Merge branch 'bpf-riscv-add-support-for-indirect-jumps'

Chen Pei says:

====================
bpf, riscv: Add support for indirect jumps

The indirect jump instruction (BPF_JMP | BPF_JA | BPF_X, "gotox") and the
BPF_MAP_TYPE_INSN_ARRAY jump tables it consumes are core features: the
verifier accepts them on every architecture, and the x86-64, arm64 and
powerpc JITs implement them. On riscv64 a program using gotox passes
verification and then fails to load, because the JIT does not know the
opcode and CONFIG_BPF_JIT_ALWAYS_ON leaves no interpreter to fall back
onto.

This series adds the riscv64 support and turns the existing selftests on
for that architecture.

Patch 1 emits "jalr zero, rd, 0" for gotox and publishes the xlated to
jitted offsets through bpf_prog_update_insn_ptrs(), which is what fills
in the jump table addresses. Patches 2 to 4 widen the arch guards in
verifier_gotox.c, compute_live_registers.c and bpf_insn_array.c to
riscv64, the same way the other architectures were enabled.

Changes since v2:
- Pick up Pu Lehui's Reviewed-by on patch 1.
- Enable two more gotox test files for riscv64: compute_live_registers.c
  and bpf_insn_array.c.

Changes since v1:
- Rebased onto bpf-next.
- Patch 1: reword the code comment to say "shift ctx->offset[] by one".
- Patch 2: collapse the multi-line #endif marker to a single line.
- Added Reviewed-by/Acked-by from Björn Töpel.

Testing
=======

Environment: QEMU virt rv64, with CONFIG_BPF_JIT=y,
CONFIG_BPF_JIT_ALWAYS_ON=y, CONFIG_DEBUG_INFO_BTF=y; selftests
cross-built with clang 23.

- test_progs -t verifier_gotox: 33/33 subtests pass.
- test_progs -t bpf_insn_array: 20/20 subtests pass.
- test_progs -t compute_live_registers: 20/20 subtests pass, including
  the gotox liveness subtest.
- test_progs-cpuv4 -t bpf_gotox: 14/14 subtests pass.
====================

Link: https://patch.msgid.link/20260928071845.2432-1-cp0613@linux.alibaba.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/riscv/net/bpf_jit_comp64.c

@@ -1719,6 +1719,11 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 			emit_zextw(rd, rd, ctx);
 		break;
 
+	/* JUMP reg */
+	case BPF_JMP | BPF_JA | BPF_X:
+		emit_jalr(RV_REG_ZERO, rd, 0, ctx);
+		break;
+
 	/* JUMP off */
 	case BPF_JMP | BPF_JA:
 	case BPF_JMP32 | BPF_JA:

arch/riscv/net/bpf_jit_core.c

@@ -26,10 +26,13 @@ static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
 		int ret;
 
 		ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
-		if (ret > 0)
-			i++; /* skip the next instruction */
 		if (offset)
 			offset[i] = ctx->ninsns;
+		if (ret > 0) {
+			i++; /* skip the next instruction */
+			if (offset)
+				offset[i] = ctx->ninsns;
+		}
 		if (ret < 0)
 			return ret;
 	}
@@ -176,6 +179,15 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr
 		for (i = 0; i < prog->len; i++)
 			ctx->offset[i] = ninsns_rvoff(ctx->offset[i]);
 		bpf_prog_fill_jited_linfo(prog, ctx->offset);
+
+		/*
+		 * bpf_prog_update_insn_ptrs() wants the start of each insn, so
+		 * shift ctx->offset[] by one and get insn 0 from the prologue.
+		 */
+		for (i = prog->len - 1; i > 0; i--)
+			ctx->offset[i] = ctx->offset[i - 1];
+		ctx->offset[0] = ninsns_rvoff(ctx->prologue_len);
+		bpf_prog_update_insn_ptrs(prog, ctx->offset, jit_data->ro_image);
 out_offset:
 		kvfree(ctx->offset);
 		kfree(jit_data);

tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c

@@ -4,7 +4,8 @@
 #include <bpf/btf.h>
 #include <test_progs.h>
 
-#if defined(__x86_64__) || defined(__powerpc__) || defined(__aarch64__)
+#if defined(__x86_64__) || defined(__powerpc__) || defined(__aarch64__) || \
+	(defined(__riscv) && __riscv_xlen == 64)
 static int map_create(__u32 map_type, __u32 max_entries)
 {
 	const char *map_name = "insn_array";

tools/testing/selftests/bpf/progs/compute_live_registers.c

@@ -496,7 +496,8 @@ __naked void subprog_ret_reg_pair(void)
 		::: __clobber_all);
 }
 
-#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)
 
 SEC("socket")
 __log_level(2)
@@ -535,7 +536,7 @@ void gotox(void)
 	: __clobber_all);
 }
 
-#endif /* __TARGET_ARCH_x86 || __TARGET_ARCH_arm64 */
+#endif /* gotox: x86, arm64, riscv64 */
 
 /* to retain debug info for BTF generation */
 void kfunc_root(void)

tools/testing/selftests/bpf/progs/verifier_gotox.c

@@ -6,7 +6,9 @@
 #include "bpf_misc.h"
 #include "../../../include/linux/filter.h"
 
-#if defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_powerpc)
+#if defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64) || \
+	defined(__TARGET_ARCH_powerpc) || \
+	(defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64)
 
 #define DEFINE_SIMPLE_JUMP_TABLE_PROG(NAME, SRC_REG, OFF, IMM, OUTCOME)	\
 									\
@@ -586,6 +588,6 @@ nop_%=:								\
 	: __clobber_all);
 }
 
-#endif /* __TARGET_ARCH_x86 || __TARGET_ARCH_arm64 || __TARGET_ARCH_powerpc*/
+#endif /* gotox: x86, arm64, powerpc, riscv64 */
 
 char _license[] SEC("license") = "GPL";