[PATCH bpf-next] bpf: handle CONFIG_SMP=n configuration in x86 BPF JIT

[PATCH bpf-next] bpf: handle CONFIG_SMP=n configuration in x86 BPF JIT

[Andrii Nakryiko]

On non-SMP systems, there is no "per-CPU" data, it's just global data.
So in such case just don't do this_cpu_off-based per-CPU address adjustment.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404040951.d4CUx5S6-lkp@intel.com/
Fixes: 7bdbf7446305 ("bpf: add special internal-only MOV instruction to resolve per-CPU addrs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 arch/x86/net/bpf_jit_comp.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index af89dd117dce..964e8154da66 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1383,15 +1383,14 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
 				EMIT3(0x0F, 0x44, add_2reg(0xC0, AUX_REG, dst_reg));
 				break;
 			} else if (insn_is_mov_percpu_addr(insn)) {
-				u32 off = (u32)(unsigned long)&this_cpu_off;
-
 				/* mov <dst>, <src> (if necessary) */
 				EMIT_mov(dst_reg, src_reg);
-
+#ifdef CONFIG_SMP
 				/* add <dst>, gs:[<off>] */
 				EMIT2(0x65, add_1mod(0x48, dst_reg));
 				EMIT3(0x03, add_1reg(0x04, dst_reg), 0x25);
-				EMIT(off, 4);
+				EMIT((u32)(unsigned long)&this_cpu_off, 4);
+#endif
 				break;
 			}
 			fallthrough;
-- 
2.43.0

Re: [PATCH bpf-next] bpf: handle CONFIG_SMP=n configuration in x86 BPF JIT

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed,  3 Apr 2024 20:47:26 -0700 you wrote:
> On non-SMP systems, there is no "per-CPU" data, it's just global data.
> So in such case just don't do this_cpu_off-based per-CPU address adjustment.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202404040951.d4CUx5S6-lkp@intel.com/
> Fixes: 7bdbf7446305 ("bpf: add special internal-only MOV instruction to resolve per-CPU addrs")
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf: handle CONFIG_SMP=n configuration in x86 BPF JIT
    https://git.kernel.org/bpf/bpf-next/c/1e9e0b85255e

You are awesome, thank you!
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