Hi,
> I've quickly looked up some doc on MIPS calling convention, doesn't
> seem like regs[8] is actually used for 5th input argument (the doc I
> found documented only the use of $4 through $7 for first 4 args).
> Should we drop PT_REGS_PARM5() for MIPS, while at it?
My understanding is that with o32 only 4 arguments can be passed in
registers ($4-$7). But n32 and n64 extended it to pass 8 arguments in
registers ($4-$11).
My source is "MIPS Run, Second Edition" from Dominic Sweetman table 11.2
on page 327. It is also described here:
https://en.wikipedia.org/wiki/Calling_convention#MIPS
On 7/30/20 9:55 PM, Andrii Nakryiko wrote:
On Thu, Jul 30, 2020 at 4:45 AM Jerry Cruntime <jerry.c.t@xxxxxx> wrote:
The o32, n32 and n64 calling conventions require the return
value to be stored in $v0 which maps to $2 register, i.e.,
the second register.
Fixes: c1932cd ("bpf: Add MIPS support to samples/bpf.")
---
tools/lib/bpf/bpf_tracing.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 58eceb884..ae205dcf8 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -215,7 +215,7 @@ struct pt_regs;
#define PT_REGS_PARM5(x) ((x)->regs[8])
I've quickly looked up some doc on MIPS calling convention, doesn't
seem like regs[8] is actually used for 5th input argument (the doc I
found documented only the use of $4 through $7 for first 4 args).
Should we drop PT_REGS_PARM5() for MIPS, while at it?
#define PT_REGS_RET(x) ((x)->regs[31])
#define PT_REGS_FP(x) ((x)->regs[30]) /* Works only with
CONFIG_FRAME_POINTER */
-#define PT_REGS_RC(x) ((x)->regs[1])
+#define PT_REGS_RC(x) ((x)->regs[2])
This looks good, though.
#define PT_REGS_SP(x) ((x)->regs[29])
#define PT_REGS_IP(x) ((x)->cp0_epc)
--
2.17.1
