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SubjectRe: [PATCHv2] perf bpf: Fix endianness problem when loading parameters in prologue
Em Mon, Aug 14, 2017 at 01:46:44PM +0200, Thomas Richter escreveu:
> 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.
>
> Now the test runs successfully on 4.13.0-rc5:
> [root@s8360046 perf]# ./perf test bpf
> 38: BPF filter :
> 38.1: Basic BPF filtering : Ok
> 38.2: BPF pinning : Ok
> 38.3: BPF prologue generation : Ok
> 38.4: BPF relocation checker : Ok
> [root@s8360046 perf]#
>
> Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Acked-by: Wang Nan <wangnan0@huawei.com>
> Tested-by: Wang Nan <wangnan0@huawei.com>


That is strange, who is the author of the patch? Also I think Tested-by
is enough, being an even stronger form of Acked-by?

But then you also have Signed-off-by: Wang in there...

From Documentation/process/submitting-patches.rst:

---------

12) When to use Acked-by: and Cc:
---------------------------------

The Signed-off-by: tag indicates that the signer was involved in the
development of the patch, or that he/she was in the patch's delivery path.

If a person was not directly involved in the preparation or handling of a
patch but wishes to signify and record their approval of it then they can
ask to have an Acked-by: line added to the patch's changelog.

Acked-by: is often used by the maintainer of the affected code when that
maintainer neither contributed to nor forwarded the patch.

------------------

If Wang wrote the original patch and you made it better working together
with him, probably having both of you in Signed-off-by lines should be
enough?

- Arnaldo

> ---
> 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 1356220..827f914 100644
> --- a/tools/perf/util/bpf-prologue.c
> +++ b/tools/perf/util/bpf-prologue.c
> @@ -58,6 +58,46 @@ 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))
>
> @@ -258,9 +298,14 @@ 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 = (args[i].ref) ? argtype_to_ldx_size(args[i].type) : BPF_DW;
> +
> + 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);
>
> --
> 2.9.3

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