90 lines
2.8 KiB
Diff
90 lines
2.8 KiB
Diff
From 7b3c43e6b089eb7efefdbb32b99da6b1ab469151 Mon Sep 17 00:00:00 2001
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From: "H.J. Lu" <hjl.tools@gmail.com>
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Date: Tue, 11 Apr 2023 14:03:43 -0700
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Subject: [PATCH v2 15/15] x86/cet: Check feature_1 in TCB for active IBT and
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SHSTK
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Initially, IBT and SHSTK are marked as active when CPU supports them
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and CET are enabled in glibc. They can be disabled early by tunables
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before relocation. Since after relocation, GLRO(dl_x86_cpu_features)
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becomes read-only, we can't update GLRO(dl_x86_cpu_features) to mark
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IBT and SHSTK as inactive. Instead, check the feature_1 field in TCB
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to decide if IBT and SHST are active.
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---
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sysdeps/x86/bits/platform/x86.h | 8 ++++++++
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sysdeps/x86/get-cpuid-feature-leaf.c | 11 ++++++++++-
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sysdeps/x86/sys/platform/x86.h | 17 +++++++++++++++++
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3 files changed, 35 insertions(+), 1 deletion(-)
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diff --git a/sysdeps/x86/bits/platform/x86.h b/sysdeps/x86/bits/platform/x86.h
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index 6555f9b91d..c9b6ee1766 100644
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--- a/sysdeps/x86/bits/platform/x86.h
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+++ b/sysdeps/x86/bits/platform/x86.h
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@@ -326,3 +326,11 @@ enum
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x86_cpu_PTWRITE = x86_cpu_index_14_ecx_0_ebx + 4
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};
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+
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+/* Bits in the feature_1 field in TCB. */
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+
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+enum
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+{
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+ x86_feature_1_ibt = 1U << 0,
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+ x86_feature_1_shstk = 1U << 1
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+};
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diff --git a/sysdeps/x86/get-cpuid-feature-leaf.c b/sysdeps/x86/get-cpuid-feature-leaf.c
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index 9317a6b494..f69936b31e 100644
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--- a/sysdeps/x86/get-cpuid-feature-leaf.c
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+++ b/sysdeps/x86/get-cpuid-feature-leaf.c
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@@ -15,9 +15,18 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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-
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+#include <assert.h>
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+#include <tcb-offsets.h>
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#include <ldsodefs.h>
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+#ifdef __x86_64__
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+# ifdef __LP64__
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+_Static_assert (FEATURE_1_OFFSET == 72, "FEATURE_1_OFFSET != 72");
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+# else
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+_Static_assert (FEATURE_1_OFFSET == 40, "FEATURE_1_OFFSET != 40");
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+# endif
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+#endif
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+
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const struct cpuid_feature *
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__x86_get_cpuid_feature_leaf (unsigned int leaf)
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{
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diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h
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index 1ea2c5fc0b..89b1b16f22 100644
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--- a/sysdeps/x86/sys/platform/x86.h
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+++ b/sysdeps/x86/sys/platform/x86.h
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@@ -45,6 +45,23 @@ x86_cpu_present (unsigned int __index)
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static __inline__ _Bool
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x86_cpu_active (unsigned int __index)
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{
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+ if (__index == x86_cpu_IBT || __index == x86_cpu_SHSTK)
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+ {
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+#ifdef __x86_64__
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+ unsigned int __feature_1;
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+# ifdef __LP64__
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+ __asm__ ("mov %%fs:72, %0" : "=r" (__feature_1));
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+# else
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+ __asm__ ("mov %%fs:40, %0" : "=r" (__feature_1));
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+# endif
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+ if (__index == x86_cpu_IBT)
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+ return __feature_1 & x86_feature_1_ibt;
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+ else
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+ return __feature_1 & x86_feature_1_shstk;
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+#else
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+ return false;
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+#endif
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+ }
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const struct cpuid_feature *__ptr = __x86_get_cpuid_feature_leaf
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(__index / (8 * sizeof (unsigned int) * 4));
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unsigned int __reg
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--
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2.40.1
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