On Mon, Dec 12, 2022 at 4:17 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Mon, Dec 12, 2022 at 1:11 AM Hengqi Chen <hengqi.chen@xxxxxxxxx> wrote:
> >
> > Add PT_REGS macros for LoongArch64.
> >
> > Signed-off-by: Hengqi Chen <hengqi.chen@xxxxxxxxx>
> > ---
> > tools/lib/bpf/bpf_tracing.h | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> >
> > diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
> > index 2972dc25ff72..2d7da1caa961 100644
> > --- a/tools/lib/bpf/bpf_tracing.h
> > +++ b/tools/lib/bpf/bpf_tracing.h
> > @@ -32,6 +32,9 @@
> > #elif defined(__TARGET_ARCH_arc)
> > #define bpf_target_arc
> > #define bpf_target_defined
> > +#elif defined(__TARGET_ARCH_loongarch)
> > + #define bpf_target_loongarch
> > + #define bpf_target_defined
> > #else
> >
> > /* Fall back to what the compiler says */
> > @@ -62,6 +65,9 @@
> > #elif defined(__arc__)
> > #define bpf_target_arc
> > #define bpf_target_defined
> > +#elif defined(__loongarch__) && __loongarch_grlen == 64
> > + #define bpf_target_loongarch
> > + #define bpf_target_defined
> > #endif /* no compiler target */
> >
> > #endif
> > @@ -258,6 +264,21 @@ struct pt_regs___arm64 {
> > /* arc does not select ARCH_HAS_SYSCALL_WRAPPER. */
> > #define PT_REGS_SYSCALL_REGS(ctx) ctx
> >
> > +#elif defined(bpf_target_loongarch)
> > +
> > +#define __PT_PARM1_REG regs[5]
> > +#define __PT_PARM2_REG regs[6]
> > +#define __PT_PARM3_REG regs[7]
> > +#define __PT_PARM4_REG regs[8]
> > +#define __PT_PARM5_REG regs[9]
> > +#define __PT_RET_REG regs[1]
> > +#define __PT_FP_REG regs[22]
> > +#define __PT_RC_REG regs[4]
> > +#define __PT_SP_REG regs[3]
> > +#define __PT_IP_REG csr_era
> > +/* loongarch does not select ARCH_HAS_SYSCALL_WRAPPER. */
> > +#define PT_REGS_SYSCALL_REGS(ctx) ctx
>
> Is there some online documentation explaining this architecture's
> calling conventions? It would be useful to include that as a comment
> to be able to refer back to it. On a related note, are there any
> syscall specific calling convention differences, similar to
> PT_REGS_PARM1_SYSCALL for arm64 or PT_REGS_PARM4_SYSCALL for x86-64?
>
Ok, I think [0] would be a good resource, please add a link to it in
the comment. But also it seems like PARM1-5 should map to regs[6]
through regs[10] (not regs[5] - regs[9] that you have here). And BTW,
seems like architecture supports passing more than five, PARM6 would
be regs[11]. I've been wanting to add 6th+ argument to libbpf macros'
for a while (it came up in x86-64 world for uprobes as well), so if
you have cycles, please consider helping with that as well.
Also I see orig_a0 in struct pt_regs, which seems suspiciously similar
to arm64's PT_REGS_PARM1_SYSCALL's use of orig_x0, please check about
that as well. As I said, syscalls usually have some additional quirks.
[0] https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
> > +
> > #endif
> >
> > #if defined(bpf_target_defined)
> > --
> > 2.31.1
