linux-kernel - Re: [PATCH v6 4/7] perf annotate: Do not ignore call instruction with indirect target

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Date:   Mon, 19 Sep 2016 12:44:13 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, treeze.taeung@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, markus@...ppelsdorf.de,
        chris.ryder@....com, pawel.moll@....com, mhiramat@...nel.org,
        rmk+kernel@....linux.org.uk, jolsa@...nel.org, mpe@...erman.id.au,
        hemant@...ux.vnet.ibm.com, namhyung@...nel.org
Subject: Re: [PATCH v6 4/7] perf annotate: Do not ignore call instruction
 with indirect target

Em Fri, Aug 19, 2016 at 06:29:35PM +0530, Ravi Bangoria escreveu:
> Do not ignore call instruction with indirect target when its already
> identified as a call. This is an extension of commit e8ea1561952b
> ("perf annotate: Use raw form for register indirect call instructions")
> to generalize annotation for all instructions with indirect calls.
> 
> This is needed for certain powerpc call instructions that use address
> in a register (such as bctrl, btarl, ...).
> 
> Apart from that, when kcore is used to disassemble function, all call
> instructions were ignored. This patch will fix it as a side effect by
> not ignoring them. For example,
> 
> Before (with kcore):
>        mov    %r13,%rdi
>        callq  0xffffffff811a7e70
>      ^ jmpq   64
>        mov    %gs:0x7ef41a6e(%rip),%al
> 
> After (with kcore):
>        mov    %r13,%rdi
>      > callq  0xffffffff811a7e70
>      ^ jmpq   64
>        mov    %gs:0x7ef41a6e(%rip),%al

Ok, makes sense, but then now I have the -> and can't press enter to go
to that function, in fact for the case I'm using as a test, the
vsnprintf kernel function, I get:

       │ 56:   test   %al,%al                                                                                                                                ▒
       │     ↓ je     81                                                                                                                                     ▒
       │       lea    -0x38(%rbp),%rsi                                                                                                                       ▒
       │       mov    %r15,%rdi                                                                                                                              ▒
       │     → callq  0xffffffff993e3230 

That 0xffffffff993e3230 should've been resolved to:

[root@...et ~]# grep ffffffff993e3230 /proc/kallsyms 
ffffffff993e3230 t format_decode

Trying to investigate why it doesn't...

- Arnaldo

> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
> [Suggested about 'bctrl' instruction]
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
> ---
> Changes in v6:
>   - No change
> 
>  tools/perf/util/annotate.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index ea07588..a05423b 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -81,16 +81,12 @@ static int call__parse(struct ins_operands *ops, const char *norm_arch)
>  	return ops->target.name == NULL ? -1 : 0;
>  
>  indirect_call:
> -	tok = strchr(endptr, '(');
> -	if (tok != NULL) {
> +	tok = strchr(endptr, '*');
> +	if (tok == NULL) {
>  		ops->target.addr = 0;
>  		return 0;
>  	}
>  
> -	tok = strchr(endptr, '*');
> -	if (tok == NULL)
> -		return -1;
> -
>  	ops->target.addr = strtoull(tok + 1, NULL, 16);
>  	return 0;
>  }
> -- 
> 2.5.5