On 14.03.2019 19:30, Manuel Bouyer wrote:
> On Thu, Mar 14, 2019 at 03:14:56PM +0100, Manuel Bouyer wrote:
>> Hello,
>> I've a very strange symbol renaming issue on NetBSD 8.0/amd64:
>> syslog-ng dies with a bad syscall signal, ktrace reveals that it
>> called compat_13_sigaction13, just after properly calling __sigprocmask14.
>
>> gdb on the core dump shows:
>> Core was generated by `syslog-ng'.
>> Program terminated with signal SIGSYS, Bad system call.
>> #0 0x00007747ad46e74a in sigaction () from /usr/lib/libc.so.12
>> (gdb) up
>> #1 0x00007747b0e38f38 in g_process_perform_supervise () at lib/gprocess.c:1087
>> 1087 sigaction(SIGHUP, &sa, NULL);
>> (gdb)
>>
>> but gprocess.c properly includes signal.h, there was no warning at link time,
>> and disasembling the function confirms it:
>> 0x00007747b0e38f08 <+143>: movq $0x0,0x58(%rsp)
>> 0x00007747b0e38f11 <+152>: movq $0x0,0x60(%rsp)
>> 0x00007747b0e38f1a <+161>: movq $0x0,0x68(%rsp)
>> 0x00007747b0e38f23 <+170>: movq $0x1,0x50(%rsp)
>> 0x00007747b0e38f2c <+179>: xor %edx,%edx
>> 0x00007747b0e38f2e <+181>: mov $0x1,%edi
>> 0x00007747b0e38f33 <+186>: callq 0x7747b0e2f700 <__sigaction14@plt>
>> => 0x00007747b0e38f38 <+191>: mov $0x1,%ebp
>> 0x00007747b0e38f3d <+196>: lea 0x4c(%rsp),%r15
>> 0x00007747b0e38f42 <+201>: lea 0x41378(%rip),%r14 # 0x7747b0e7a2c1
>>
> Well, it turns out that sigaction is reimplemented by syslog-ng in
> lib/signal-handler.c. As it includes signal.h, its sigaction implementation
> is renamed to _sigaction14.
>
> This reimplementation of sigaction ends up calling the libc's one, using:
> static int (*real_sa)(int, const struct sigaction *, struct sigaction *);
>
> if (real_sa == NULL)
> {
> real_sa = dlsym(RTLD_NEXT, "sigaction");
> }
> return real_sa(signum, act, oldact);
>
>
> I could change sigaction to _sigaction14 in the dlsym here for NetBSD;
> is there a better way to do it ?
>
The proper way is to call (and detect for NetBSD): __sigaction14.
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