powerpc64/bpf: Add powerpc64 JIT support for timed may_goto

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When verifier sees a timed may_goto instruction, it emits a call to
arch_bpf_timed_may_goto() with a stack offset in BPF_REG_AX
(powerpc64 R12) and expects the refreshed count value to be returned
in the same register. The verifier doesn't save or restore any registers
before emitting this call.

arch_bpf_timed_may_goto() should act as a trampoline to call
bpf_check_timed_may_goto() with powerpc64 ELF ABI calling convention.

To support this custom calling convention, implement
arch_bpf_timed_may_goto() in assembly and make sure BPF caller saved
registers are preserved, then call bpf_check_timed_may_goto with
the powerpc64 ABI calling convention where first argument and return
value both are in R3. Finally, move the result back into BPF_REG_AX(R12)
before returning.

Also, introduce bpf_jit_emit_func_call() that computes the offset from
kernel_toc_addr(), validates that the target and emits the ADDIS/ADDI
sequence to load the function address before performing the indirect
branch via MTCTR/BCTRL. The existing code in bpf_jit_emit_func_call_rel()
is refactored to use this function.

Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260403105016.74775-1-skb99@linux.ibm.com

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This commit is contained in:

Saket Kumar Bhaskar 2026-04-03 16:20:16 +05:30 • committed by Madhavan Srinivasan

parent 2442f10c6e

commit b55b6b9ad7

4 changed files with 117 additions and 11 deletions

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4

arch/powerpc/net/Makefile

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5

arch/powerpc/net/bpf_jit_comp.c

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62

arch/powerpc/net/bpf_jit_comp64.c

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57

arch/powerpc/net/bpf_timed_may_goto.S

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