Re: Problems with commit 'kallsyms: add support for relative offsets in kallsyms address table' (in mmotm)
From: Ard Biesheuvel
Date: Sun Jan 24 2016 - 14:16:19 EST
> On 24 jan. 2016, at 20:01, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>
>
>
>> On 24 jan. 2016, at 19:01, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>
>> On 01/24/2016 09:20 AM, Ard Biesheuvel wrote:
>> [ ... ]
>>>>> OK, there's an additional issue in my latest version: the
>>>>> kallsyms_relative_base value itself is not relocated.
>>>>>
>>>>> If you have more time to burn on this, could you try the following on
>>>>> top? (If not, that is also fine, I will look into it myself on Monday)
>>>>>
>>>>> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
>>>>> index 5ab13394dfd9..0f43f0751d47 100644
>>>>> --- a/scripts/kallsyms.c
>>>>> +++ b/scripts/kallsyms.c
>>>>> @@ -137,8 +137,10 @@ static int read_symbol(FILE *in, struct sym_entry *s)
>>>>> sym++;
>>>>>
>>>>> /* Ignore most absolute/undefined (?) symbols. */
>>>>> - if (strcmp(sym, "_text") == 0)
>>>>> + if (strcmp(sym, "_text") == 0) {
>>>>> _text = s->addr;
>>>>> + stype = 'T';
>>>>> + }
>>>>> else if (check_symbol_range(sym, s->addr, text_ranges,
>>>>> ARRAY_SIZE(text_ranges)) == 0)
>>>>> /* nothing to do */;
>>>>> @@ -406,7 +408,7 @@ static void write_src(void)
>>>>>
>>>>> if (base_relative) {
>>>>> output_label("kallsyms_relative_base");
>>>>> - printf("\tPTR\t%#llx\n", relative_base);
>>>>> + printf("\tPTR\t_text - %#llx\n", _text - relative_base);
>>>>> printf("\n");
>>>>> }
>>>>
>>>> Does not help.
>>>
>>> For x86? Or none of them?
>>
>> I tested sparc32 and x86_64/nosmp. Doesn't help for any of them.
>> sparc32 has the following absolute symbols.
>>
>> f035a420 A _etext
>> f03d9000 A _sdata
>> f03de8c4 A jiffies
>> f03f8860 A _edata
>> f03fc000 A __init_begin
>> f041bdc8 A __init_text_end
>> f0423000 A __bss_start
>> f0423000 A __init_end
>> f044457d A __bss_stop
>> f044457d A _end
>
> Any clue why these don't get dropped? Am I missing something? Afaict A symbols get dropped unless they are whitelisted (i.e., the few ia64 ones)
>
ok, never mind. it's the symbol range check.
anyway, i should have enough info now to get this sorted
thanks,
ard
>> This results in:
>>
>> kallsyms failure: absolute symbol value 0xf035a420 out of range in relative mode
>>
>> This is with binutils 2.22. I didn't test with binutils 2.25 for sparc, or re-test mips.
>>
>>
>> Looks like I'll need to add more test cases with binutils 2.22 vs. 2.25 for various
>> architectures, as well as more SMP vs. !SMP builds.
>
> Thanks once again