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SubjectRe: [PATCH] Properly interpret indirect call in perf annotate.
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On 08/23/2018 04:12 PM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Aug 23, 2018 at 02:29:34PM +0200, Martin Liška escreveu:
>> The patch changes interpretation of:
>> callq *0x8(%rbx)
>>
>> from:
>> 0.26 │ → callq *8
>> to:
>> 0.26 │ → callq *0x8(%rbx)
>>
>> in this can an address is followed by a register, thus
>> one can't parse only address.
>
> Please mention one or two functions where such sequence appears, so that
> others can reproduce your before/after more quickly,

Sure, there's self-contained example on can compile (-O2) and test.
It's following call in test function:

test:
.LFB1:
.cfi_startproc
movq %rdi, %rax
subq $8, %rsp
.cfi_def_cfa_offset 16
movq %rsi, %rdi
movq %rdx, %rsi
call *8(%rax) <---- here
cmpl $1, %eax
adcl $-1, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
ret
.cfi_endproc

Martin

>
> - Arnaldo
>
>> Signed-off-by: Martin Liška <mliska@suse.cz>
>> ---
>> tools/perf/util/annotate.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>>
>
>> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
>> index e4268b948e0e..e32ead4744bd 100644
>> --- a/tools/perf/util/annotate.c
>> +++ b/tools/perf/util/annotate.c
>> @@ -246,8 +246,14 @@ static int call__parse(struct arch *arch, struct ins_operands *ops, struct map_s
>>
>> indirect_call:
>> tok = strchr(endptr, '*');
>> - if (tok != NULL)
>> - ops->target.addr = strtoull(tok + 1, NULL, 16);
>> + if (tok != NULL) {
>> + endptr++;
>> +
>> + /* Indirect call can use a non-rip register and offset: callq *0x8(%rbx).
>> + * Do not parse such instruction. */
>> + if (strstr(endptr, "(%r") == NULL)
>> + ops->target.addr = strtoull(endptr, NULL, 16);
>> + }
>> goto find_target;
>> }
>>
>>
>
typedef int (*htab_eq) (const void *, const void *);

static int eq (const void *a, const void *b)
{
return a - b;
}

struct htab
{
/* Current size (in entries) of the hash table */
int size;

/* Pointer to comparison function. */
htab_eq eq_f;

/* Table itself. */
void **entries;

/* Current number of elements including also deleted elements */
int n_elements;

/* Current number of deleted elements in the table */
int n_deleted;

/* The following member is used for debugging. Its value is number
of all calls of `htab_find_slot' for the hash table. */
unsigned int searches;

/* The following member is used for debugging. Its value is number
of collisions fixed for time of work with the hash table. */
unsigned int collisions;

unsigned int max_size;

/* This is non-zero if we are allowed to return NULL for function calls
that allocate memory. */
int return_allocation_failure;
};

int
__attribute__ ((noinline))
test(struct htab *t, int *a, int *b)
{
int r = t->eq_f (a, b);
if (r)
return r - 1;

return 0;
}

struct htab mytable;
int r;

int main(int argc, char **argv)
{
mytable.eq_f = &eq;
for (unsigned i = 0; i < 100000000; i++)
r += test (&mytable, &argc, &argc);

return 0;
}
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