From: Puranjay Mohan Date: Thu, 28 May 2026 16:17:47 +0000 (-0700) Subject: bpf, arm64: Fix redundant MOV and clarify stack arg comments X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=12a585e607fa6e3fbe2c02158c7ad284cbf75792;p=thirdparty%2Flinux.git bpf, arm64: Fix redundant MOV and clarify stack arg comments emit_stack_arg_store_imm() materializes the immediate into tmp and then moves tmp to the target register (x5-x7). Emit the immediate directly into the target register to avoid the redundant MOV. While here, qualify the bare "FP" in the stack-layout ASCII art as "A64_FP" so it is not confused with BPF_FP, and note that incoming stack arguments sit above the FP/LR pair pushed by the callee prologue. Suggested-by: Will Deacon Signed-off-by: Puranjay Mohan Link: https://lore.kernel.org/r/20260528161750.1900674-2-puranjay@kernel.org Signed-off-by: Alexei Starovoitov --- diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index e3bbeaa94590..b4abc3138f37 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -546,7 +546,8 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) * low * * Stack args 6-8 are passed in x5-x7, args 9+ at [SP]. - * Incoming args 9+ are at [FP + 16], [FP + 24], ... + * Incoming args 9+ are at [A64_FP + 16], [A64_FP + 24], ... + * (above the saved FP/LR pair pushed in the callee prologue). */ emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx); @@ -1235,11 +1236,12 @@ static void emit_stack_arg_store_imm(s32 imm, s16 bpf_off, const u8 tmp, struct { int idx = -bpf_off / sizeof(u64) - 1; - emit_a64_mov_i(1, tmp, imm, ctx); - if (idx < NR_STACK_ARG_REGS) - emit(A64_MOV(1, stack_arg_reg[idx], tmp), ctx); - else + if (idx < NR_STACK_ARG_REGS) { + emit_a64_mov_i(1, stack_arg_reg[idx], imm, ctx); + } else { + emit_a64_mov_i(1, tmp, imm, ctx); emit(A64_STR64I(tmp, A64_SP, (idx - NR_STACK_ARG_REGS) * sizeof(u64)), ctx); + } } /* JITs an eBPF instruction.