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235b2fe772
Implement stack argument passing for BPF-to-BPF and kfunc calls with more than 5 parameters on arm64, following the AAPCS64 calling convention. BPF R1-R5 already map to x0-x4. With BPF_REG_0 moved to x8 by the previous commit, x5-x7 are free for arguments 6-8. Arguments 9-12 spill onto the stack at [SP+0], [SP+8], ... and the callee reads them from [FP+16], [FP+24], ... (above the saved FP/LR pair). BPF convention uses fixed offsets from BPF_REG_PARAMS (r11): off=-8 is always arg 6, off=-16 arg 7, etc. The verifier invalidates all outgoing stack arg slots after each call, so the compiler must re-store before every call. This means x5-x7 don't need to be saved on stack. Signed-off-by: Puranjay Mohan <puranjay@kernel.org> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20260513045158.2402494-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>