diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index 058ffbbaad85..a2a42c0a0f9d 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -9,7 +9,13 @@ #define LOONGARCH_MAX_REG_ARGS 8 +#define LOONGARCH_SAVE_RA_NINSNS 1 #define LOONGARCH_LONG_JUMP_NINSNS 5 +#define LOONGARCH_TCC_SLOT_NINSNS 1 + +#define LOONGARCH_PROLOGUE_SKIP_INSNS \ + (LOONGARCH_SAVE_RA_NINSNS + LOONGARCH_LONG_JUMP_NINSNS + LOONGARCH_TCC_SLOT_NINSNS) + #define LOONGARCH_LONG_JUMP_NBYTES (LOONGARCH_LONG_JUMP_NINSNS * 4) #define LOONGARCH_FENTRY_NINSNS 2 @@ -143,8 +149,13 @@ static void build_prologue(struct jit_ctx *ctx) stack_adjust = round_up(stack_adjust, 16); stack_adjust += bpf_stack_adjust; + /* + * Save the original return address to a temporary register to prevent + * it from being overwritten, then reserve space for the long jump and + * fentry trampoline slot for dynamically patching by ftrace at runtime. + * These instructions are bypassed during a tail call invocation. + */ move_reg(ctx, LOONGARCH_GPR_T0, LOONGARCH_GPR_RA); - /* Reserve space for the move_imm + jirl instruction */ for (i = 0; i < LOONGARCH_LONG_JUMP_NINSNS; i++) emit_insn(ctx, nop); @@ -253,10 +264,11 @@ static void __build_epilogue(struct jit_ctx *ctx, bool is_tail_call) emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_RA, 0); } else { /* - * Call the next bpf prog and skip the first instruction - * of TCC initialization. + * Tail call to the next BPF program, passing offset in number + * of instructions to jirl to bypass the initial setup slots. */ - emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_T3, 7); + emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, + LOONGARCH_GPR_T3, LOONGARCH_PROLOGUE_SKIP_INSNS); } }