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x86: Properly set usable CET feature bits [BZ #26625]

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commit 94cd37ebb2
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Sep 16 05:27:32 2020 -0700

    x86: Use HAS_CPU_FEATURE with IBT and SHSTK [BZ #26625]

broke

GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK

since it can no longer disable IBT nor SHSTK.  Handle IBT and SHSTK with:

1. Revert commit 94cd37ebb2.
2. Clears the usable CET feature bits if kernel doesn't support CET.
3. Add GLIBC_TUNABLES tests without dlopen.
4. Add tests to verify that CPU_FEATURE_USABLE on IBT and SHSTK matches
_get_ssp.
5. Update GLIBC_TUNABLES tests with dlopen to verify that CET is disabled
with GLIBC_TUNABLES.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
H.J. Lu
2021-01-26 20:48:45 -08:00
parent 6032ae6514
commit 04dff6fc0d
10 changed files with 120 additions and 13 deletions
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4
sysdeps/x86/dl-cet.c
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@ -77,11 +77,11 @@ dl_cet_check (struct link_map *m, const char *program)
GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
*/
enable_ibt &= (HAS_CPU_FEATURE (IBT)
enable_ibt &= (CPU_FEATURE_USABLE (IBT)
&& (enable_ibt_type == cet_always_on
|| (m->l_x86_feature_1_and
& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0));
enable_shstk &= (HAS_CPU_FEATURE (SHSTK)
enable_shstk &= (CPU_FEATURE_USABLE (SHSTK)
&& (enable_shstk_type == cet_always_on
|| (m->l_x86_feature_1_and
& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0));