The arm64 JIT supports BPF_ST with BPF_PROBE_MEM32 (arena) by using the tmp2 register to hold the dst + arena_vm_base value and using tmp2 as the new dst register. But this is broken because in case is_lsi_offset() returns false the tmp2 will be clobbered by emit_a64_mov_i(1, tmp2, off, ctx); and hence the emitted store instruction will be of the form: strb w10, [x11, x11] Fix this by using the third temporary register to hold the dst + arena_vm_base. Fixes: 339af577ec05 ("bpf: Add arm64 JIT support for PROBE_MEM32 pseudo instructions.") Signed-off-by: Puranjay Mohan --- Changes in v1->v2: v1: https://lore.kernel.org/bpf/20251030120146.50417-1-puranjay@kernel.org/ - Fix the build issue by declaring tmp3 in the right function. --- arch/arm64/net/bpf_jit_comp.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index ab83089c3d8f..0c9a50a1e73e 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1213,6 +1213,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, u8 src = bpf2a64[insn->src_reg]; const u8 tmp = bpf2a64[TMP_REG_1]; const u8 tmp2 = bpf2a64[TMP_REG_2]; + const u8 tmp3 = bpf2a64[TMP_REG_3]; const u8 fp = bpf2a64[BPF_REG_FP]; const u8 arena_vm_base = bpf2a64[ARENA_VM_START]; const u8 priv_sp = bpf2a64[PRIVATE_SP]; @@ -1757,8 +1758,8 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, case BPF_ST | BPF_PROBE_MEM32 | BPF_W: case BPF_ST | BPF_PROBE_MEM32 | BPF_DW: if (BPF_MODE(insn->code) == BPF_PROBE_MEM32) { - emit(A64_ADD(1, tmp2, dst, arena_vm_base), ctx); - dst = tmp2; + emit(A64_ADD(1, tmp3, dst, arena_vm_base), ctx); + dst = tmp3; } if (dst == fp) { dst_adj = ctx->priv_sp_used ? priv_sp : A64_SP; -- 2.47.3