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x86/asm/entry/64: Get rid of the FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK macros

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The FIXUP_TOP_OF_STACK macro is only necessary because we don't save %r11
to pt_regs->r11 on SYSCALL64 fast path, but we want ptrace to see it populated.

Bite the bullet, add a single additional PUSH instruction, and remove
the FIXUP_TOP_OF_STACK macro.

The RESTORE_TOP_OF_STACK macro is already a nop. Remove it too.

On SandyBridge CPU, it does not get slower:
measured 54.22 ns per getpid syscall before and after last two
changes on defconfig kernel.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
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: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1426785469-15125-4-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko 2015-03-19 18:17:48 +01:00 committed by Ingo Molnar
parent 9ed8e7d860
commit a71ffdd780
1 changed files with 2 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
arch/x86/kernel/entry_64.S
View File

@ -22,8 +22,6 @@
* - CFI macros are used to generate dwarf2 unwind information for better
* backtraces. They don't change any code.
* - ENTRY/END Define functions in the symbol table.
* - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
* frame that is otherwise undefined after a SYSCALL
* - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
* - idtentry - Define exception entry points.
*/
@ -118,23 +116,6 @@ ENDPROC(native_usergs_sysret64)
# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ
#endif
/*
* C code is not supposed to know that the iret frame is not populated.
* Every time a C function with an pt_regs argument is called from
* the SYSCALL based fast path FIXUP_TOP_OF_STACK is needed.
* RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
* manipulation.
*/
.macro FIXUP_TOP_OF_STACK tmp offset=0
/* copy flags to r11 as sysret would do */
movq EFLAGS+\offset(%rsp),\tmp
movq \tmp,R11+\offset(%rsp)
.endm
.macro RESTORE_TOP_OF_STACK tmp offset=0
/* nothing to do */
.endm
/*
* empty frame
*/
@ -265,7 +246,8 @@ GLOBAL(system_call_after_swapgs)
pushq_cfi_reg r8 /* pt_regs->r8 */
pushq_cfi_reg r9 /* pt_regs->r9 */
pushq_cfi_reg r10 /* pt_regs->r10 */
sub $(7*8),%rsp /* pt_regs->r11,bp,bx,r12-15 not saved */
pushq_cfi_reg r11 /* pt_regs->r11 */
sub $(6*8),%rsp /* pt_regs->bp,bx,r12-15 not saved */
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
jnz tracesys
@ -312,7 +294,6 @@ ret_from_sys_call:
CFI_RESTORE_STATE
int_ret_from_sys_call_fixup:
FIXUP_TOP_OF_STACK %r11
jmp int_ret_from_sys_call
/* Do syscall entry tracing */
@ -328,7 +309,6 @@ tracesys:
tracesys_phase2:
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %rdi
movq %rsp, %rdi
movq $AUDIT_ARCH_X86_64, %rsi
movq %rax,%rdx
@ -421,9 +401,7 @@ ENTRY(stub_\func)
CFI_STARTPROC
DEFAULT_FRAME 0, 8 /* offset 8: return address */
SAVE_EXTRA_REGS 8
FIXUP_TOP_OF_STACK %r11, 8
call sys_\func
RESTORE_TOP_OF_STACK %r11, 8
ret
CFI_ENDPROC
END(stub_\func)
@ -438,7 +416,6 @@ ENTRY(stub_execve)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call sys_execve
movq %rax,RAX(%rsp)
RESTORE_EXTRA_REGS
@ -451,9 +428,7 @@ ENTRY(stub_execveat)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call sys_execveat
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_EXTRA_REGS
jmp int_ret_from_sys_call
@ -469,7 +444,6 @@ ENTRY(stub_rt_sigreturn)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call sys_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
RESTORE_EXTRA_REGS
@ -483,7 +457,6 @@ ENTRY(stub_x32_rt_sigreturn)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call sys32_x32_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
RESTORE_EXTRA_REGS
@ -496,9 +469,7 @@ ENTRY(stub_x32_execve)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call compat_sys_execve
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_EXTRA_REGS
jmp int_ret_from_sys_call
@ -510,9 +481,7 @@ ENTRY(stub_x32_execveat)
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
FIXUP_TOP_OF_STACK %r11
call compat_sys_execveat
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_EXTRA_REGS
jmp int_ret_from_sys_call