Re: [PATCH v2] bfd/elfnn-aarch64.c: Fix calculation of DT_RELASZ

[Will Newton <will dot newton at linaro dot org>]

On 20 March 2014 17:57, Jiong Wang <jiong.wang@arm.com> wrote:
> On 20/03/14 15:46, Will Newton wrote:
>>
>> The current code subtracts the size of the output section containing
>> relplt from RELASZ. In some cases this will be the same output
>> section
>
>
> Hi Will,
>
>   I guess you can only trigger this "same output section" issue when using
> "ld-aarch64/aarch64.ld", right?

Yes, it requires a custom linker script. The problem arose building
OSv for aarch64:

https://github.com/cloudius-systems/osv

You could say the linker script is incorrect not to lay out the
dynamic reloc sections explicitly but it seems counter intuitive
behaviour to set RELASZ to zero when it clearly isn't.

A number of ports base the size on the size of the output sections:

lm32
m32r
nds32
sh-32
xtensa
s390-64
x86_64

But the rest use the size of input sections.

>
> --
> Jiong
>
>
>> as the dynamic relocs causing a value of zero to be output.
>> Calculating the size from input sections seems to make more sense.
>>
>> bfd/ChangeLog:
>>
>> 2014-03-20  Will Newton  <will.newton@linaro.org>
>>
>>          * elfnn-aarch64.c (elfNN_aarch64_finish_dynamic_sections):
>>          Set value of DT_PLTRELSZ and DT_RELASZ based on the size
>>          of input sections rather than output sections.
>>
>> ld/testsuite/ChangeLog:
>>
>> 2014-03-20  Will Newton  <will.newton@linaro.org>
>>
>>          * ld-aarch64/aarch64-elf.exp: Add relasz dump test.
>>          * ld-aarch64/relasz.d: New file.
>>          * ld-aarch64/relasz.s: Likewise.
>> ---
>>   bfd/elfnn-aarch64.c                     |  4 ++--
>>   ld/testsuite/ld-aarch64/aarch64-elf.exp |  2 ++
>>   ld/testsuite/ld-aarch64/relasz.d        | 18 ++++++++++++++++++
>>   ld/testsuite/ld-aarch64/relasz.s        |  9 +++++++++
>>   4 files changed, 31 insertions(+), 2 deletions(-)
>>   create mode 100644 ld/testsuite/ld-aarch64/relasz.d
>>   create mode 100644 ld/testsuite/ld-aarch64/relasz.s
>>
>> Changes in v2:
>>   - Add testcase
>>
>> diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
>> index c2adcc9..638938d 100644
>> --- a/bfd/elfnn-aarch64.c
>> +++ b/bfd/elfnn-aarch64.c
>> @@ -6993,7 +6993,7 @@ elfNN_aarch64_finish_dynamic_sections (bfd
>> *output_bfd,
>>               break;
>>             case DT_PLTRELSZ:
>> -             s = htab->root.srelplt->output_section;
>> +             s = htab->root.srelplt;
>>               dyn.d_un.d_val = s->size;
>>               break;
>>   @@ -7007,7 +7007,7 @@ elfNN_aarch64_finish_dynamic_sections (bfd
>> *output_bfd,
>>                  about changing the DT_RELA entry.  */
>>               if (htab->root.srelplt != NULL)
>>                 {
>> -                 s = htab->root.srelplt->output_section;
>> +                 s = htab->root.srelplt;
>>                   dyn.d_un.d_val -= s->size;
>>                 }
>>               break;
>> diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp
>> b/ld/testsuite/ld-aarch64/aarch64-elf.exp
>> index 32cf73a..845ea20 100644
>> --- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
>> +++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
>> @@ -157,3 +157,5 @@ run_dump_test "ifunc-19b"
>>   run_dump_test "ifunc-20"
>>   run_dump_test "ifunc-21"
>>   run_dump_test "ifunc-22"
>> +
>> +run_dump_test "relasz"
>> diff --git a/ld/testsuite/ld-aarch64/relasz.d
>> b/ld/testsuite/ld-aarch64/relasz.d
>> new file mode 100644
>> index 0000000..5cc5595
>> --- /dev/null
>> +++ b/ld/testsuite/ld-aarch64/relasz.d
>> @@ -0,0 +1,18 @@
>> +#source: relasz.s
>> +#ld: -shared -Taarch64.ld
>> +#readelf: -d
>> +# Check that the RELASZ section has the correct size even if we are
>> +# using a non-default linker script that merges .rela.dyn and .rela.plt
>> +# in the output.
>> +
>> +Dynamic section at offset 0x[0-9a-f]+ contains 9 entries:
>> +  Tag        Type                         Name/Value
>> + 0x0000000000000004 \(HASH\)               0x[0-9a-f]+
>> + 0x0000000000000005 \(STRTAB\)             0x[0-9a-f]+
>> + 0x0000000000000006 \(SYMTAB\)             0x[0-9a-f]+
>> + 0x000000000000000a \(STRSZ\)              [0-9]+ \(bytes\)
>> + 0x000000000000000b \(SYMENT\)             [0-9]+ \(bytes\)
>> + 0x0000000000000007 \(RELA\)               0x[0-9a-f]+
>> + 0x0000000000000008 \(RELASZ\)             24 \(bytes\)
>> + 0x0000000000000009 \(RELAENT\)            24 \(bytes\)
>> + 0x0000000000000000 \(NULL\)               0x0
>> diff --git a/ld/testsuite/ld-aarch64/relasz.s
>> b/ld/testsuite/ld-aarch64/relasz.s
>> new file mode 100644
>> index 0000000..8c7f891
>> --- /dev/null
>> +++ b/ld/testsuite/ld-aarch64/relasz.s
>> @@ -0,0 +1,9 @@
>> +       .text
>> +       .global func
>> +       .type   func, %function
>> +func:
>> +       adrp    x0, :got:foo
>> +       ldr     x0, [x0, #:got_lo12:foo]
>> +       ldr     w0, [x0]
>> +       ret
>> +       .size   func, .-func
>
>
> --
> Jiong
>
>



-- 
Will Newton
Toolchain Working Group, Linaro