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Message-Id: <20180110010328.22163-9-andi@firstfloor.org>
Date: Tue, 9 Jan 2018 17:03:28 -0800
From: Andi Kleen <andi@...stfloor.org>
To: tglx@...utronix.de
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
torvalds@...ux-foundation.org, dwmw@...zon.co.uk, pjt@...gle.com,
luto@...nel.org, peterz@...radead.org, thomas.lendacky@....com,
tim.c.chen@...ux.intel.com, gregkh@...ux-foundation.org,
dave.hansen@...el.com, jikos@...nel.org,
Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v1 8/8] x86/entry/clearregs: Clear registers for 32bit kernel
From: Andi Kleen <ak@...ux.intel.com>
On a 32bit kernel clearing registers is much simpler than
on 64bit. The arguments for syscalls are initially passed
to a C function through the stack, so there's no need
to figure out how many arguments to clear.
So we always clear all registers (except frame pointer) for
all entry points.
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
arch/x86/entry/entry_32.S | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index d2ef7f32905b..aee1085534ac 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -221,6 +221,18 @@
POP_GS_EX
.endm
+.macro CLEAR_ALL_REGS
+#ifdef CONFIG_FRAME_POINTER
+ xorl %ebp, %ebp
+#endif
+ xorl %eax, %eax
+ xorl %ebx, %ebx
+ xorl %ecx, %ecx
+ xorl %edx, %edx
+ xorl %edi, %edi
+ xorl %esi, %esi
+.endm
+
/*
* %eax: prev task
* %edx: next task
@@ -428,6 +440,7 @@ ENTRY(entry_SYSENTER_32)
pushl $0 /* pt_regs->ip = 0 (placeholder) */
pushl %eax /* pt_regs->orig_ax */
SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
+ CLEAR_ALL_REGS
/*
* SYSENTER doesn't filter flags, so we need to clear NT, AC
@@ -539,6 +552,7 @@ ENTRY(entry_INT80_32)
ASM_CLAC
pushl %eax /* pt_regs->orig_ax */
SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */
+ CLEAR_ALL_REGS
/*
* User mode is traced as though IRQs are on, and the interrupt gate
@@ -673,6 +687,7 @@ common_interrupt:
ASM_CLAC
addl $-0x80, (%esp) /* Adjust vector into the [-256, -1] range */
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
TRACE_IRQS_OFF
movl %esp, %eax
@@ -685,6 +700,7 @@ ENTRY(name) \
ASM_CLAC; \
pushl $~(nr); \
SAVE_ALL; \
+ CLEAR_ALL_REGS; \
ENCODE_FRAME_POINTER; \
TRACE_IRQS_OFF \
movl %esp, %eax; \
@@ -812,6 +828,7 @@ END(spurious_interrupt_bug)
ENTRY(xen_hypervisor_callback)
pushl $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
TRACE_IRQS_OFF
@@ -867,6 +884,7 @@ ENTRY(xen_failsafe_callback)
jmp iret_exc
5: pushl $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
jmp ret_from_exception
@@ -921,6 +939,7 @@ common_exception:
pushl %edx
pushl %ecx
pushl %ebx
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
cld
movl $(__KERNEL_PERCPU), %ecx
@@ -954,6 +973,7 @@ ENTRY(debug)
ASM_CLAC
pushl $-1 # mark this as an int
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
xorl %edx, %edx # error code 0
movl %esp, %eax # pt_regs pointer
@@ -998,6 +1018,7 @@ ENTRY(nmi)
pushl %eax # pt_regs->orig_ax
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
xorl %edx, %edx # zero error code
movl %esp, %eax # pt_regs pointer
@@ -1038,6 +1059,7 @@ ENTRY(nmi)
.endr
pushl %eax
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
FIXUP_ESPFIX_STACK # %eax == %esp
xorl %edx, %edx # zero error code
@@ -1052,6 +1074,7 @@ ENTRY(int3)
ASM_CLAC
pushl $-1 # mark this as an int
SAVE_ALL
+ CLEAR_ALL_REGS
ENCODE_FRAME_POINTER
TRACE_IRQS_OFF
xorl %edx, %edx # zero error code
--
2.14.3
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