Re: [leaf-user] ntpd segfaulting (copied to leaf-devel)

Hi Bob

(copying this to leaf-devel)

Sorry, I was too fast, I did not look into the i386 code but the one in 
x86_64

Am 03.05.2017 um 20:03 schrieb Robert K Coffman Jr. -Info From Data Corp.:
> Eric,
>
> IRC user ddrown confirmed the x64 patch I mentioned earlier seems to fix
> the issue on i386 as well.  I'm not really sure what to do with that
> information.  Is it possible to patch Leaf with it?
>
> https://gist.github.com/ddrown/15e943b8fe1da398320b0c0518c95554

I don't know. It looks like the RESTORE2 macro is extended with a nop 
operator in this patch. This looks like assembly code.

...

This is i386...

#define RESTORE(name, syscall) RESTORE2(name, syscall)

#ifdef __NR_rt_sigaction
/* The return code for realtime-signals.  */
# define RESTORE2(name, syscall) \
__asm__ (                                               \
         ".text\n"                                       \
         "__" #name ":\n"                                \
         "       movl    $" #syscall ", %eax\n"          \
         "       int     $0x80\n"                        \
);
RESTORE(restore_rt, __NR_rt_sigreturn)
#endif

#ifdef __NR_sigreturn
/* For the boring old signals.  */
# undef RESTORE2
# define RESTORE2(name, syscall) \
__asm__ (                                               \
         ".text\n"                                       \
         "__" #name ":\n"                                \
         "       popl    %eax\n"                         \
         "       movl    $" #syscall ", %eax\n"          \
         "       int     $0x80\n"                        \
);
RESTORE(restore, __NR_sigreturn)
#endif

and this is x86_64

#define RESTORE(name, syscall) RESTORE2(name, syscall)
#define RESTORE2(name, syscall) \
__asm__ (                                               \
         "nop\n"                                         \
         ".text\n"                                       \
         "__" #name ":\n"                                \
         "       movq    $" #syscall ", %rax\n"          \
         "       syscall\n"                              \
);

#ifdef __NR_rt_sigaction
/* The return code for realtime-signals.  */
RESTORE(restore_rt, __NR_rt_sigreturn)
#endif
#ifdef __NR_sigreturn
RESTORE(restore, __NR_sigreturn)
#endif

So in i386 the patch appears to be possible, if it is necessary I don't 
know as it looks like the nop operator could be used to make the 
assembly code align to instruction size. The nop operator is already in 
the x86_64 code.

I have not followed uClibc development. I am wondering what their 
position is on this issue.

cheers

ET

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