Re: [musl] [PATCH 02/14] time64: Don't make aliases to nonexistent syscalls

["Stefan O'Rear" <sorear@fastmail.com>]

On Thu, Sep 3, 2020, at 11:56 AM, Rich Felker wrote:
> On Thu, Sep 03, 2020 at 07:22:57AM -0400, Stefan O'Rear wrote:
> > riscv32 and future architectures lack the _time32 variants entirely, so
> > don't try to use their numbers.
> > ---
> >  src/internal/syscall.h | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/src/internal/syscall.h b/src/internal/syscall.h
> > index d5f294d4..66fc4e5c 100644
> > --- a/src/internal/syscall.h
> > +++ b/src/internal/syscall.h
> > @@ -201,6 +201,7 @@ static inline long __alt_socketcall(int sys, int sock, int cp, long a, long b, l
> >  #define SYS_sendfile SYS_sendfile64
> >  #endif
> >  
> > +#ifdef SYS_timer_settime32
> >  #ifndef SYS_timer_settime
> >  #define SYS_timer_settime SYS_timer_settime32
> >  #endif
> > @@ -240,6 +241,7 @@ static inline long __alt_socketcall(int sys, int sock, int cp, long a, long b, l
> >  #ifndef SYS_settimeofday
> >  #define SYS_settimeofday SYS_settimeofday_time32
> >  #endif
> > +#endif
> 
> The existing expectation internally in musl is that archs that lack
> legacy time32 syscalls have both the unadorned and _time64 macros
> defined to the same value. The public headers don't have to be like
> that but the internal ones do. See arch/x32/syscall_arch.h which does
> it but in the opposite direction. This logic is all tested for x32 and
> a big part of the point of that was preparing for rv32 and future
> 32-bit archs.
> 
> I'm actually missing how this patch worked as-written, since for
> example timer_settime.c unconditionally assumes SYS_timer_settime is
> defined, and if it's defined to anything other than the same value as
> the time64 version, it will use the value as a fallback.

src/internal/syscall.h has two groups of conditional definitions of unadorned
syscall numbers, the first of which sets undefined syscalls to the _time32
version, the second of which sets to the _time64 version.  So for instance I
see no way for the #define SYS_clock_gettime SYS_clock_gettime64
(https://git.musl-libc.org/cgit/musl/tree/src/internal/syscall.h#n250) to execute.

-s