Messages in this thread | | | Date | Thu, 22 Jan 2015 17:12:36 +0800 | Subject | Re: [PATCH] nios2: __kuser_sigtramp placement fix | From | Ley Foon Tan <> |
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On Thu, Jan 22, 2015 at 5:07 PM, Chung-Lin Tang <cltang@codesourcery.com> wrote: > On 2015/1/22 下午 04:43, Ley Foon Tan wrote: >> On Thu, Jan 22, 2015 at 4:15 PM, Chung-Lin Tang <cltang@codesourcery.com> wrote: >>> On 2015/1/22 03:54 PM, Ley Foon Tan wrote: >>>> On Thu, Jan 22, 2015 at 3:14 PM, Chung-Lin Tang <chunglin.tang@gmail.com> wrote: >>>>> The address of __kuser_sigtramp is wrong by one word, due to padding >>>>> __kuser_cmpxchg to fully 64 bytes. The version word at the start of the >>>>> page displaces __kuser_sigtramp to 0x1044, instead of the intended 0x1040. >>>>> >>>>> Fixed by counting the 64-byte frame from the start of the page instead >>>>> of __kuser_cmpxchg. This shortens the __kuser_cmpxchg frame to 60-bytes, >>>>> but that's likely enough. >>>>> >>>>> The zero-byte padding parts of the kuser_pad macro has been removed, due >>>>> to the .if command refusing to behave properly when there are other >>>>> .word directives in between. Probably a binutils gas bug. >>>>> >>>>> Thanks, >>>>> Chung-Lin >>>>> >>>>> Cc: Ley Foon Tan <lftan@altera.com> >>>>> Cc: Tobias Klauser <tklauser@distanz.ch> >>>>> Signed-off-by: Chung-Lin Tang <cltang@codesourcery.com> >>>>> >>>>> diff --git a/arch/nios2/kernel/entry.S b/arch/nios2/kernel/entry.S >>>>> index 0bdfd13..3224839 100644 >>>>> --- a/arch/nios2/kernel/entry.S >>>>> +++ b/arch/nios2/kernel/entry.S >>>>> @@ -492,14 +492,7 @@ ENTRY(ret_from_kernel_thread) >>>>> >>>>> /* Filling pads with undefined instructions. */ >>>>> .macro kuser_pad sym size >>>>> - .if ((. - \sym) & 3) >>>>> - .rept (4 - (. - \sym) & 3) >>>>> - .byte 0 >>>>> - .endr >>>>> - .endif >>>>> - .rept ((\size - (. - \sym)) / 4) >>>>> - .word 0xdeadbeef >>>>> - .endr >>>>> + .fill ((\size - (. - \sym)) / 4), 4, 0xdeadbeef >>>>> .endm >>>>> >>>>> .align 6 >>>>> @@ -526,7 +519,10 @@ cmpxchg_stw: >>>>> cmpxchg_ret: >>>>> ret >>>>> >>>>> - kuser_pad __kuser_cmpxchg, 64 >>>>> + /* The first 64-byte frame contains the version word, so note >>>>> + that the first padding entry is based from the start of the kuser >>>>> + page, instead of __kuser_cmpxchg. */ >>>>> + kuser_pad __kuser_helper_start, 64 >>>>> >>>>> .globl __kuser_sigtramp >>>>> __kuser_sigtramp: >>>>> -- >>>> Hi Chung-Lin >>>> >>>> I thought this is our original intention for it. >>>> >>>> First 4 bytes is the __kuser_version and each __kuser function will >>>> have 64 bytes size. >>>> >>>> 0x1000 __kuser_helper_version >>>> 0x1004 __kuser_cmpxchg >>>> 0x1044 __kuser_sigtramp >>>> >>>> Any reason you can't use __kuser_sigtramp @ 0x1044? >>> >>> Well, that's okay as well, as the main place which sets this is the >>> signal frame construction in arch/nios2/kernel/signal.c. The user space >>> is mostly oblivious to the exact location. You'll need to update it >>> that way if you prefer 0x1044, as it's currently set at 0x1040. >>> >>> I suggested 0x1040 because 64b frames aligned at 64b seemed more >>> intuitive; __kuser_cmpxchg would be a special case. >> >> I think I will change to 0x1044 in arch/nios2/kernel/signal.c. I can >> submit the fix. >> Do you need to update toolchain for this change? > > No, the toolchain is not affected by this change. Okay, will fix this.
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