On Thu, Oct 28, 2021 at 9:42 AM Richard Henderson <
richard.hender...@linaro.org> wrote:
> On 10/19/21 9:44 AM, Warner Losh wrote:
> > + /*
> > + * The code has to load r7 manually rather than using
> > + * "ldr r7, =SYS_return to make sure the size of the
> > + * code is correct.
> > + */
>
> This comment was applicable to the original freebsd asm source; it has no
> bearing on the
> hex instructions below
Yea, the code size will always be correct...
> > + uint32_t sigtramp_code[] = {
> > + /* 1 */ 0xE1A0000D, /* mov r0, sp */
> > + /* 2 */ 0xE2800000 + sigf_uc, /* add r0, r0, #SIGF_UC */
>
> I guess this was a bit of thumb1 source that accidentally became ABI?
> Otherwise I can't think why you wouldn't squish the mov into the add.
>
It's in our ABI. gdb and others know what the sigcode signature looks like
for sigreturn
so we can't really change it without a lot of pain... So we're kinda stuck
with very
old-school ARM code sequences for our modern armv7 port. There's likely no
reason to have the defensive call to sys_exit either, but like I said,
we're kinda
stuck with it w/o replacing it in a number of external sources... You may
see similar
issues with the aarch64 code I'll post next.
> Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
>
thanks!
Warner
> r~
>
