#define SEEN_NVREG_FULL_MASK 0x0003ffff /* Non volatile registers r14-r31 */
#define SEEN_NVREG_TEMP_MASK 0x00001e01 /* BPF_REG_5, BPF_REG_AX, TMP_REG */
+static inline bool bpf_has_stack_frame(struct codegen_context *ctx)
+{
+ /*
+ * We only need a stack frame if:
+ * - we call other functions (kernel helpers), or
+ * - we use non volatile registers, or
+ * - we use tail call counter
+ * - the bpf program uses its stack area
+ * The latter condition is deduced from the usage of BPF_REG_FP
+ */
+ return ctx->seen & (SEEN_FUNC | SEEN_TAILCALL | SEEN_NVREG_FULL_MASK) ||
+ bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP));
+}
+
void bpf_jit_realloc_regs(struct codegen_context *ctx)
{
unsigned int nvreg_mask;
#define BPF_TAILCALL_PROLOGUE_SIZE 4
- EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
+ if (bpf_has_stack_frame(ctx))
+ EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
if (ctx->seen & SEEN_TAILCALL)
EMIT(PPC_RAW_STW(_R4, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC)));
EMIT(PPC_RAW_LWZ(_R0, _R1, BPF_PPC_STACKFRAME(ctx) + PPC_LR_STKOFF));
/* Tear down our stack frame */
- EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx)));
+ if (bpf_has_stack_frame(ctx))
+ EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx)));
if (ctx->seen & SEEN_FUNC)
EMIT(PPC_RAW_MTLR(_R0));