[PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support · Björn Töpel <hidden> · 2019-12-16
[PATCH bpf-next v2 1/9] riscv, bpf: fix broken BPF tail calls · Björn Töpel <hidden> · 2019-12-16
[PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 3/9] riscv, bpf: add support for far branching when emitting tail call · Palmer Dabbelt <hidden> · 2019-12-23
[PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching · Palmer Dabbelt <hidden> · 2019-12-23
Re: [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching · Björn Töpel <hidden> · 2020-01-07
Re: [PATCH bpf-next v2 2/9] riscv, bpf: add support for far branching · Palmer Dabbelt <hidden> · 2020-01-23
[PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 4/9] riscv, bpf: add support for far jumps and exits · Palmer Dabbelt <hidden> · 2019-12-23
[PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls · Palmer Dabbelt <hidden> · 2019-12-23
[PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Daniel Borkmann <daniel@iogearbox.net> · 2019-12-16
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Björn Töpel <hidden> · 2019-12-18
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Paul Walmsley <hidden> · 2020-01-04
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Björn Töpel <hidden> · 2020-01-07
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Paul Walmsley <hidden> · 2020-01-07
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Palmer Dabbelt <hidden> · 2019-12-23
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Alex Ghiti <alex@ghiti.fr> · 2020-02-02
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Björn Töpel <hidden> · 2020-02-03
Re: [PATCH bpf-next v2 6/9] riscv, bpf: provide RISC-V specific JIT image alloc/free · Alex Ghiti <alex@ghiti.fr> · 2020-02-03
[PATCH bpf-next v2 7/9] riscv, bpf: optimize calls · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls · Palmer Dabbelt <hidden> · 2019-12-23
Re: [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls · Björn Töpel <hidden> · 2020-01-07
Re: [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls · Palmer Dabbelt <hidden> · 2020-01-28
Re: [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls · Björn Töpel <hidden> · 2020-02-03
[PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 8/9] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs · Palmer Dabbelt <hidden> · 2019-12-23
[PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs · Björn Töpel <hidden> · 2019-12-16
Re: [PATCH bpf-next v2 9/9] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs · Palmer Dabbelt <hidden> · 2019-12-23
Re: [PATCH bpf-next v2 0/9] riscv: BPF JIT fix, optimizations and far jumps support · Daniel Borkmann <daniel@iogearbox.net> · 2019-12-19

STALE2365d LANDED

Revisions (2)

2019-12-09 v1 [diff vs current]
2019-12-16 v2 current

[PATCH bpf-next v2 5/9] riscv, bpf: optimize BPF tail calls

From: Björn Töpel <hidden>
Date: 2019-12-16 09:14:10
Also in: bpf, linux-riscv
Subsystem: bpf jit for risc-v (32-bit), bpf jit for risc-v (64-bit), bpf [general] (safe dynamic programs and tools), risc-v architecture, the rest · Maintainers: Luke Nelson, Xi Wang, Björn Töpel, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Paul Walmsley, Palmer Dabbelt, Albert Ou, Linus Torvalds

Remove one addi, and instead use the offset part of jalr.

Signed-off-by: Björn Töpel <redacted>
---
 arch/riscv/net/bpf_jit_comp.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
index 2fc0f24ad30f..8aa19c846881 100644
--- a/arch/riscv/net/bpf_jit_comp.c
+++ b/arch/riscv/net/bpf_jit_comp.c

@@ -552,7 +552,7 @@ static int epilogue_offset(struct rv_jit_context *ctx)
 	return (to - from) << 2;
 }
 
-static void __build_epilogue(u8 reg, struct rv_jit_context *ctx)
+static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx)
 {
 	int stack_adjust = ctx->stack_size, store_offset = stack_adjust - 8;

@@ -589,9 +589,11 @@ static void __build_epilogue(u8 reg, struct rv_jit_context *ctx)
 
 	emit(rv_addi(RV_REG_SP, RV_REG_SP, stack_adjust), ctx);
 	/* Set return value. */
-	if (reg == RV_REG_RA)
+	if (!is_tail_call)
 		emit(rv_addi(RV_REG_A0, RV_REG_A5, 0), ctx);
-	emit(rv_jalr(RV_REG_ZERO, reg, 0), ctx);
+	emit(rv_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA,
+		     is_tail_call ? 4 : 0), /* skip TCC init */
+	     ctx);
 }
 
 /* return -1 or inverted cond */

@@ -751,9 +753,8 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx)
 	if (is_12b_check(off, insn))
 		return -1;
 	emit(rv_ld(RV_REG_T3, off, RV_REG_T2), ctx);
-	emit(rv_addi(RV_REG_T3, RV_REG_T3, 4), ctx);
 	emit(rv_addi(RV_REG_TCC, RV_REG_T1, 0), ctx);
-	__build_epilogue(RV_REG_T3, ctx);
+	__build_epilogue(true, ctx);
 	return 0;
 }

@@ -1504,7 +1505,7 @@ static void build_prologue(struct rv_jit_context *ctx)
 
 static void build_epilogue(struct rv_jit_context *ctx)
 {
-	__build_epilogue(RV_REG_RA, ctx);
+	__build_epilogue(false, ctx);
 }
 
 static int build_body(struct rv_jit_context *ctx, bool extra_pass)

-- 
2.20.1