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bpf, riscv: Add BPF stack arguments support for RV64 JIT #13292

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676e8b9
bpf, riscv: Add BPF stack arguments support for RV64 JIT
flynnjiang Aug 14, 2026
a56754c
selftests/bpf: Enable stack argument tests for RV64
flynnjiang Aug 14, 2026
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1 change: 1 addition & 0 deletions arch/riscv/net/bpf_jit.h
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,7 @@ struct rv_jit_context {
unsigned long flags;
int stack_size;
int tcc_offset;
u16 stack_arg_size;
u64 arena_vm_start;
u64 user_vm_start;
};
Expand Down
79 changes: 76 additions & 3 deletions arch/riscv/net/bpf_jit_comp64.c
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Expand Up @@ -1815,19 +1815,44 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,

if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
const struct btf_func_model *fm;
int idx;
int idx, nargs;

fm = bpf_jit_find_kfunc_model(ctx->prog, insn);
if (!fm)
return -EINVAL;

for (idx = 0; idx < fm->nr_args; idx++) {
nargs = min_t(int, fm->nr_args, MAX_BPF_FUNC_REG_ARGS);
for (idx = 0; idx < nargs; idx++) {
u8 reg = bpf_to_rv_reg(BPF_REG_1 + idx, ctx);
bool sign = fm->arg_flags[idx] & BTF_FMODEL_SIGNED_ARG;

if (sign_extend(reg, reg, fm->arg_size[idx], sign, ctx))
return -EINVAL;
}

/* BPF stack args -> RISC-V ABI: args 6-8 in A5-A7, 9+ at SP+0 */
if (fm->nr_args > MAX_BPF_FUNC_REG_ARGS) {
int n_stack = fm->nr_args - MAX_BPF_FUNC_REG_ARGS;
int n_reg = min_t(int, n_stack,
RV_MAX_REG_ARGS - MAX_BPF_FUNC_REG_ARGS);

for (idx = 0; idx < n_reg; idx++) {
int sz = fm->arg_size[MAX_BPF_FUNC_REG_ARGS + idx];

emit_ld(RV_REG_A5 + idx, idx * 8, RV_REG_SP, ctx);
if (sz == sizeof(int))
emit_sextw(RV_REG_A5 + idx, RV_REG_A5 + idx, ctx);
}

for (idx = n_reg; idx < n_stack; idx++) {
int sz = fm->arg_size[MAX_BPF_FUNC_REG_ARGS + idx];

emit_ld(RV_REG_T1, idx * 8, RV_REG_SP, ctx);
if (sz == sizeof(int))
emit_sextw(RV_REG_T1, RV_REG_T1, ctx);
emit_sd(RV_REG_SP, (idx - n_reg) * 8, RV_REG_T1, ctx);
}
}
}

/* restore TCC to RV_REG_TCC before bpf2bpf call */
Expand Down Expand Up @@ -1892,6 +1917,21 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_LDX | BPF_MEM | BPF_H:
case BPF_LDX | BPF_MEM | BPF_W:
case BPF_LDX | BPF_MEM | BPF_DW:
if (insn->src_reg == BPF_REG_PARAMS) {
int idx = off / 8 - 1;

if (is_12b_int(idx * 8)) {
emit_ldx_insn(rd, idx * 8, RV_REG_FP, BPF_SIZE(code), false, ctx);
} else {
emit_imm(RV_REG_T1, idx * 8, ctx);
emit_add(RV_REG_T1, RV_REG_T1, RV_REG_FP, ctx);
emit_ldx_insn(rd, 0, RV_REG_T1, BPF_SIZE(code), false, ctx);
}
if (BPF_SIZE(code) != BPF_DW && insn_is_zext(&insn[1]))
return 1;
break;
}
fallthrough;
case BPF_LDX | BPF_PROBE_MEM | BPF_B:
case BPF_LDX | BPF_PROBE_MEM | BPF_H:
case BPF_LDX | BPF_PROBE_MEM | BPF_W:
Expand Down Expand Up @@ -1939,6 +1979,20 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_ST | BPF_MEM | BPF_H:
case BPF_ST | BPF_MEM | BPF_W:
case BPF_ST | BPF_MEM | BPF_DW:
if (insn->dst_reg == BPF_REG_PARAMS) {
int idx = -off / 8 - 1;

