Hi Andrew, On Tue, 16 Dec 2014 10:45:49 +0000 James Hogan <james.hogan@xxxxxxxxxx> wrote: > > On 16/12/14 09:42, James Hogan wrote: > > On 16/12/14 06:55, Guenter Roeck wrote: > >> On 12/15/2014 10:44 PM, Andrew Morton wrote: > >>> On Mon, 15 Dec 2014 22:35:49 -0800 Guenter Roeck <linux@xxxxxxxxxxxx> > >>> wrote: > >>> > >>>> My metag buildbot test fails with this kernel. > >>> > >>> Thanks. What are the error messages? > >>> > >> Nothing. It just hangs until killed. > >> > >> qemu log: > >> char device redirected to /dev/pts/5 > >> Unable to load ROM! > >> qemu: terminating on signal 15 from pid 17843 > >> > >> http://server.roeck-us.net:8010/builders/qemu-metag-next/builds/60/steps/qemubuildcommand/logs/stdio > > > > Thanks a lot Guenter for report and bisection. I've confirmed on real > > hardware too. I'll try debugging it. > > The fmt in the first printk gets corrupted and causes a memory fault > because the stack isn't 64-bit aligned. The args get saved with a 64-bit > store (but unaligned access checking isn't turned on yet so this > silently does the wrong thing), and then read as 1 with a 32-bit load. > > Enabling unaligned access checking from boot makes it fail at > metag_start_kernel, immediately after stack pointer is set to > init_thread_union + THREAD_INFO_SIZE. Basically the restart_block was > the only thing keeping the struct thread_info as a whole 64-bit aligned > on Meta. > > The patch below fixes it. Please can it be squashed into commit "all > arches, signal: move restart_block to struct task_struct". > > Thanks > James > > From 3ec117304ebde939fd181129227de28c068e7fa2 Mon Sep 17 00:00:00 2001 > From: James Hogan <james.hogan@xxxxxxxxxx> > Date: Tue, 16 Dec 2014 10:15:33 +0000 > Subject: [PATCH] metag: Align thread_info::supervisor_stack > > Commit a82be12232dc ("all arches, signal: move restart_block to struct > task_struct") removed restart_block from struct thread_info which was > the only thing keeping supervisor_stack and the struct as a whole 64-bit > aligned. This resulted in the initial stack pointer not being 64-bit > aligned, so when arguments are saved to the stack with a 64-bit SETL > instruction the values are corrupted resulting in a pretty early > unserviced memory fault in printk. > > This is fixed by explicitly aligning supervisor_stack to 8 bytes. > > Fixes: a82be12232dc ("all arches, signal: move restart_block to struct task_struct") > Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx> > Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > arch/metag/include/asm/thread_info.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/metag/include/asm/thread_info.h b/arch/metag/include/asm/thread_info.h > index ff4332435d15..afb3ca4776d1 100644 > --- a/arch/metag/include/asm/thread_info.h > +++ b/arch/metag/include/asm/thread_info.h > @@ -36,7 +36,7 @@ struct thread_info { > > mm_segment_t addr_limit; /* thread address space */ > > - u8 supervisor_stack[0]; > + u8 supervisor_stack[0] __aligned(8); > }; > > #else /* !__ASSEMBLY__ */ > -- > 2.0.4 So should I just dump that patch into my copy of your tree? (it seems harmless and lets people get onto other stuff) -- Cheers, Stephen Rothwell sfr@xxxxxxxxxxxxxxxx
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