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| author | Denys Vlasenko <dvlasenk@redhat.com> | 2015-03-25 17:18:13 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-27 08:57:05 (GMT) |
| commit | 146b2b097d7a322b64b88a927fc5d870fc79a60b (patch) | |
| tree | aa889ede3648f82802043b5e5ba6913a345eb0fa /arch/x86 | |
| parent | 06ab9c1ba6a19977432b6906b0eee84804212dc6 (diff) | |
| download | linux-146b2b097d7a322b64b88a927fc5d870fc79a60b.tar.xz | |
x86/asm/entry/64: Use better label name, fix comments
A named label "ret_from_sys_call" implies that there are jumps
to this location from elsewhere, as happens with many other
labels in this file.
But this label is used only by the JMP a few insns above.
To make that obvious, use local numeric label instead.
Improve comments:
"and return regs->ax" isn't too informative. We always return
regs->ax.
The comment suggesting that it'd be cool to use rip relative
addressing for CALL is deleted. It's unclear why that would be
an improvement - we aren't striving to use position-independent
code here. PIC code here would require something like LEA
sys_call_table(%rip),reg + CALL *(reg,%rax*8)...
"iret frame is also incomplete" is no longer true, fix that too.
Also fix typo in comment.
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/1427303896-24023-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bf9afad..9988c4b 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -258,16 +258,15 @@ system_call_fastpath: andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif - ja ret_from_sys_call /* and return regs->ax */ + ja 1f /* return -ENOSYS (already in pt_regs->ax) */ movq %r10,%rcx - call *sys_call_table(,%rax,8) # XXX: rip relative + call *sys_call_table(,%rax,8) movq %rax,RAX(%rsp) +1: /* - * Syscall return path ending with SYSRET (fast path) - * Has incompletely filled pt_regs, iret frame is also incomplete. + * Syscall return path ending with SYSRET (fast path). + * Has incompletely filled pt_regs. */ -ret_from_sys_call: - LOCKDEP_SYS_EXIT DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF @@ -1407,7 +1406,7 @@ ENTRY(nmi) * NMI. */ - /* Use %rdx as out temp variable throughout */ + /* Use %rdx as our temp variable throughout */ pushq_cfi %rdx CFI_REL_OFFSET rdx, 0 |