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| author | Denys Vlasenko <dvlasenk@redhat.com> | 2015-03-31 19:00:11 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-04-01 13:17:39 +0200 |
| commit | a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 (patch) | |
| tree | 7e9c124b37e7ef6f512ee9fbf7799bd9f3274a53 /arch/x86/kernel/entry_64.S | |
| parent | x86/asm: Replace "MOVQ $imm, %reg" with MOVL (diff) | |
| download | linux-a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464.tar.xz linux-a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464.zip | |
x86/asm/entry/64: Use local label to skip around sycall dispatch
Logically, we just want to jump around the following instruction
and its prologue/epilogue:
call *sys_call_table(,%rax,8)
if the syscall number is too big - we do not specifically target
the "int_ret_from_sys_call" label.
Use a local, numerical label for this jump, for more clarity.
This also makes the code smaller:
-ffffffff8187756b: 0f 87 0f 00 00 00 ja ffffffff81877580 <int_ret_from_sys_call>
+ffffffff8187756b: 77 0f ja ffffffff8187757c <int_ret_from_sys_call>
because jumps to global labels are never translated to short jump
instructions by GAS.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
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/1427821211-25099-9-git-send-email-dvlasenk@redhat.com
[ Improved the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bad285d84a9f..03c52e217680 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -331,10 +331,11 @@ tracesys_phase2: andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif - ja int_ret_from_sys_call /* RAX(%rsp) is already set */ + ja 1f /* return -ENOSYS (already in pt_regs->ax) */ movq %r10,%rcx /* fixup for C */ call *sys_call_table(,%rax,8) movq %rax,RAX(%rsp) +1: /* Use IRET because user could have changed pt_regs->foo */ /* |