From 536b523b407397c8d3967c020ce7aad70a0ea030 Mon Sep 17 00:00:00 2001 From: Chen Pei Date: Wed, 2 Sep 2026 14:14:51 +0800 Subject: [PATCH] bpf, riscv: Make arena support depend on ZACAS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The arena range tree allocates its nodes with kmalloc_nolock() since commit f8c67d8550ee ("bpf: Use kmalloc_nolock() in range tree"). kmalloc_nolock() requires slab caches with cmpxchg128 support (__CMPXCHG_DOUBLE); on riscv cmpxchg128 is provided by the ZACAS extension. On systems without ZACAS every arena map creation fails with a misleading -ENOMEM. Report the missing support instead: make bpf_jit_supports_arena() return system_has_cmpxchg128() where it is defined, so arena map creation fails with -EOPNOTSUPP on systems without ZACAS. The macro is only defined when both CONFIG_RISCV_ISA_ZACAS and CONFIG_TOOLCHAIN_HAS_ZACAS are enabled, so guard it with #ifdef the same way mm/slab.h consumes it, and reject arena otherwise. This matches how arena BPF_CMPXCHG instructions are already gated on ZACAS in bpf_jit_supports_insn(). Fixes: f8c67d8550ee ("bpf: Use kmalloc_nolock() in range tree") Signed-off-by: Chen Pei Acked-by: Pu Lehui Acked-by: Björn Töpel Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20260902061451.1416-1-cp0613@linux.alibaba.com Signed-off-by: Kumar Kartikeya Dwivedi --- arch/riscv/net/bpf_jit_comp64.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 74efe4b138d2..151031e97a24 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -2128,7 +2128,15 @@ bool bpf_jit_supports_ptr_xchg(void) bool bpf_jit_supports_arena(void) { - return true; + /* + * The arena range tree uses kmalloc_nolock(), which needs + * cmpxchg128, provided by ZACAS on riscv. + */ +#ifdef system_has_cmpxchg128 + return system_has_cmpxchg128(); +#else + return false; +#endif } bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)