32-bit syscall entry points do not save complete pt_regs struct -
they leave some fields uninitialized. However, they must be careful
to not leak uninitialized data in pt_regs->r8..r11 to ptrace users.
CLEAR_RREGS macro is used to zero these fields out when needed.
However, on int80 code path this zeroing is unconditional. This patch
simplifies it by storing zeroes there right away, when pt_regs
is constructed on stack. This uses shrter instructions:
text data bss dec hex filename
1423 0 0 1423 58f ia32entry.o.before
1407 0 0 1407 57f ia32entry.o
Compile-tested.
Signed-off-by: Denys Vlasenko <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: Ingo Molnar <[email protected]>
CC: Borislav Petkov <[email protected]>
CC: "H. Peter Anvin" <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Frederic Weisbecker <[email protected]>
CC: Alexei Starovoitov <[email protected]>
CC: Will Drewry <[email protected]>
CC: Kees Cook <[email protected]>
CC: [email protected]
CC: [email protected]
---
arch/x86/ia32/ia32entry.S | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 2be23c7..2801cbe 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -421,6 +421,10 @@ ia32_badarg:
movq $-EFAULT,%rax
jmp ia32_sysret
+ia32_ret_from_sys_call:
+ CLEAR_RREGS
+ jmp int_ret_from_sys_call
+
/*
* Emulated IA32 system calls via int 0x80.
*
@@ -462,8 +466,12 @@ ENTRY(ia32_syscall)
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq $-ENOSYS /* pt_regs->ax */
+ pushq $0 /* pt_regs->r8 */
+ pushq $0 /* pt_regs->r9 */
+ pushq $0 /* pt_regs->r10 */
+ pushq $0 /* pt_regs->r11 */
cld
- sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
+ sub $(6*8),%rsp /* pt_regs->bp,bx,r12-15 not saved */
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -481,13 +489,10 @@ ia32_do_call:
ia32_sysret:
movq %rax,RAX(%rsp)
1:
-ia32_ret_from_sys_call:
- CLEAR_RREGS
jmp int_ret_from_sys_call
ia32_tracesys:
SAVE_EXTRA_REGS
- CLEAR_RREGS
movq %rsp,%rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
LOAD_ARGS32 /* reload args from stack in case ptrace changed it */
--
1.8.1.4
Commit-ID: 61b1e3e782d6784b714c0d80de529e0737d0e79c
Gitweb: http://git.kernel.org/tip/61b1e3e782d6784b714c0d80de529e0737d0e79c
Author: Denys Vlasenko <[email protected]>
AuthorDate: Tue, 2 Jun 2015 19:35:10 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Fri, 5 Jun 2015 13:22:21 +0200
x86/asm/entry/32: Simplify the zeroing of pt_regs->r8..r11 in the int80 code path
32-bit syscall entry points do not save the complete pt_regs struct,
they leave some fields uninitialized. However, they must be
careful to not leak uninitialized data in pt_regs->r8..r11 to
ptrace users.
CLEAR_RREGS macro is used to zero these fields out when needed.
However, in the int80 code path this zeroing is unconditional.
This patch simplifies it by storing zeroes there right away,
when pt_regs is constructed on stack.
This uses shorter instructions:
text data bss dec hex filename
1423 0 0 1423 58f ia32entry.o.before
1407 0 0 1407 57f ia32entry.o
Compile-tested.
Signed-off-by: Denys Vlasenko <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Drewry <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/entry/ia32entry.S | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/ia32entry.S b/arch/x86/entry/ia32entry.S
index f167674..f00a409 100644
--- a/arch/x86/entry/ia32entry.S
+++ b/arch/x86/entry/ia32entry.S
@@ -421,6 +421,10 @@ ia32_badarg:
movq $-EFAULT,%rax
jmp ia32_sysret
+ia32_ret_from_sys_call:
+ CLEAR_RREGS
+ jmp int_ret_from_sys_call
+
/*
* Emulated IA32 system calls via int 0x80.
*
@@ -462,8 +466,12 @@ ENTRY(ia32_syscall)
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq $-ENOSYS /* pt_regs->ax */
+ pushq $0 /* pt_regs->r8 */
+ pushq $0 /* pt_regs->r9 */
+ pushq $0 /* pt_regs->r10 */
+ pushq $0 /* pt_regs->r11 */
cld
- sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
+ sub $(6*8),%rsp /* pt_regs->bp,bx,r12-15 not saved */
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -481,13 +489,10 @@ ia32_do_call:
ia32_sysret:
movq %rax,RAX(%rsp)
1:
-ia32_ret_from_sys_call:
- CLEAR_RREGS
jmp int_ret_from_sys_call
ia32_tracesys:
SAVE_EXTRA_REGS
- CLEAR_RREGS
movq %rsp,%rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
LOAD_ARGS32 /* reload args from stack in case ptrace changed it */