x86/entry/64: Fix paranoid_entry() frame pointer warning

Web:        https://git.kernel.org/torvalds/c/b3ccefaed922529e6a67de7b30af5aa38c76ace9
Commit:     b3ccefaed922529e6a67de7b30af5aa38c76ace9
Parent:     92816f571af81e9a71cc6f3dc8ce1e2fcdf7b6b8
Refname:    refs/heads/master
Author:     Josh Poimboeuf <[email protected]>
AuthorDate: Mon Feb 12 11:45:03 2018 -0600
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue Feb 13 09:04:55 2018 +0100

    x86/entry/64: Fix paranoid_entry() frame pointer warning
    
    With the following commit:
    
      f09d160992d1 ("x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros")
    
    ... one of my suggested improvements triggered a frame pointer warning:
    
      arch/x86/entry/entry_64.o: warning: objtool: paranoid_entry()+0x11: call without frame pointer save/setup
    
    The warning is correct for the build-time code, but it's actually not
    relevant at runtime because of paravirt patching.  The paravirt swapgs
    call gets replaced with either a SWAPGS instruction or NOPs at runtime.
    
    Go back to the previous behavior by removing the ELF function annotation
    for paranoid_entry() and adding an unwind hint, which effectively
    silences the warning.
    
    Reported-by: kbuild test robot <[email protected]>
    Signed-off-by: Josh Poimboeuf <[email protected]>
    Cc: Dominik Brodowski <[email protected]>
    Cc: Linus Torvalds <[email protected]>
    Cc: Peter Zijlstra <[email protected]>
    Cc: Thomas Gleixner <[email protected]>
    Cc: [email protected]
    Cc: [email protected]
    Fixes: f09d160992d1 ("x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros")
    Link: http://lkml.kernel.org/r/20180212174503.5acbymg5z6p32snu@treble
    Signed-off-by: Ingo Molnar <[email protected]>
---
 arch/x86/entry/entry_64.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index cfbf43366731..1c54204207d8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1128,6 +1128,7 @@ idtentry machine_check		do_mce			has_error_code=0	paranoid=1
  * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
  */
 ENTRY(paranoid_entry)
+	UNWIND_HINT_FUNC
 	cld
 	movl	$1, %ebx
 	movl	$MSR_GS_BASE, %ecx
@@ -1141,7 +1142,7 @@ ENTRY(paranoid_entry)
 	SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14
 
 	ret
-ENDPROC(paranoid_entry)
+END(paranoid_entry)
 
 /*
  * "Paranoid" exit path from exception stack.  This is invoked
--
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html