emit_imm(RV_REG_T1, imm, ctx);
if (is_12b_int(idx * 8)) {
emit_stx_insn(RV_REG_SP, idx * 8, RV_REG_T1, BPF_SIZE(code), ctx);
} else {
emit_imm(RV_REG_T2, idx * 8, ctx);
emit_add(RV_REG_T2, RV_REG_SP, RV_REG_T2, ctx);
emit_stx_insn(RV_REG_T2, 0, RV_REG_T1, BPF_SIZE(code), ctx);
}
break;
}
fallthrough;
/* ST | PROBE_MEM32: *(size *)(dst + RV_REG_ARENA + off) = imm */
case BPF_ST | BPF_PROBE_MEM32 | BPF_B:
case BPF_ST | BPF_PROBE_MEM32 | BPF_H:
Expand All @@ -1961,6 +2015,19 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
case BPF_STX | BPF_MEM | BPF_H:
case BPF_STX | BPF_MEM | BPF_W:
case BPF_STX | BPF_MEM | BPF_DW:
if (insn->dst_reg == BPF_REG_PARAMS) {
int idx = -off / 8 - 1;

if (is_12b_int(idx * 8)) {
emit_stx_insn(RV_REG_SP, idx * 8, rs, BPF_SIZE(code), ctx);
} else {
emit_imm(RV_REG_T1, idx * 8, ctx);
emit_add(RV_REG_T1, RV_REG_SP, RV_REG_T1, ctx);
emit_stx_insn(RV_REG_T1, 0, rs, BPF_SIZE(code), ctx);
}
break;
}
fallthrough;
/* STX | PROBE_MEM32: *(size *)(dst + RV_REG_ARENA + off) = src */
case BPF_STX | BPF_PROBE_MEM32 | BPF_B:
case BPF_STX | BPF_PROBE_MEM32 | BPF_H:
Expand Down Expand Up @@ -2046,6 +2113,7 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog)

stack_adjust = round_up(stack_adjust, STACK_ALIGN);
stack_adjust += bpf_stack_adjust;
stack_adjust += ctx->stack_arg_size;

store_offset = stack_adjust - 8;

Expand Down Expand Up @@ -2103,7 +2171,7 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog)
emit_addi(RV_REG_FP, RV_REG_SP, stack_adjust, ctx);

if (bpf_stack_adjust)
emit_addi(RV_REG_S5, RV_REG_SP, bpf_stack_adjust, ctx);
emit_addi(RV_REG_S5, RV_REG_SP, ctx->stack_arg_size + bpf_stack_adjust, ctx);

ctx->stack_size = stack_adjust;

Expand Down Expand Up @@ -2181,3 +2249,8 @@ bool bpf_jit_supports_timed_may_goto(void)
{
return true;
}

bool bpf_jit_supports_stack_args(void)
{
return true;
}
4 changes: 4 additions & 0 deletions arch/riscv/net/bpf_jit_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,10 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr
ctx->arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena);
ctx->user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena);
ctx->prog = prog;

ctx->stack_arg_size = round_up(bpf_out_stack_arg_cnt(env, prog) *
sizeof(u64), STACK_ALIGN);

ctx->offset = kvzalloc_objs(int, prog->len);
if (!ctx->offset)
goto out_offset;
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c
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Expand Up @@ -4,7 +4,8 @@
#include <bpf/bpf_helpers.h>
#include "../test_kmods/bpf_testmod_kfunc.h"

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

long subprog_call_mem_kfunc(long a, long b, long c, long d, long e, long size)
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/btf__verifier_stack_arg_order.c
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Expand Up @@ -3,7 +3,8 @@
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

int subprog_bad_order_6args(int a, int b, int c, int d, int e, int f)
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/stack_arg.c
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Expand Up @@ -21,7 +21,8 @@ struct {

int timer_result;

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

const volatile bool has_stack_arg = true;
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/stack_arg_kfunc.c
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Expand Up @@ -6,7 +6,8 @@
#include "bpf_kfuncs.h"
#include "../test_kmods/bpf_testmod_kfunc.h"

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

const volatile bool has_stack_arg = true;
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/stack_arg_precision.c
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Expand Up @@ -6,7 +6,8 @@
#include "../test_kmods/bpf_testmod_kfunc.h"
#include "bpf_misc.h"

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

/* Force kfunc extern BTF generation for inline asm call below.
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/verifier_stack_arg.c
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Expand Up @@ -12,7 +12,8 @@ struct {
__type(value, long long);
} map_hash_8b SEC(".maps");

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

__noinline __used
Expand Down
3 changes: 2 additions & 1 deletion tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c
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Expand Up @@ -5,7 +5,8 @@
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"

#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \
#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)) && \
defined(__BPF_FEATURE_STACK_ARGUMENT)

__noinline __used __naked
Expand Down
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