On Thu, Jul 30, 2020 at 1:38 PM Jerry Cruntime <jerry.c.t@xxxxxx> wrote: > > 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 > Oh, right, I should have used Wikipedia instead. :) Acked-by: Andrii Nakryiko <andriin@xxxxxx> > > 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
