On Thu, Jan 22, 2015 at 4:15 PM, Chung-Lin Tang <clt...@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.t...@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 <lf...@altera.com> >>> Cc: Tobias Klauser <tklau...@distanz.ch> >>> Signed-off-by: Chung-Lin Tang <clt...@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? Regards Ley Foon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/