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riscv, bpf: Optimize calls
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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 <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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@bjoto @borkmann
bjoto authored and borkmann committed Dec 19, 2019
1 parent 7f3631e commit e368b64
Showing 1 changed file with 64 additions and 37 deletions.
101 changes: 64 additions & 37 deletions arch/riscv/net/bpf_jit_comp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
Expand All @@ -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)
{
Expand Down Expand Up @@ -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 */
Expand Down Expand Up @@ -1209,28 +1232,17 @@ 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);
ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass, &addr,
&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 */
Expand All @@ -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 */
Expand Down Expand Up @@ -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;
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down

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