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Date: Mon, 16 Dec 2019 10:13:41 +0100
From: Björn Töpel <bjorn.topel@...il.com>
To: daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org
Cc: Björn Töpel <bjorn.topel@...il.com>,
linux-riscv@...ts.infradead.org, bpf@...r.kernel.org
Subject: [PATCH bpf-next v2 7/9] riscv, bpf: optimize calls
Instead of using emit_imm() and emit_jalr() which can expand to six
instructions, start using jal or auipc+jalr.
Signed-off-by: Björn Töpel <bjorn.topel@...il.com>
---
arch/riscv/net/bpf_jit_comp.c | 101 +++++++++++++++++++++-------------
1 file changed, 64 insertions(+), 37 deletions(-)
diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c
index 46cff093f526..8d7e3343a08c 100644
--- a/arch/riscv/net/bpf_jit_comp.c
+++ b/arch/riscv/net/bpf_jit_comp.c
@@ -811,11 +811,12 @@ static void emit_sext_32_rd(u8 *rd, struct rv_jit_context *ctx)
*rd = RV_REG_T2;
}
-static void emit_jump_and_link(u8 rd, int rvoff, struct rv_jit_context *ctx)
+static void emit_jump_and_link(u8 rd, s64 rvoff, bool force_jalr,
+ struct rv_jit_context *ctx)
{
s64 upper, lower;
- if (is_21b_int(rvoff)) {
+ if (rvoff && is_21b_int(rvoff) && !force_jalr) {
emit(rv_jal(rd, rvoff >> 1), ctx);
return;
}
@@ -832,6 +833,28 @@ static bool is_signed_bpf_cond(u8 cond)
cond == BPF_JSGE || cond == BPF_JSLE;
}
+static int emit_call(bool fixed, u64 addr, struct rv_jit_context *ctx)
+{
+ s64 off = 0;
+ u64 ip;
+ u8 rd;
+
+ if (addr && ctx->insns) {
+ ip = (u64)(long)(ctx->insns + ctx->ninsns);
+ off = addr - ip;
+ if (!is_32b_int(off)) {
+ pr_err("bpf-jit: target call addr %pK is out of range\n",
+ (void *)addr);
+ return -ERANGE;
+ }
+ }
+
+ emit_jump_and_link(RV_REG_RA, off, !fixed, ctx);
+ rd = bpf_to_rv_reg(BPF_REG_0, ctx);
+ emit(rv_addi(rd, RV_REG_A0, 0), ctx);
+ return 0;
+}
+
static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
bool extra_pass)
{
@@ -1107,7 +1130,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
/* JUMP off */
case BPF_JMP | BPF_JA:
rvoff = rv_offset(i, off, ctx);
- emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
+ emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx);
break;
/* IF (dst COND src) JUMP off */
@@ -1209,7 +1232,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_JMP | BPF_CALL:
{
bool fixed;
- int i, ret;
+ int ret;
u64 addr;
mark_call(ctx);
@@ -1217,20 +1240,9 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
&fixed);
if (ret < 0)
return ret;
- if (fixed) {
- emit_imm(RV_REG_T1, addr, ctx);
- } else {
- i = ctx->ninsns;
- emit_imm(RV_REG_T1, addr, ctx);
- for (i = ctx->ninsns - i; i < 8; i++) {
- /* nop */
- emit(rv_addi(RV_REG_ZERO, RV_REG_ZERO, 0),
- ctx);
- }
- }
- emit(rv_jalr(RV_REG_RA, RV_REG_T1, 0), ctx);
- rd = bpf_to_rv_reg(BPF_REG_0, ctx);
- emit(rv_addi(rd, RV_REG_A0, 0), ctx);
+ ret = emit_call(fixed, addr, ctx);
+ if (ret)
+ return ret;
break;
}
/* tail call */
@@ -1245,7 +1257,7 @@ static int emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
break;
rvoff = epilogue_offset(ctx);
- emit_jump_and_link(RV_REG_ZERO, rvoff, ctx);
+ emit_jump_and_link(RV_REG_ZERO, rvoff, false, ctx);
break;
/* dst = imm64 */
@@ -1508,7 +1520,7 @@ static void build_epilogue(struct rv_jit_context *ctx)
__build_epilogue(false, ctx);
}
-static int build_body(struct rv_jit_context *ctx, bool extra_pass)
+static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
{
const struct bpf_prog *prog = ctx->prog;
int i;
@@ -1520,12 +1532,12 @@ static int build_body(struct rv_jit_context *ctx, bool extra_pass)
ret = emit_insn(insn, ctx, extra_pass);
if (ret > 0) {
i++;
- if (ctx->insns == NULL)
- ctx->offset[i] = ctx->ninsns;
+ if (offset)
+ offset[i] = ctx->ninsns;
continue;
}
- if (ctx->insns == NULL)
- ctx->offset[i] = ctx->ninsns;
+ if (offset)
+ offset[i] = ctx->ninsns;
if (ret)
return ret;
}
@@ -1553,8 +1565,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
struct bpf_prog *tmp, *orig_prog = prog;
int pass = 0, prev_ninsns = 0, i;
struct rv_jit_data *jit_data;
+ unsigned int image_size = 0;
struct rv_jit_context *ctx;
- unsigned int image_size;
if (!prog->jit_requested)
return orig_prog;
@@ -1599,36 +1611,51 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
for (i = 0; i < 16; i++) {
pass++;
ctx->ninsns = 0;
- if (build_body(ctx, extra_pass)) {
+ if (build_body(ctx, extra_pass, ctx->offset)) {
prog = orig_prog;
goto out_offset;
}
build_prologue(ctx);
ctx->epilogue_offset = ctx->ninsns;
build_epilogue(ctx);
- if (ctx->ninsns == prev_ninsns)
- break;
+
+ if (ctx->ninsns == prev_ninsns) {
+ if (jit_data->header)
+ break;
+
+ image_size = sizeof(u32) * ctx->ninsns;
+ jit_data->header =
+ bpf_jit_binary_alloc(image_size,
+ &jit_data->image,
+ sizeof(u32),
+ bpf_fill_ill_insns);
+ if (!jit_data->header) {
+ prog = orig_prog;
+ goto out_offset;
+ }
+
+ ctx->insns = (u32 *)jit_data->image;
+ /* Now, when the image is allocated, the image
+ * can potentially shrink more (auipc/jalr ->
+ * jal).
+ */
+ }
prev_ninsns = ctx->ninsns;
}
- /* Allocate image, now that we know the size. */
- image_size = sizeof(u32) * ctx->ninsns;
- jit_data->header = bpf_jit_binary_alloc(image_size, &jit_data->image,
- sizeof(u32),
- bpf_fill_ill_insns);
- if (!jit_data->header) {
+ if (i == 16) {
+ pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
+ bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
}
- /* Second, real pass, that acutally emits the image. */
- ctx->insns = (u32 *)jit_data->image;
skip_init_ctx:
pass++;
ctx->ninsns = 0;
build_prologue(ctx);
- if (build_body(ctx, extra_pass)) {
+ if (build_body(ctx, extra_pass, NULL)) {
bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
--
2.20.1
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