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SubjectRe: [PATCH] perf annotate: fix parsing aarch64 branch instructions after objdump update
Em Thu, Aug 23, 2018 at 07:10:47PM -0500, Kim Phillips escreveu:
> Starting with binutils 2.28, aarch64 objdump adds comments to the
> disassembly output to show the alternative names of a condition code [1].
>
> It is assumed that commas in objdump comments could occur in other arches
> now or in the future, so this fix is arch-independent.
>
> The fix could have been done with arm64 specific jump__parse and
> jump__scnprintf functions, but the jump__scnprintf instruction would
> have to have its comment character be a literal, since the scnprintf
> functions cannot receive a struct arch easily.
>
> This inconvenience also applies to the generic jump__scnprintf, which
> is why we add a raw_comment pointer to struct ins_operands, so the
> __parse function assigns it to be re-used by its corresponding __scnprintf
> function.
>
> Example differences in 'perf annotate --stdio2' output on an
> aarch64 perf.data file:
>
> BEFORE: → b.cs ffff200008133d1c <unwind_frame+0x18c> // b.hs, dffff7ecc47b
> AFTER : ↓ b.cs 18c
>
> BEFORE: → b.cc ffff200008d8d9cc <get_alloc_profile+0x31c> // b.lo, b.ul, dffff727295b
> AFTER : ↓ b.cc 31c
>
> The branch target labels 18c and 31c also now appear in the output:
>
> BEFORE: add x26, x29, #0x80
> AFTER : 18c: add x26, x29, #0x80
>
> BEFORE: add x21, x21, #0x8
> AFTER : 31c: add x21, x21, #0x8
>
> The Fixes: tag below is added so stable branches will get the update; it
> doesn't necessarily mean that commit was broken at the time, rather it
> didn't withstand the aarch64 objdump update.
>
> Tested no difference in output for sample x86_64, power arch perf.data files.
>
> [1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=bb7eff5206e4795ac79c177a80fe9f4630aaf730
>
> Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> Cc: Anton Blanchard <anton@samba.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Taeung Song <treeze.taeung@gmail.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Fixes: b13bbeee5ee6 ("perf annotate: Fix branch instruction with multiple operands")
> Signed-off-by: Kim Phillips <kim.phillips@arm.com>
> ---
> tools/perf/util/annotate.c | 17 ++++++++++++++++-
> tools/perf/util/annotate.h | 1 +
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index e32ead4744bd..b83897dafbb0 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -282,7 +282,8 @@ bool ins__is_call(const struct ins *ins)
> return ins->ops == &call_ops || ins->ops == &s390_call_ops;
> }
>
> -static int jump__parse(struct arch *arch __maybe_unused, struct ins_operands *ops, struct map_symbol *ms)
> +static int jump__parse(struct arch *arch, struct ins_operands *ops,
> + struct map_symbol *ms)

Try to refrain from reflowing, what you need to do here is just to
remove that __maybe_unused.

> {
> struct map *map = ms->map;
> struct symbol *sym = ms->sym;
> @@ -291,6 +292,15 @@ static int jump__parse(struct arch *arch __maybe_unused, struct ins_operands *op
> };
> const char *c = strchr(ops->raw, ',');
> u64 start, end;
> +
> + /*
> + * Prevent from matching commas in the comment section, e.g.:
> + * ffff200008446e70: b.cs ffff2000084470f4 <generic_exec_single+0x314> // b.hs, b.nlast
> + */
> + ops->raw_comment = strchr(ops->raw, arch->objdump.comment_char);
> + if (c && ops->raw_comment && c > ops->raw_comment)
> + c = NULL;
> +
> /*
> * Examples of lines to parse for the _cpp_lex_token@@Base
> * function:
> @@ -367,6 +377,11 @@ static int jump__scnprintf(struct ins *ins, char *bf, size_t size,
> return scnprintf(bf, size, "%-6s %s", ins->name, ops->target.sym->name);
>
> c = strchr(ops->raw, ',');
> +
> + /* Prevent from matching commas in the comment section */
> + if (ops->raw_comment && c && c > ops->raw_comment)
> + c = NULL;

This is equivalent to the previous test, but why do it differently?

Since both are open coded equivalents, why not do something like:

c = validate_comma(c, ops);

That would translate to:

static inline const char *validate_comma(const char *c, ops)
{
return c > ops->raw_comment ? NULL : c;
}

Which should be a third equivalent form to check if c, having been
found, is after ops->raw_comment, if there is a raw_comment?

- Arnaldo

> +
> if (c != NULL) {
> const char *c2 = strchr(c + 1, ',');
>
> diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
> index 005a5fe8a8c6..5399ba2321bb 100644
> --- a/tools/perf/util/annotate.h
> +++ b/tools/perf/util/annotate.h
> @@ -22,6 +22,7 @@ struct ins {
>
> struct ins_operands {
> char *raw;
> + char *raw_comment;
> struct {
> char *raw;
> char *name;
> --
> 2.17.1

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