[PATCH 5.10.y v2 04/11] x86/entry_32: Add VERW just before userspace transition

Pawan Gupta
2024-03-12T22:40:45Z

commit a0e2dab44d22b913b4c228c8b52b2a104434b0b3 upstream.

As done for entry_64, add support for executing VERW late in exit to
user path for 32-bit mode.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-3-a6216d83edb7%40linux.intel.com
---
arch/x86/entry/entry_32.S | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 70bd81b6c612..840e4f01005c 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -997,6 +997,7 @@ SYM_FUNC_START(entry_SYSENTER_32)
BUG_IF_WRONG_CR3 no_user_check=1
popfl
popl %eax
+ CLEAR_CPU_BUFFERS

/*
* Return back to the vDSO, which will pop ecx and edx.
@@ -1069,6 +1070,7 @@ restore_all_switch_stack:

/* Restore user state */
RESTORE_REGS pop=4 # skip orig_eax/error_code
+ CLEAR_CPU_BUFFERS
.Lirq_return:
/*
* ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization
@@ -1267,6 +1269,7 @@ SYM_CODE_START(asm_exc_nmi)

/* Not on SYSENTER stack. */
call exc_nmi
+ CLEAR_CPU_BUFFERS
jmp .Lnmi_return

.Lnmi_from_sysenter_stack:

--
2.34.1