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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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