Panic in arch_hw_breakpoint_init() on Cortex-A9 (SPEAr1340)

[lkundrak@v3.sk (Lubomir Rintel)]

On Tue, 2017-04-18 at 14:03 +0100, Mark Rutland wrote:
> On Tue, Apr 18, 2017 at 12:44:28PM +0200, Lubomir Rintel wrote:
> > Hi,
> 
> Hi,
> 
> > I'm getting a crash that looks awfully lot like what ddc37832a1 [ARM:
> > 8634/1: hw_breakpoint: blacklist Scorpion CPUs] aims to fix.
> 
> Just to check, have you successfully booted a kernel on this board
> before? i.e. is this a new crash?

I've now checked, and it doesn't seem like it ever worked when
PERF_EVENTS (and in turn HAVE_HW_BREAKPOINT) is enabled. The crash look
the same up to 4.7; the previous versions also crash as soon as I
enable the options but for some reason I don't get an oops on the
console even with earlyprintk enabled (the machine reboots with panic=
argument, so there's just possibly just something wrong with the
console).

> > My hardware doesn't use a Scorpion CPU though -- it uses a Cortex-A9
> > (cpuid=0x412fc091).
> > 
> > [????0.157000] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
> > [????0.157000] Modules linked in:
> > [????0.157000] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-0.rc3.git0.2.spear2.fc26.armv7hl #1
> > [????0.157000] Hardware name: ST SPEAr1340 SoC with Flattened Device Tree
> > [????0.157000] task: ef102b80 task.stack: ef0fa000
> > [????0.157000] PC is at arch_hw_breakpoint_init+0x130/0x2a0
> > [????0.157000] LR is at arch_hw_breakpoint_init+0x7c/0x2a0
> > [????0.157000] pc : [<c0e0538c>]????lr : [<c0e052d8>]????psr: 60000013
> 
> It would be helpful to know which specific access that is.
> 
> Can you figure that out with addr2line, e.g.
> 
> ?$ addr2line -ife vmlinux c0e0538c

Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc7 #21
Hardware name: ST SPEAr1340 SoC with Flattened Device Tree
task: ef058000 task.stack: ef04c000
PC is at arch_hw_breakpoint_init+0x9c/0x2a4
LR is at arch_hw_breakpoint_init+0x84/0x2a4
pc : [<c0905504>]????lr : [<c09054ec>]????psr: 60000013

$ addr2line -ife vmlinux c0905504
core_has_os_save_restore
/home/lkundrak/spear/linux/arch/arm/kernel/hw_breakpoint.c:920
arch_hw_breakpoint_init
/home/lkundrak/spear/linux/arch/arm/kernel/hw_breakpoint.c:1082

> 
> Thanks,
> Mark