Messages in this thread | | | Subject | Re: [PATCH] perf bpf: Fix endianness problem when loading parameters in prologue | From | "Wangnan (F)" <> | Date | Fri, 11 Aug 2017 18:47:56 +0800 |
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Hi Thomas,
Please try this patch on your machine and give me the result.
Thank you.
On 2017/8/13 2:49, Wang Nan wrote: > Perf BPF prologue generator unconditionally fetches 8 bytes for function > parameters, which causes problem on big endian machine. Thomas gives a > detail analysis for this problem: > > http://lkml.kernel.org/r/968ebda5-abe4-8830-8d69-49f62529d151@linux.vnet.ibm.com > > This patch parses the type of each argument and converts data from > memory to expected type. > > Signed-off-by: Wang Nan <wangnan0@huawei.com> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org> > Cc: Thomas Richter <tmricht@linux.vnet.ibm.com> > Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> > Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> > Cc: Li Zefan <lizefan@huawei.com> > --- > tools/perf/tests/bpf-script-test-prologue.c | 4 ++- > tools/perf/util/bpf-prologue.c | 49 +++++++++++++++++++++++++++-- > 2 files changed, 50 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c > index b4ebc75..43f1e16 100644 > --- a/tools/perf/tests/bpf-script-test-prologue.c > +++ b/tools/perf/tests/bpf-script-test-prologue.c > @@ -26,9 +26,11 @@ static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = > (void *) 6; > > SEC("func=null_lseek file->f_mode offset orig") > -int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode, > +int bpf_func__null_lseek(void *ctx, int err, unsigned long _f_mode, > unsigned long offset, unsigned long orig) > { > + fmode_t f_mode = (fmode_t)_f_mode; > + > if (err) > return 0; > if (f_mode & FMODE_WRITE) > diff --git a/tools/perf/util/bpf-prologue.c b/tools/perf/util/bpf-prologue.c > index 6cdbee1..ce28993 100644 > --- a/tools/perf/util/bpf-prologue.c > +++ b/tools/perf/util/bpf-prologue.c > @@ -57,6 +57,46 @@ check_pos(struct bpf_insn_pos *pos) > return 0; > } > > +/* > + * Convert type string (u8/u16/u32/u64/s8/s16/s32/s64 ..., see > + * Documentation/trace/kprobetrace.txt) to size field of BPF_LDX_MEM > + * instruction (BPF_{B,H,W,DW}). > + */ > +static int > +argtype_to_ldx_size(const char *type) > +{ > + int arg_size = type ? atoi(&type[1]) : 64; > + > + switch (arg_size) { > + case 8: > + return BPF_B; > + case 16: > + return BPF_H; > + case 32: > + return BPF_W; > + case 64: > + default: > + return BPF_DW; > + } > +} > + > +static const char * > +insn_sz_to_str(int insn_sz) > +{ > + switch (insn_sz) { > + case BPF_B: > + return "BPF_B"; > + case BPF_H: > + return "BPF_H"; > + case BPF_W: > + return "BPF_W"; > + case BPF_DW: > + return "BPF_DW"; > + default: > + return "UNKNOWN"; > + } > +} > + > /* Give it a shorter name */ > #define ins(i, p) append_insn((i), (p)) > > @@ -257,9 +297,14 @@ gen_prologue_slowpath(struct bpf_insn_pos *pos, > } > > /* Final pass: read to registers */ > - for (i = 0; i < nargs; i++) > - ins(BPF_LDX_MEM(BPF_DW, BPF_PROLOGUE_START_ARG_REG + i, > + for (i = 0; i < nargs; i++) { > + int insn_sz = argtype_to_ldx_size(args[i].type); > + > + pr_debug("prologue: load arg %d, insn_sz is %s\n", > + i, insn_sz_to_str(insn_sz)); > + ins(BPF_LDX_MEM(insn_sz, BPF_PROLOGUE_START_ARG_REG + i, > BPF_REG_FP, -BPF_REG_SIZE * (i + 1)), pos); > + } > > ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_SUCCESS_CODE), pos); >
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