/x86.h +++ b/sysdeps/x86/sys/platform/x86.h @@ -45,6 +45,23 @@ x86_cpu_present (unsigned int __index) static __inline__ _Bool x86_cpu_active (unsigned int __index) { + if (__index == x86_cpu_IBT || __index == x86_cpu_SHSTK) + { +#ifdef __x86_64__ + unsigned int __feature_1; +# ifdef __LP64__ + __asm__ ("mov %%fs:72, %0" : "=r" (__feature_1)); +# else + __asm__ ("mov %%fs:40, %0" : "=r" (__feature_1)); +# endif + if (__index == x86_cpu_IBT) + return __feature_1 & x86_feature_1_ibt; + else + return __feature_1 & x86_feature_1_shstk; +#else + return false; +#endif + } const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf (__index / (8 * sizeof (unsigned int) * 4)); unsigned int __reg |