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- Make sure TF is cleared before calling other functions (BHI mitigation in

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this case) in the SYSENTER compat handler, as otherwise it will warn about
   being in single-step mode
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Merge tag 'x86_urgent_for_v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:

 - Make sure TF is cleared before calling other functions (BHI
   mitigation in this case) in the SYSENTER compat handler, as
   otherwise it will warn about being in single-step mode

* tag 'x86_urgent_for_v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/bhi: Avoid warning in #DB handler due to BHI mitigation
This commit is contained in:
Linus Torvalds 2024-07-14 10:11:20 -07:00
commit 35ce463245
1 changed files with 10 additions and 4 deletions
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14
arch/x86/entry/entry_64_compat.S
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@ -89,10 +89,6 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
cld
IBRS_ENTER
UNTRAIN_RET
CLEAR_BRANCH_HISTORY
/*
* SYSENTER doesn't filter flags, so we need to clear NT and AC
* ourselves. To save a few cycles, we can check whether
@ -116,6 +112,16 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
jnz .Lsysenter_fix_flags
.Lsysenter_flags_fixed:
/*
* CPU bugs mitigations mechanisms can call other functions. They
* should be invoked after making sure TF is cleared because
* single-step is ignored only for instructions inside the
* entry_SYSENTER_compat function.
*/
IBRS_ENTER
UNTRAIN_RET
CLEAR_BRANCH_HISTORY
movq %rsp, %rdi
call do_SYSENTER_32
jmp sysret32_from_system_call