Commit bafb5898 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/bpf: Emit a single branch instruction for known short branch ranges 



PPC_BCC() emits two instructions to accommodate scenarios where we need
to branch outside the range of a conditional branch. PPC_BCC_SHORT()
emits a single branch instruction and can be used when the branch is
known to be within a conditional branch range.

Convert some of the uses of PPC_BCC() in the powerpc BPF JIT over to
PPC_BCC_SHORT() where we know the branch range.

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/edbca01377d1d5f472868bf6d8962b0a0d85b96f.1644834730.git.naveen.n.rao@linux.vnet.ibm.com
parent acd7408d

arch/powerpc/net/bpf_jit_comp32.c

+4 −4
Original line number Diff line number Diff line
@@ -229,7 +229,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	EMIT(PPC_RAW_LWZ(_R0, b2p_bpf_array, offsetof(struct bpf_array, map.max_entries)));

	EMIT(PPC_RAW_CMPLW(b2p_index, _R0));

	EMIT(PPC_RAW_LWZ(_R0, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC)));

	PPC_BCC(COND_GE, out);

	PPC_BCC_SHORT(COND_GE, out);



	/*

	 * if (tail_call_cnt >= MAX_TAIL_CALL_CNT)
@@ -238,7 +238,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	EMIT(PPC_RAW_CMPLWI(_R0, MAX_TAIL_CALL_CNT));

	/* tail_call_cnt++; */

	EMIT(PPC_RAW_ADDIC(_R0, _R0, 1));

	PPC_BCC(COND_GE, out);

	PPC_BCC_SHORT(COND_GE, out);



	/* prog = array->ptrs[index]; */

	EMIT(PPC_RAW_RLWINM(_R3, b2p_index, 2, 0, 29));
@@ -251,7 +251,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	 *   goto out;

	 */

	EMIT(PPC_RAW_CMPLWI(_R3, 0));

	PPC_BCC(COND_EQ, out);

	PPC_BCC_SHORT(COND_EQ, out);



	/* goto *(prog->bpf_func + prologue_size); */

	EMIT(PPC_RAW_LWZ(_R3, _R3, offsetof(struct bpf_prog, bpf_func)));
@@ -842,7 +842,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * 
			if (BPF_MODE(code) == BPF_PROBE_MEM) {

				PPC_LI32(_R0, TASK_SIZE - off);

				EMIT(PPC_RAW_CMPLW(src_reg, _R0));

				PPC_BCC(COND_GT, (ctx->idx + 5) * 4);

				PPC_BCC_SHORT(COND_GT, (ctx->idx + 4) * 4);

				EMIT(PPC_RAW_LI(dst_reg, 0));

				/*

				 * For BPF_DW case, "li reg_h,0" would be needed when

arch/powerpc/net/bpf_jit_comp64.c

+4 −4
Original line number Diff line number Diff line
@@ -225,7 +225,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	EMIT(PPC_RAW_LWZ(b2p[TMP_REG_1], b2p_bpf_array, offsetof(struct bpf_array, map.max_entries)));

	EMIT(PPC_RAW_RLWINM(b2p_index, b2p_index, 0, 0, 31));

	EMIT(PPC_RAW_CMPLW(b2p_index, b2p[TMP_REG_1]));

	PPC_BCC(COND_GE, out);

	PPC_BCC_SHORT(COND_GE, out);



	/*

	 * if (tail_call_cnt >= MAX_TAIL_CALL_CNT)
@@ -233,7 +233,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	 */

	PPC_BPF_LL(b2p[TMP_REG_1], 1, bpf_jit_stack_tailcallcnt(ctx));

	EMIT(PPC_RAW_CMPLWI(b2p[TMP_REG_1], MAX_TAIL_CALL_CNT));

	PPC_BCC(COND_GE, out);

	PPC_BCC_SHORT(COND_GE, out);



	/*

	 * tail_call_cnt++;
@@ -251,7 +251,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o 
	 *   goto out;

	 */

	EMIT(PPC_RAW_CMPLDI(b2p[TMP_REG_1], 0));

	PPC_BCC(COND_EQ, out);

	PPC_BCC_SHORT(COND_EQ, out);



	/* goto *(prog->bpf_func + prologue_size); */

	PPC_BPF_LL(b2p[TMP_REG_1], b2p[TMP_REG_1], offsetof(struct bpf_prog, bpf_func));
@@ -807,7 +807,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * 
				else /* BOOK3S_64 */

					PPC_LI64(b2p[TMP_REG_2], PAGE_OFFSET);

				EMIT(PPC_RAW_CMPLD(b2p[TMP_REG_1], b2p[TMP_REG_2]));

				PPC_BCC(COND_GT, (ctx->idx + 4) * 4);

				PPC_BCC_SHORT(COND_GT, (ctx->idx + 3) * 4);

				EMIT(PPC_RAW_LI(dst_reg, 0));

				/*

				 * Check if 'off' is word aligned because PPC_BPF_LL()