leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

x86/asm/entry/32: Simplify the zeroing of pt_regs->r8..r11 in the int80 code path

Browse Source 
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 <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1433266510-2938-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko 2015-06-02 19:35:10 +02:00 committed by Ingo Molnar
parent 5ca6f70f38
commit 61b1e3e782
1 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/entry/ia32entry.S
View File

@ -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 */