Merge tag 'x86_urgent_for_v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

35ce4632 · Linus Torvalds <[email protected]> · 2024-07-14 10:11:20 -07:00

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

Commit: 35ce46324556ba2dbc66a88013870d8bec8a99ef
Parents: 4d145e3f · ac8b270b

Merge commit. Changes below are compared with the first parent: 4d145e3f.

Changes

1 files changed · +10 −4

File	Status	Add	Del	Content
arch/x86/entry/entry_64_compat.S	modified	+10	−4	View file

arch/x86/entry/entry_64_compat.S

View file

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 11c9b8e..ed0a5f2 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -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