x86/entry: Make sync_regs() invocation a tail call

No point in having a call there. Spare the call/ret overhead.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111146.539578813@infradead.org

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5c578a7dfcd79def8cbb934f175fd81a09cad3fb..b24b84b3425fb50232688972384de46bb1c33d5b 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1062,11 +1062,8 @@ SYM_CODE_START_LOCAL(error_entry)
        UNTRAIN_RET
 
        leaq    8(%rsp), %rdi                   /* arg0 = pt_regs pointer */
-.Lerror_entry_from_usermode_after_swapgs:
-
        /* Put us onto the real thread stack. */
-       call    sync_regs
-       RET
+       jmp     sync_regs
 
        /*
         * There are two places in the kernel that can potentially fault with
@@ -1124,7 +1121,7 @@ SYM_CODE_START_LOCAL(error_entry)
        leaq    8(%rsp), %rdi                   /* arg0 = pt_regs pointer */
        call    fixup_bad_iret
        mov     %rax, %rdi
-       jmp     .Lerror_entry_from_usermode_after_swapgs
+       jmp     sync_regs
 SYM_CODE_END(error_entry)
 
 SYM_CODE_START_LOCAL(error_return)