[Skiboot] [PATCH] Fix early backtraces

[Stewart Smith]

Ryan Grimm <grimm at linux.vnet.ibm.com> writes:

> If we fail an assert() before we add a mem region, such as missing chip-id in a
> dt xscom node, we don't get a backtrace:
>
> [836883,0] Assert fail: core/device.c:870:id != 0xffffffff
> [848859,0] Aborting!
> CPU 0000 Backtrace:
>
> This patch adjusts the top_of_ram value compared to the fp stack frame to
> assume one stack early on so we get a backtrace:
>
> [440546,0] Assert fail: core/device.c:822:id != 0xffffffff
> [452522,0] Aborting!
> CPU 0000 Backtrace:
>  S: 0000000031c03b70 R: 00000000300135d0   .backtrace+0x24
>  S: 0000000031c03bf0 R: 0000000030017f38   ._abort+0x4c
>  S: 0000000031c03c70 R: 0000000030017fb4   .assert_fail+0x34
>  S: 0000000031c03cf0 R: 0000000030021830   .dt_get_chip_id+0x24
>  S: 0000000031c03d60 R: 00000000300143cc   .init_chips+0x23c
>  S: 0000000031c03e30 R: 0000000030013ab8   .main_cpu_entry+0x110
>  S: 0000000031c03f00 R: 000000003000254c   boot_entry+0x19c
>
> Signed-off-by: Ryan Grimm <grimm at linux.vnet.ibm.com>

Looks good, thanks!

Applied to master as of fbf1bb9

-- 
Stewart Smith
OPAL Architect, IBM.