This is the mail archive of the mailing list for the glibc project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] mips/o32: fix internal_syscall5/6/7

On Thu, 17 Aug 2017, Adhemerval Zanella wrote:

> If I understood correctly Aurelien's suggestion of returning err in v1
> is not ABI strictly so it will end up calling __libc_do_syscall with a
> non-conformant ABI convention (similar to pipe implementation where requires
> assembly specific implementation for a lot of architectures to get this
> right).  Again this is something I would really to avoid.

 Using $v1 is fine, in ABI terms it's just a part of a `long long' result, 
and you can access it in plain C in the caller (shifting and masking 
individual 32-bit halves if necessary).  I've done it myself in the past 
in some bare-metal library code.

> >  If everyone but me thinks there's a clear advantage in using such a 
> > handcoded stub though, then as I previously noted please adjust the 
> > affected MIPS16 stubs to avoid the extra indirection, i.e. you can call 
> > `__libc_do_syscall' directly from MIPS16 code as you'd do from regular 
> > MIPS or microMIPS code, as the lone reason for the existence of the MIPS16 
> > stubs is the inexistence of a MIPS16 SYSCALL instruction.
> Ok, I will try to at least check it on qemu. If you have any points on how
> correctly build a mips16 glibc it could be helpful. 

 Just pass `-mips16' along with CFLAGS.  You may have to make sure your 
GCC configuration includes/supports a suitable MIPS16 mulitilib though 
(i.e. MIPS16 libgcc.a and CRT files of your chosen endianness; check with 
`-print-multi-lib' for entries with `@mips16'), to avoid interlinking 
scenarios that may not be supported.  I don't remember offhand what the 
defaults for the individual GCC configurations are, although I'm fairly 
sure at least one of `mips-mti-linux-gnu' and `mips-img-linux-gnu' 
configurations does have MIPS16 multilibs.  Let me know if you have 
troubles with that.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]