Re: [PATCH v2 04/10] powerpc/traps: Use REG_FMT in show_signal_msg()

From: LEROY Christophe
Date: Mon Jul 30 2018 - 12:30:53 EST


Murilo Opsfelder Araujo <muriloo@xxxxxxxxxxxxx> a ÃcritÂ:

Hi, Christophe.

On Fri, Jul 27, 2018 at 06:40:23PM +0200, LEROY Christophe wrote:
Murilo Opsfelder Araujo <muriloo@xxxxxxxxxxxxx> a ÃcritÂ:

> Simplify the message format by using REG_FMT as the register format. This
> avoids having two different formats and avoids checking for MSR_64BIT.

Are you sure it is what we want ?

Yes.

Won't it change the behaviour for a 32 bits app running on a 64bits kernel ?

In fact, this changes how many zeroes are prefixed when displaying the registers
(%016lx vs. %08lx format). For example, 32-bits userspace, 64-bits kernel:

Indeed that's what I suspected. What is the real benefit of this change ? Why not keep the current format for 32bits userspace ? All those leading zeroes are pointless to me.


before this series:
[66475.002900] segv[4599]: unhandled signal 11 at 00000000 nip 10000420 lr 0fe61854 code 1

after this series:
[ 73.414535] segv[3759]: segfault (11) at 0000000000000000 nip 0000000010000420 lr 000000000fe61854 code 1 in segv[10000000+10000]
[ 73.414641] segv[3759]: code: 4e800421 80010014 38210010 7c0803a6 4bffff30 9421ffd0 93e1002c 7c3f0b78
[ 73.414665] segv[3759]: code: 39200000 913f001c 813f001c 39400001 <91490000> 39200000 7d234b78 397f0030

Have you spotted any other behaviour change?

Not as of today

Christophe


Cheers
Murilo