[tip:x86/urgent] x86/asm/entry/32: Revert ' Do not use R9 in SYSCALL32' commit
From: tip-bot for Denys Vlasenko
Date: Fri Jul 24 2015 - 10:40:37 EST
Commit-ID: c0c3322e98029e752526d906d9e3a680ed213c03
Gitweb: http://git.kernel.org/tip/c0c3322e98029e752526d906d9e3a680ed213c03
Author: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
AuthorDate: Fri, 24 Jul 2015 14:16:43 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 24 Jul 2015 16:36:00 +0200
x86/asm/entry/32: Revert 'Do not use R9 in SYSCALL32' commit
This change reverts most of commit 53e9accf0f 'Do not use R9 in
SYSCALL32'. I don't yet understand how, but code in that commit
sometimes fails to preserve EBP.
See https://bugzilla.kernel.org/show_bug.cgi?id=101061
"Problems while executing 32-bit code on AMD64"
Reported-and-tested-by: Krzysztof A. Sobiecki <sobkas@xxxxxxxxx>
Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1437740203-11552-1-git-send-email-dvlasenk@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/entry/entry_64_compat.S | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index bb187a6..5a18447 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -205,7 +205,6 @@ sysexit_from_sys_call:
movl RDX(%rsp), %edx /* arg3 */
movl RSI(%rsp), %ecx /* arg4 */
movl RDI(%rsp), %r8d /* arg5 */
- movl %ebp, %r9d /* arg6 */
.endm
.macro auditsys_exit exit
@@ -236,6 +235,7 @@ sysexit_from_sys_call:
sysenter_auditsys:
auditsys_entry_common
+ movl %ebp, %r9d /* reload 6th syscall arg */
jmp sysenter_dispatch
sysexit_audit:
@@ -336,7 +336,7 @@ ENTRY(entry_SYSCALL_compat)
* 32-bit zero extended:
*/
ASM_STAC
-1: movl (%r8), %ebp
+1: movl (%r8), %r9d
_ASM_EXTABLE(1b, ia32_badarg)
ASM_CLAC
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
@@ -346,7 +346,7 @@ ENTRY(entry_SYSCALL_compat)
cstar_do_call:
/* 32-bit syscall -> 64-bit C ABI argument conversion */
movl %edi, %r8d /* arg5 */
- movl %ebp, %r9d /* arg6 */
+ /* r9 already loaded */ /* arg6 */
xchg %ecx, %esi /* rsi:arg2, rcx:arg4 */
movl %ebx, %edi /* arg1 */
movl %edx, %edx /* arg3 (zero extension) */
@@ -358,7 +358,6 @@ cstar_dispatch:
call *ia32_sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
1:
- movl RCX(%rsp), %ebp
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -392,7 +391,9 @@ sysretl_from_sys_call:
#ifdef CONFIG_AUDITSYSCALL
cstar_auditsys:
+ movl %r9d, R9(%rsp) /* register to be clobbered by call */
auditsys_entry_common
+ movl R9(%rsp), %r9d /* reload 6th syscall arg */
jmp cstar_dispatch
sysretl_audit:
@@ -404,14 +405,16 @@ cstar_tracesys:
testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jz cstar_auditsys
#endif
+ xchgl %r9d, %ebp
SAVE_EXTRA_REGS
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
movq %rax, R10(%rsp)
- movq %rax, R9(%rsp)
+ movq %r9, R9(%rsp)
movq %rax, R8(%rsp)
movq %rsp, %rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
+ movl R9(%rsp), %r9d
/* Reload arg registers from stack. (see sysenter_tracesys) */
movl RCX(%rsp), %ecx
@@ -421,6 +424,7 @@ cstar_tracesys:
movl %eax, %eax /* zero extension */
RESTORE_EXTRA_REGS
+ xchgl %ebp, %r9d
jmp cstar_do_call
END(entry_SYSCALL_compat)
--
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