[PATCH v6 22/25] x86/asm: annotate indirect jumps

[Peter Zijlstra]

On Wed, Oct 21, 2020 at 10:56:06AM +0200, Peter Zijlstra wrote:

> The "falls through to next function" seems to be limited to things like:
> 
>   warning: objtool: setup_vq() falls through to next function setup_vq.cold()
>   warning: objtool: e1000_xmit_frame() falls through to next function e1000_xmit_frame.cold()
> 
> So something's weird with the .cold thing on vmlinux.o runs.

Shiny, check this:

$ nm defconfig-build/vmlinux.o | grep setup_vq
00000000004d33a0 t setup_vq
00000000004d4c20 t setup_vq
000000000001edcc t setup_vq.cold
000000000001ee31 t setup_vq.cold
00000000004d3dc0 t vp_setup_vq

$ nm defconfig-build/vmlinux.o | grep e1000_xmit_frame
0000000000741490 t e1000_xmit_frame
0000000000763620 t e1000_xmit_frame
000000000002f579 t e1000_xmit_frame.cold
0000000000032b6e t e1000_xmit_frame.cold

$ nm defconfig-build/vmlinux.o | grep e1000_diag_test
000000000074c220 t e1000_diag_test
000000000075eb70 t e1000_diag_test
000000000002fc2a t e1000_diag_test.cold
0000000000030880 t e1000_diag_test.cold

I guess objtool goes sideways when there's multiple symbols with the
same name in a single object file. This obvously never happens on single
TU .o files.

Not sure what to do about that.