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: >>> >>>> On Tue, Dec 16, 2014 at 03:46:22PM +1100, Stephen Rothwell wrote: >>>>> Hi all, >>>>> >>>>> Please do not add any code destined for v3.20 to your linux-next >>>>> included >>>>> trees/branches until after v3.19-rc1 is released. >>>>> >>>>> Changes since 20141215: >>>>> >>>>> The infiniband tree gained a conflict against Linus' tree and a build >>>>> failure so I used the version from next-20141215. >>>>> >>>>> The userns tree gained a conflict against the vfs tree. >>>>> >>>>> The clk tree gained a build failure so I used the version from >>>>> next-20141215. >>>>> >>>>> Non-merge commits (relative to Linus' tree): 3588 >>>>> 2582 files changed, 123494 insertions(+), 135748 deletions(-) >>>>> >>>> >>>> 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
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