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SubjectRe: [PATCH v3 4/4] objtool: orc_gen: Move orc_entry out of instruction structure
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On 7/30/20 11:03 AM, peterz@infradead.org wrote:
> On Thu, Jul 30, 2020 at 10:41:43AM +0100, Julien Thierry wrote:
>> One orc_entry is associated with each instruction in the object file,
>> but having the orc_entry contained by the instruction structure forces
>> architectures not implementing the orc subcommands to provide a dummy
>> definition of the orc_entry.
>>
>> Avoid that by having orc_entries in a separate list, part of the
>> objtool_file.
>>
>
>> diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
>> index 66fd56c33303..00f1efd05653 100644
>> --- a/tools/objtool/orc_gen.c
>> +++ b/tools/objtool/orc_gen.c
>> @@ -9,18 +9,33 @@
>> #include "check.h"
>> #include "warn.h"
>>
>> +struct orc_data {
>> + struct list_head list;
>> + struct instruction *insn;
>> + struct orc_entry orc;
>> +};
>> +
>> int create_orc(struct objtool_file *file)
>> {
>> struct instruction *insn;
>>
>> for_each_insn(file, insn) {
>> - struct orc_entry *orc = &insn->orc;
>> struct cfi_reg *cfa = &insn->cfi.cfa;
>> struct cfi_reg *bp = &insn->cfi.regs[CFI_BP];
>> + struct orc_entry *orc;
>> + struct orc_data *od;
>>
>> if (!insn->sec->text)
>> continue;
>>
>> + od = calloc(1, sizeof(*od));
>> + if (!od)
>> + return -1;
>> + od->insn = insn;
>> + list_add_tail(&od->list, &file->orc_data_list);
>> +
>> + orc = &od->orc;
>> +
>> orc->end = insn->cfi.end;
>>
>> if (cfa->base == CFI_UNDEFINED) {
>
> This will dramatically increase the amount of allocation calls, what, if
> anything, does this do for the performance of objtool?
>

I guess I forgot about the usecase of running objtool on vmlinux...

On a kernel build for x86_64 defconfig, the difference in time seems to
be withing the noise.

But I agree the proposed code is not ideal and on the other we've tried
avoiding #ifdef in the code. Ideally I'd have an empty orc_entry
definition when SUBCMD_ORC is not implemented.

Would you have a suggested approach to do that?

Thanks,

--
Julien Thierry

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