linux-kernel - Re: objtool warning for wanxl_pci_init

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Date:   Fri, 6 Jan 2017 11:34:23 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: objtool warning for wanxl_pci_init_one with gcc-7

On Wed, Jan 04, 2017 at 12:19:20PM +0100, Arnd Bergmann wrote:
> Hi Josh,
> 
> I'm getting a new warning with the latest gcc-7 snapshot, I think this
> is a false positive:
> 
> drivers/net/wan/wanxl.o: warning: objtool: wanxl_pci_init_one()+0x9d2: sibling call from callable instruction with changed frame pointer
> 
> # /git/arm-soc/drivers/net/wan/wanxl.c:133:     switch((value >> STATUS_CABLE_PM_SHIFT) & 0x7) {
>         movl    %eax, %ecx      # value, _314
>         movl    %eax, %r10d     # value, _224
>         movq    (%r15), %rdi    # MEM[base: _546, offset: 0B], pretmp_490
>         shrl    $5, %ecx        #, _314
>         andl    $8, %r10d       #, _224
>         movl    %ecx, %edx      # _314, tmp377
>         andl    $7, %edx        #, tmp377
>         jmp     *(%r14,%rdx,8)  #
>         .section        .rodata
>         .align 8
>         .align 4
> .L280:
>         .quad   .L278
>         .quad   .L278
>         .quad   .L279
>         .quad   .L281
>         .quad   .L282
>         .quad   .L305
>         .quad   .L278
>         .quad   .L306
>         .text

Thanks Arnd, will take a look at it.  This reminds me that I need to
ping the gcc guys about better annotations of switch statement jump
tables.

-- 
Josh