[PATCH] Change MIPS linker stubs to allow for more than 2^15 symbols.
David Daney
ddaney@avtrex.com
Thu Jun 8 00:25:00 GMT 2006
Thiemo Seufer wrote:
> David Daney wrote:
>
>>As noted in this thread:
>>
>>http://sourceware.org/ml/binutils/2006-06/msg00086.html
>>
>>The mips linker would not reliably allow for more than 2^15 dynamic
>>symbols. This prevents GCC's libgcj java runtime library from being
>>correctly linked.
>>
>>The consensus was to increase the size of the linker stubs by one
>>instruction so that objects with many dynamic symbols could be supported.
>>
>>I increased the size of the stub from 16 to 20 bytes.
>
>
> It may be useful to use 24 bytes, this adheres to the ABI alignment
> rule of 2^3.
Which rule would that be? Is there such a requirement for function
entry points?
>
>
>>The new stubs
>>support up to 2^31 dynamic symbols. That should be enough for at least
>>the short term. With the patch applied I can now successfully build and
>>run libgcj from a recent GCC-4.2 snapshot on mipsel-linux.
>
>
> Hm, 2^32 symbols would nicely fit the maximum for NewABI.
I don't know mips64 well enough to know how to load an unsigned 32 bit
constant. So It had to be 2^31.
>
> [snip]
>
>>*** 631,642 ****
>> ((ABI_64_P (abfd) \
>> ? 0x03e0782d /* daddu t7,ra */ \
>> : 0x03e07821)) /* addu t7,ra */
>> #define STUB_JALR 0x0320f809 /* jalr t9,ra */
>>! #define STUB_LI16(abfd) \
>>! ((ABI_64_P (abfd) \
>>! ? 0x64180000 /* daddiu t8,zero,0 */ \
>>! : 0x24180000)) /* addiu t8,zero,0 */
>>! #define MIPS_FUNCTION_STUB_SIZE (16)
>>
>> /* The name of the dynamic interpreter. This is put in the .interp
>> section. */
>>--- 631,640 ----
>> ((ABI_64_P (abfd) \
>> ? 0x03e0782d /* daddu t7,ra */ \
>> : 0x03e07821)) /* addu t7,ra */
>>+ #define STUB_LUI 0x3c180000 /* lui t8,0 */
>> #define STUB_JALR 0x0320f809 /* jalr t9,ra */
>>! #define STUB_LI16 0x34180000 /* ori t8,zero,0 */
>>! #define MIPS_FUNCTION_STUB_SIZE (20)
>
>
> Why not the conventional expansion of lui/(d)addiu?
We are not using hi/lo relocations, so there is no requirement for this.
The calculation in the linker is easier this way.
>
> [snip]
>
>>*** 8013,8027 ****
>> MIPS_ELF_STUB_SECTION_NAME (dynobj));
>> BFD_ASSERT (s != NULL);
>>
>>- /* FIXME: Can h->dynindx be more than 64K? */
>>- if (h->dynindx & 0xffff0000)
>>- return FALSE;
>>-
>
>
> When it is 2^31, shoudn't we continue to test for overflow?
>
Probably, but I got lazy.
Please comment on my responses, and then I will generate a new patch.
David Daney.
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