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.
Do the same in the second copy of the syscall table dispatch code, it has a similar JMP which skips the CALL. 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. Signed-off-by: Denys Vlasenko <[email protected]> CC: Linus Torvalds <[email protected]> CC: Steven Rostedt <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] CC: [email protected] --- Changes in v2: gave "jmp 1f" treatment to the second jump. arch/x86/kernel/entry_64.S | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bf9afad..9c8661c 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -258,16 +258,16 @@ 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 @@ -334,10 +334,11 @@ 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 */ /* -- 1.8.1.4 -- 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/
