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. Chung-Lin -- 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/
