Paul Mackerras wrote:
Mohan Kumar M writes:
@@ -714,7 +714,7 @@ _GLOBAL(enter_rtas)
std r6,PACASAVEDMSR(r13)
/* Setup our real return addr */
- LOAD_REG_ADDR(r4,.rtas_return_loc)
+ LOAD_REG_IMMEDIATE(r4,.rtas_return_loc)
If LOAD_REG_ADDR doesn't work, then how are all the TOC loads in
gcc-generated code going to work?
Hi Paul,
We have a problem only when there is a reference to a variable through got.
Following mail sent to Segher yesterday may explain it.
I was going through the output generated by objdump -D vmlinux and
readelf -h vmlinux.
<Snip objdump of vmlinux>
Disassembly of section .got:
c000000000805010 <__toc_start>:
c000000000805010: c0 00 00 00 lfs f0,0(0)
c000000000805014: 00 80 d0 10 .long 0x80d010
c000000000805018: c0 00 00 00 lfs f0,0(0)
c00000000080501c: 00 00 83 58 .long 0x8358
c000000000805020: c0 00 00 00 lfs f0,0(0)
c000000000805024: 00 85 1f e8 .long 0x851fe8
c000000000805028: c0 00 00 00 lfs f0,0(0)
c00000000080502c: 00 00 8d 84 .long 0x8d84
c000000000805030: c0 00 00 00 lfs f0,0(0)
c000000000805034: 00 85 03 38 .long 0x850338
c000000000805038: c0 00 00 00 lfs f0,0(0)
c00000000080503c: 00 85 28 b8 .long 0x8528b8
c000000000805040: c0 00 00 00 lfs f0,0(0)
c000000000805044: 00 85 28 b0 .long 0x8528b0
c000000000805048: c0 00 00 00 lfs f0,0(0)
c00000000080504c: 00 6d ef 60 .long 0x6def60
All of the variables references through @got translated into relocation
type R_PPC64_GOT16_DS entries. All these entries correspond to one of
the above entries in the .got section. But none of the entries in .got
section are relocated.
For example the instruction with relocation type R_PPC64_GOT16_DS,
c00000000000830c: e8 62 80 10 ld r3,-32752(r2)
refers to current_set variable. r2 will be pointing to
0xc00000000280d010 (relocated __toc_start + 0x8000). So the instruction
loads r3 with the content 0xc000000000851fe8 at location
0xc000000002805020, but which is not a relocated entry (0xc000000000851fe8)
But when there is a relocation type of R_PPC64_ADDR16_HI, like
c000000000008110: 64 84 00 00 oris r4,r4,0
we could easily get more info about this relocation from readelf like:
c000000000008112 000100000005 R_PPC64_ADDR16_HI c000000000000000 .text
+ 8124
So from above output we can identify that instruction at address
c000000000008112 needs to be patched with the relocation delta.
Now I have two options left:
1. Check for R_PPC64_GOT16_DS entries and check whether the contents
addressed by r2+offset is relocated or not and apply relocation if its not.
2. Change all LOAD_REG_ADDR macros to LOAD_REG_IMMEDIATE. This I have
already done.
Regards,
Mohan.
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