Re: [PATCH] perf annotate: fix parsing aarch64 branch instructions after objdump update

[Arnaldo Carvalho de Melo <acme@kernel.org>]

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