[PATCH v2 1/8] ARM: replace PROCINFO embedded branch with relative offset

[Russell King - ARM Linux]

On Sun, Apr 19, 2015 at 06:59:45PM +0200, Joachim Eastwood wrote:
> Hi Ard,
> On 13 March 2015 at 13:07, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
> > This patch replaces the 'branch to setup()' instructions embedded
> > in the PROCINFO structs with the offset to that setup function
> > relative to the base of the struct. This preserves the position
> > independent nature of that field, but uses a data item rather
> > than an instruction.
> >
> > This is mainly done to prevent linker failures on large kernels,
> > where the setup function is out of reach for the branch.
> 
> This commit (bf35706f3d09 in Linus master) breaks booting on ARMv7-M.
> 
> When I try to boot Linus master now on my NXP LPC4357 (Cortex-M4) dev
> kit I get the following message from u-boot.
> ## Booting kernel from Legacy Image at 29000000 ...
> Image Name: Linux
> Image Type: ARM Linux Kernel Image (uncompressed)
> Data Size: 1412318 Bytes = 1.3 MB
> Load Address: 28008000
> Entry Point: 28008001
> Verifying Checksum ... OK
> Loading Kernel Image ... OK
> OK
> 
> Starting kernel ...
> 
> UNHANDLED EXCEPTION: HARD FAULT
> R0 = ffffffff R1 = 00001038
> R2 = 281d8711 R3 = 00000000
> R12 = 2822092c LR = 28008023
> PC = 2822092e PSR = 21000000
> 
> Reverting bf35706f3d09 (plus fixing a small conflict) makes Linus
> master boot again.
> 
> I am using the following compiler:
> gcc version 4.9.2 20140904 (prerelease) (crosstool-NG
> linaro-1.13.1-4.9-2014.09 - Linaro GCC 4.9-2014.09
> 
> The ARMv7-M machine that I am using is not upstream yet, but you can
> find the patch set on the mailing list.

Interesting... it works here with stock gcc 4.9.2.  Maybe it's a bug in
the Linaro gcc?

Could you mail me (privately) your vmlinux file (the one in the root
directory) for analysis please?

Thanks.

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