From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: LKML <linux-kernel@vger.kernel.org>,
"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
Andy Lutomirski <luto@kernel.org>
Subject: [PATCH 2/2] x86/entry/32: Remove leftover macros after stackprotector cleanups
Date: Mon, 5 Oct 2020 12:30:04 -0700 [thread overview]
Message-ID: <1469babd36eb342aaa5e274a73a49293fad75272.1601925251.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1601925251.git.luto@kernel.org>
Now that nonlazy-GS mode is gone, remove the macros from entry_32.S
that obfuscated^Wabstracted GS handling. The assembled output is
identical before and after this patch.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/entry_32.S | 43 ++-------------------------------------
1 file changed, 2 insertions(+), 41 deletions(-)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index ce6c3768ff65..58835e5ec866 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -53,35 +53,6 @@
#define PTI_SWITCH_MASK (1 << PAGE_SHIFT)
-/*
- * User gs save/restore
- *
- * This is leftover junk from CONFIG_X86_32_LAZY_GS. A subsequent patch
- * will remove it entirely.
- */
- /* unfortunately push/pop can't be no-op */
-.macro PUSH_GS
- pushl $0
-.endm
-.macro POP_GS pop=0
- addl $(4 + \pop), %esp
-.endm
-.macro POP_GS_EX
-.endm
-
- /* all the rest are no-op */
-.macro PTGS_TO_GS
-.endm
-.macro PTGS_TO_GS_EX
-.endm
-.macro GS_TO_REG reg
-.endm
-.macro REG_TO_PTGS reg
-.endm
-.macro SET_KERNEL_GS reg
-.endm
-
-
/* Unconditionally switch to user cr3 */
.macro SWITCH_TO_USER_CR3 scratch_reg:req
ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
@@ -234,7 +205,7 @@
.macro SAVE_ALL pt_regs_ax=%eax switch_stacks=0 skip_gs=0 unwind_espfix=0
cld
.if \skip_gs == 0
- PUSH_GS
+ pushl $0
.endif
pushl %fs
@@ -259,9 +230,6 @@
movl $(__USER_DS), %edx
movl %edx, %ds
movl %edx, %es
-.if \skip_gs == 0
- SET_KERNEL_GS %edx
-.endif
/* Switch to kernel stack if necessary */
.if \switch_stacks > 0
SWITCH_TO_KERNEL_STACK
@@ -300,7 +268,7 @@
1: popl %ds
2: popl %es
3: popl %fs
- POP_GS \pop
+ addl $(4 + \pop), %esp /* pop the unused "gs" slot */
IRET_FRAME
.pushsection .fixup, "ax"
4: movl $0, (%esp)
@@ -313,7 +281,6 @@
_ASM_EXTABLE(1b, 4b)
_ASM_EXTABLE(2b, 5b)
_ASM_EXTABLE(3b, 6b)
- POP_GS_EX
.endm
.macro RESTORE_ALL_NMI cr3_reg:req pop=0
@@ -928,7 +895,6 @@ SYM_FUNC_START(entry_SYSENTER_32)
movl PT_EIP(%esp), %edx /* pt_regs->ip */
movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */
1: mov PT_FS(%esp), %fs
- PTGS_TO_GS
popl %ebx /* pt_regs->bx */
addl $2*4, %esp /* skip pt_regs->cx and pt_regs->dx */
@@ -964,7 +930,6 @@ SYM_FUNC_START(entry_SYSENTER_32)
jmp 1b
.popsection
_ASM_EXTABLE(1b, 2b)
- PTGS_TO_GS_EX
.Lsysenter_fix_flags:
pushl $X86_EFLAGS_FIXED
@@ -1106,11 +1071,7 @@ SYM_CODE_START_LOCAL_NOALIGN(handle_exception)
SAVE_ALL switch_stacks=1 skip_gs=1 unwind_espfix=1
ENCODE_FRAME_POINTER
- /* fixup %gs */
- GS_TO_REG %ecx
movl PT_GS(%esp), %edi # get the function address
- REG_TO_PTGS %ecx
- SET_KERNEL_GS %ecx
/* fixup orig %eax */
movl PT_ORIG_EAX(%esp), %edx # get the error code
--
2.26.2
next prev parent reply other threads:[~2020-10-05 19:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 19:30 [PATCH 0/2] Clean up x86_32 stackprotector Andy Lutomirski
2020-10-05 19:30 ` [PATCH 1/2] x86/stackprotector/32: Make the canary into a regular percpu variable Andy Lutomirski
2020-10-06 2:29 ` Sean Christopherson
2020-10-06 4:51 ` Andy Lutomirski
2020-10-06 8:26 ` Peter Zijlstra
2020-10-06 17:14 ` Brian Gerst
2020-10-07 1:16 ` Andy Lutomirski
2020-10-05 19:30 ` Andy Lutomirski [this message]
2020-10-06 8:34 ` [PATCH 2/2] x86/entry/32: Remove leftover macros after stackprotector cleanups Peter Zijlstra
2020-10-05 23:10 ` [PATCH 0/2] Clean up x86_32 stackprotector Brian Gerst
2020-10-06 8:32 ` Peter Zijlstra
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