From: George Guo When loading immediate values that fit within 12-bit signed range, the move_imm function incorrectly used zero extension instead of sign extension. The bug was exposed when scx_simple scheduler failed with -EINVAL in ops.init() after passing node = -1 to scx_bpf_create_dsq(). Due to incorrect sign extension, `node >= (int)nr_node_ids` evaluated to true instead of false, causing BPF program failure. Verified by testing with the scx_simple scheduler (located in tools/sched_ext/). After building with `make` and running ./tools/sched_ext/build/bin/scx_simple, the scheduler now initializes successfully with this fix. Fix this by using sign extension (sext) instead of zero extension for signed immediate values in move_imm. Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support") Reported-by: Bing Huang Signed-off-by: George Guo --- Signed-off-by: george --- arch/loongarch/net/bpf_jit.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/loongarch/net/bpf_jit.h b/arch/loongarch/net/bpf_jit.h index 5697158fd1645fdc3d83f598b00a9e20dfaa8f6d..f1398eb135b69ae61a27ed81f80b4bb0788cf0a0 100644 --- a/arch/loongarch/net/bpf_jit.h +++ b/arch/loongarch/net/bpf_jit.h @@ -122,7 +122,8 @@ static inline void move_imm(struct jit_ctx *ctx, enum loongarch_gpr rd, long imm /* addiw rd, $zero, imm_11_0 */ if (is_signed_imm12(imm)) { emit_insn(ctx, addiw, rd, LOONGARCH_GPR_ZERO, imm); - goto zext; + emit_sext_32(ctx, rd, is32); + return; } /* ori rd, $zero, imm_11_0 */ --- base-commit: 6146a0f1dfae5d37442a9ddcba012add260bceb0 change-id: 20251103-1-96faa240e8f4 Best regards, -- george