Commit-ID: a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 Gitweb: http://git.kernel.org/tip/a6de5a21fb25cdbbdf3c3e9afd8481581c4f2464 Author: Denys Vlasenko <[email protected]> AuthorDate: Tue, 31 Mar 2015 19:00:11 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 1 Apr 2015 13:17:39 +0200
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 <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[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: Steven Rostedt <[email protected]> Cc: Will Drewry <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Improved the changelog. ] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/entry_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bad285d..03c52e2 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 */ /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
