Re: [PATCH] gdb: x86: fix x32 builds with inline asm

[Mike Frysinger <vapier at gentoo dot org>]

On Tuesday 08 January 2013 11:54:32 H.J. Lu wrote:
> On Tue, Jan 8, 2013 at 7:59 AM, Mike Frysinger <vapier@gentoo.org> wrote:
> > On Tuesday 08 January 2013 10:01:20 Mike Frysinger wrote:
> >> +       asm volatile ("push %0;"
> >>                       ".globl linux_ptrace_test_ret_to_nx_instr;"
> >>                       "linux_ptrace_test_ret_to_nx_instr:"
> >>                       "ret"
> >> -                     : : "r" (return_address) : "%rsp", "memory");
> >> +                     : : "r" (return_address) : "sp", "memory");
> > 
> > hrm, this works for -m32 and -m64, but doesn't actually help with -mx32. 
> > this doesn't seem to line up with my expectations.  can you suggest
> > something here H.J. Lu ?
> > 
> > $ cat test.c
> > main() { asm volatile ("push %0; ret;" : : "r"(main) : "sp", "memory"); }
> > 
> > $ gcc -m32 test.c
> >    8:   50                      push   %eax
> >    9:   c3                      ret
> > $ gcc -m64 test.c
> >    9:   50                      push   %rax
> >    a:   c3                      retq
> > 
> > $ gcc -mx32 test.c
> > test.c: Assembler messages:
> > test.c:2: Error: operand type mismatch for `push'
> 
> Can you try this?
>
> +#ifdef __x86_64__
> +                       : : "r" ((uint64_t) (uintptr_t) (return_address))

that seems to work for me, but seems wrong.  i guess while most 32/64 bit 
issues can be handled transparently, the stack still only allows 
pushing/popping of 64bit values in x32 mode.
-mike

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