[v5,09/14] tools/nolibc: add missing my_syscall6() for mips
Commit Message
It is able to pass the 6th argument like the 5th argument via the stack
for mips, let's add a new my_syscall6() now, see [1] for details:
The mips/o32 system call convention passes arguments 5 through 8 on
the user stack.
Both mmap() and pselect6() require my_syscall6().
[1]: https://man7.org/linux/man-pages/man2/syscall.2.html
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
---
tools/include/nolibc/arch-mips.h | 25 +++++++++++++++++++++++++
tools/include/nolibc/nolibc.h | 9 ++++-----
2 files changed, 29 insertions(+), 5 deletions(-)
Comments
Hi Zhangjin,
On Wed, Jun 28, 2023 at 09:37:29PM +0800, Zhangjin Wu wrote:
> It is able to pass the 6th argument like the 5th argument via the stack
> for mips, let's add a new my_syscall6() now, see [1] for details:
>
> The mips/o32 system call convention passes arguments 5 through 8 on
> the user stack.
>
> Both mmap() and pselect6() require my_syscall6().
Very interesting, I didn't manage to make it work previously. Did you
test it to confirm that it works ? I guess so but since you didn't
mention, I preferred to ask.
Thanks!
Willy
Hi, Willy
> Hi Zhangjin,
>
> On Wed, Jun 28, 2023 at 09:37:29PM +0800, Zhangjin Wu wrote:
> > It is able to pass the 6th argument like the 5th argument via the stack
> > for mips, let's add a new my_syscall6() now, see [1] for details:
> >
> > The mips/o32 system call convention passes arguments 5 through 8 on
> > the user stack.
> >
> > Both mmap() and pselect6() require my_syscall6().
>
> Very interesting, I didn't manage to make it work previously. Did you
> test it to confirm that it works ? I guess so but since you didn't
> mention, I preferred to ask.
>
Yes, I'm curious too ;-)
we did add the mmap test cases and run it for mips, as Thomas
suggested, we pass a none-zero pa_offset to mmap() to make sure the 6th
argument is used.
I just re-tested it for mips and printed something like this:
44 mmap_bad = <0xffffffff> EINVAL [OK]
45 munmap_bad = -1 EINVAL [OK]
46 mmap_munmap_good
pa_offset: 8192
length: 1
file_size: 12287
= 0 [OK]
47 open_tty = 3 [OK]
48 open_blah = -1 ENOENT [OK]
And I also checked the mips support of musl, it evan provide a
__syscall7, so, it should be ok ;-)
The only difference is, musl provide a different clobber list for
'__mips_isa_rev >= 6', I didn't look into the details yet:
https://elixir.bootlin.com/musl/latest/source/arch/mips/syscall_arch.h
Best regards,
Zhangjin
> Thanks!
> Willy
@@ -176,6 +176,31 @@ struct sys_stat_struct {
_arg4 ? -_num : _num; \
})
+#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
+({ \
+ register long _num __asm__ ("v0") = (num); \
+ register long _arg1 __asm__ ("a0") = (long)(arg1); \
+ register long _arg2 __asm__ ("a1") = (long)(arg2); \
+ register long _arg3 __asm__ ("a2") = (long)(arg3); \
+ register long _arg4 __asm__ ("a3") = (long)(arg4); \
+ register long _arg5 = (long)(arg5); \
+ register long _arg6 = (long)(arg6); \
+ \
+ __asm__ volatile ( \
+ "addiu $sp, $sp, -32\n" \
+ "sw %7, 16($sp)\n" \
+ "sw %8, 20($sp)\n" \
+ "syscall\n " \
+ "addiu $sp, $sp, 32\n" \
+ : "=r" (_num), "=r"(_arg4) \
+ : "0"(_num), \
+ "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+ "r"(_arg6) \
+ : SYSCALL_CLOBBERLIST \
+ ); \
+ _arg4 ? -_num : _num; \
+})
+
char **environ __attribute__((weak));
const unsigned long *_auxv __attribute__((weak));
@@ -13,11 +13,10 @@
* Syscalls are split into 3 levels:
* - The lower level is the arch-specific syscall() definition, consisting in
* assembly code in compound expressions. These are called my_syscall0() to
- * my_syscall6() depending on the number of arguments. The MIPS
- * implementation is limited to 5 arguments. All input arguments are cast
- * to a long stored in a register. These expressions always return the
- * syscall's return value as a signed long value which is often either a
- * pointer or the negated errno value.
+ * my_syscall6() depending on the number of arguments. All input arguments
+ * are castto a long stored in a register. These expressions always return
+ * the syscall's return value as a signed long value which is often either
+ * a pointer or the negated errno value.
*
* - The second level is mostly architecture-independent. It is made of
* static functions called sys_<name>() which rely on my_syscallN()