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Yonghong Song
324c3ca6ee
Add x86_64 JIT support for BPF functions and kfuncs with more than 5 arguments. The extra arguments are passed through a stack area addressed by register r11 (BPF_REG_PARAMS) in BPF bytecode, which the JIT translates to native code. The JIT follows the x86-64 calling convention for both BPF-to-BPF and kfunc calls: - Arg 6 is passed in the R9 register - Args 7+ are passed on the stack Incoming arg 6 (BPF r11+8) is translated to a MOV from R9 rather than a memory load. Incoming args 7+ (BPF r11+16, r11+24, ...) map directly to [rbp + 16], [rbp + 24], ..., matching the x86-64 stack layout after CALL + PUSH RBP, so no offset adjustment is needed. tail_call_reachable is rejected by the verifier and priv_stack is disabled by the JIT when stack args exist, so R9 is always available. When BPF bytecode writes to the arg-6 stack slot (offset -8), the JIT emits a MOV into R9 instead of a memory store. Outgoing args 7+ are placed at [rsp] in a pre-allocated area below callee-saved registers, using: native_off = outgoing_arg_base - outgoing_rsp - bpf_off - 16 The native x86_64 stack layout with stack arguments: high address +-------------------------+ | incoming stack arg N | [rbp + 16 + (N-7)*8] (from caller) | ... | | incoming stack arg 7 | [rbp + 16] +-------------------------+ | return address | [rbp + 8] | saved rbp | [rbp] +-------------------------+ | BPF program stack | (round_up(stack_depth, 8) bytes) +-------------------------+ | callee-saved regs | (r12, rbx, r13, r14, r15 as needed) +-------------------------+ | outgoing arg M | [rsp + (M-7)*8] | ... | | outgoing arg 7 | [rsp] +-------------------------+ rsp low address Acked-by: Puranjay Mohan <puranjay@kernel.org> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20260513045122.2393118-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>