Re: [PATCH] include program header in elf files generated by perf inject

[Lieven Hey <lieven.hey@kdab.com>]

Hi,

perf is unable to open elf files generated by perf inject.

Example:
Create a file named test.dart with the following content:

void main() {
     print("Hello World");
}

and then run

perf record --call-graph dwarf -k 1 dart --generate-perf-jitdump test.dart
perf inject -j -i perf.data -o perf.data.jitted

The problem exists since 2d86612aacb78. The commit added some code that 
now requires an elf file to have a valid program header.

Cheers
Lieven

Am 13.09.22 um 11:56 schrieb James Clark:
> 
> 
> On 09/09/2022 14:47, Lieven Hey wrote:
>> Hi James,
>>
>> I looked into this again. Commit 2d86612aacb78 changed the elf loading
>> code so that a program header is now required.
>>
> 
> Can you reply-all on the original mailing list thread with this and a
> 'to' to Leo. It's probably best to continue the discussion there so Leo
> is aware.
> 
> Thanks
> 
>> Am 25.08.22 um 17:24 schrieb James Clark:
>>>
>>>
>>> On 25/08/2022 14:56, Lieven Hey wrote:
>>>> Hi James,
>>>>
>>>> I created a file named test.dart with the following content:
>>>>
>>>> void main() {
>>>>     print("Hello World");
>>>> }
>>>>
>>>> and then run
>>>>
>>>> perf record --call-graph dwarf -k 1 dart --generate-perf-jitdump
>>>> test.dart
>>>> perf inject -j -i perf.data -o perf.data.jitted
>>>>
>>>> If you now open perf.data.jitted with perf report you can see lots of
>>>> errors regarding the missing program header.
>>>
>>> Do I need a debug build of dart or some extra dependency linked into
>>> perf? I don't see any errors but I do see a load of addresses without
>>> symbols:
>>>
>>>       13.27%     0.00%  dart          ld-2.31.so          [.] dl_main
>>>               |
>>>               ---dl_main
>>>                  |
>>>                  |--11.82%--_dl_relocate_object
>>>                  |          |
>>>                  |          |--9.56%--0xffffffff85c01284
>>>                  |          |          0xffffffff8507b04c
>>>                  |          |          0xffffffff8507afe8
>>>                  |          |          0xffffffff8507aa59
>>>                  |          |          0xffffffff85253dda
>>>                  |          |          0xffffffff85253a35
>>>                  |          |          |
>>>                  |          |          |--3.81%--0xffffffff85a7831a
>>>                  |          |          |
>>>                  |          |          |--2.49%--0xffffffff85252e72
>>>
>>>
>>>
>>>>
>>>> Cheers,
>>>> Lieven
>>>>
>>>> Am 25.08.22 um 15:51 schrieb James Clark:
>>>>>
>>>>>
>>>>> On 25/08/2022 09:49, Lieven Hey wrote:
>>>>>> The missing header makes it hard for programs like elfutils to open
>>>>>> these files.
>>>>>
>>>>> Hi Lieven,
>>>>>
>>>>> Do you have an example command that demonstrates this? I'm
>>>>> interested in
>>>>> trying it out.
>>>>>
>>>>> I was also only aware of the elf files put in ~/.debug after perf
>>>>> record, but not perf inject.
>>>>>
>>>>> Thanks
>>>>> James
>>>>>
>>>>>> ---
>>>>>>     tools/perf/util/genelf.c | 14 ++++++++++++++
>>>>>>     tools/perf/util/genelf.h |  4 ++++
>>>>>>     2 files changed, 18 insertions(+)
>>>>>>
>>>>>> diff --git a/tools/perf/util/genelf.c b/tools/perf/util/genelf.c
>>>>>> index 953338b9e887..02cd9f75e3d2 100644
>>>>>> --- a/tools/perf/util/genelf.c
>>>>>> +++ b/tools/perf/util/genelf.c
>>>>>> @@ -251,6 +251,7 @@ jit_write_elf(int fd, uint64_t load_addr, const
>>>>>> char *sym,
>>>>>>         Elf_Data *d;
>>>>>>         Elf_Scn *scn;
>>>>>>         Elf_Ehdr *ehdr;
>>>>>> +    Elf_Phdr *phdr;
>>>>>>         Elf_Shdr *shdr;
>>>>>>         uint64_t eh_frame_base_offset;
>>>>>>         char *strsym = NULL;
>>>>>> @@ -285,6 +286,19 @@ jit_write_elf(int fd, uint64_t load_addr, const
>>>>>> char *sym,
>>>>>>         ehdr->e_version = EV_CURRENT;
>>>>>>         ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section
>>>>>> name */
>>>>>>     +    /*
>>>>>> +     * setup program header
>>>>>> +     */
>>>>>> +    phdr = elf_newphdr(e, 1);
>>>>>> +    phdr[0].p_type = PT_LOAD;
>>>>>> +    phdr[0].p_offset = 0;
>>>>>> +    phdr[0].p_vaddr = 0;
>>>>>> +    phdr[0].p_paddr = 0;
>>>>>> +    phdr[0].p_filesz = csize;
>>>>>> +    phdr[0].p_memsz = csize;
>>>>>> +    phdr[0].p_flags = PF_X | PF_R;
>>>>>> +    phdr[0].p_align = 8;
>>>>>> +
>>>>>>         /*
>>>>>>          * setup text section
>>>>>>          */
>>>>>> diff --git a/tools/perf/util/genelf.h b/tools/perf/util/genelf.h
>>>>>> index ae138afe6c56..b5c909546e3f 100644
>>>>>> --- a/tools/perf/util/genelf.h
>>>>>> +++ b/tools/perf/util/genelf.h
>>>>>> @@ -53,8 +53,10 @@ int jit_add_debug_info(Elf *e, uint64_t code_addr,
>>>>>> void *debug, int nr_debug_ent
>>>>>>       #if GEN_ELF_CLASS == ELFCLASS64
>>>>>>     #define elf_newehdr    elf64_newehdr
>>>>>> +#define elf_newphdr    elf64_newphdr
>>>>>>     #define elf_getshdr    elf64_getshdr
>>>>>>     #define Elf_Ehdr    Elf64_Ehdr
>>>>>> +#define Elf_Phdr    Elf64_Phdr
>>>>>>     #define Elf_Shdr    Elf64_Shdr
>>>>>>     #define Elf_Sym        Elf64_Sym
>>>>>>     #define ELF_ST_TYPE(a)    ELF64_ST_TYPE(a)
>>>>>> @@ -62,8 +64,10 @@ int jit_add_debug_info(Elf *e, uint64_t code_addr,
>>>>>> void *debug, int nr_debug_ent
>>>>>>     #define ELF_ST_VIS(a)    ELF64_ST_VISIBILITY(a)
>>>>>>     #else
>>>>>>     #define elf_newehdr    elf32_newehdr
>>>>>> +#define elf_newphdr    elf32_newphdr
>>>>>>     #define elf_getshdr    elf32_getshdr
>>>>>>     #define Elf_Ehdr    Elf32_Ehdr
>>>>>> +#define Elf_Phdr    Elf32_Phdr
>>>>>>     #define Elf_Shdr    Elf32_Shdr
>>>>>>     #define Elf_Sym        Elf32_Sym
>>>>>>     #define ELF_ST_TYPE(a)    ELF32_ST_TYPE(a)
>>>>
>>

-- 
Lieven Hey | lieven.hey@kdab.com | Software Developer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
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