> powerpc/bpf: Move out dummy_tramp_addr after Long branch stub
>
> Move the long branch address space to the bottom of the long
> branch stub. This allows uninterrupted disassembly until the
> last 8 bytes. Exclude these last bytes from the overall
> program length to prevent failure in assembly generation.
> Also, align dummy_tramp_addr field with 8-byte boundary.
>
> Following is disassembler output for test program with moved down
> dummy_tramp_addr field:
> .....
> .....
> pc:68 left:44 a6 03 08 7c : mtlr 0
> pc:72 left:40 bc ff ff 4b : b .-68
> pc:76 left:36 a6 02 68 7d : mflr 11
> pc:80 left:32 05 00 9f 42 : bcl 20, 31, .+4
> pc:84 left:28 a6 02 88 7d : mflr 12
> pc:88 left:24 14 00 8c e9 : ld 12, 20(12)
> pc:92 left:20 a6 03 89 7d : mtctr 12
> pc:96 left:16 a6 03 68 7d : mtlr 11
> pc:100 left:12 20 04 80 4e : bctr
> pc:104 left:8 c0 34 1d 00 :
>
> Failure log:
> Can't disasm instruction at offset 104: c0 34 1d 00 00 00 00 c0
> Disassembly logic can truncate at 104, ignoring last 8 bytes.
>
> Update the dummy_tramp_addr field offset calculation from the end
> of the program to reflect its new location, for bpf_arch_text_poke()
> to update the actual trampoline's address in this field.
>
> All BPF trampoline selftests continue to pass with this patch applied.
>
> Signed-off-by: Abhishek Dubey <[email protected]>
This looks like a bug fix for the bpf trampoline implementation on
powerpc64. Should this include a Fixes tag?
The bug was introduced in commit d243b62b7bd3 which added support for bpf
trampolines on powerpc64. That commit placed the dummy_tramp_addr field at
the beginning of the long branch stub, causing the disassembly failures and
incorrect offset calculations that this patch fixes.
Suggested:
Fixes: d243b62b7bd3 ("powerpc64/bpf: Add support for bpf trampolines")
---
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See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/26121409898
