[PATCH v8 3/6] x86/entry_32: Add VERW just before userspace transition

Pawan Gupta
2024-02-14T02:22:09Z

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

Cc: stable@kernel.org
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.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 1b0fe4b49ea0..d3a814efbff6 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -881,6 +881,7 @@ 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.
@@ -950,6 +951,7 @@ 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
@@ -1142,6 +1144,7 @@ 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