linux-kernel - [PATCH] bpf: x86: avoid link error with CONFIG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Thu,  4 Apr 2024 14:33:25 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	John Fastabend <john.fastabend@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	Menglong Dong <imagedong@...cent.com>,
	Leon Hwang <hffilwlqm@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] bpf: x86: avoid link error with CONFIG_SMP=n

From: Arnd Bergmann <arnd@...db.de>

On UP systems, this_cpu_off is not defined, so the new percpu code in bpf
fails to link:

x86_64-linux-ld: vmlinux.o: in function `do_jit':
bpf_jit_comp.c:(.text+0xbab14): undefined reference to `this_cpu_off'

Use offset zero on UP builds instead.

Fixes: 7bdbf7446305 ("bpf: add special internal-only MOV instruction to resolve per-CPU addrs")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
I assume this is not the correct fix, or at least not the best one, so
please treat this as a bug report. It does address the link failure for
me, so I applied this to my randconfig build tree.
---
 arch/x86/net/bpf_jit_comp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index d6ebb9136f3c..8b8eebb89a9b 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1383,7 +1383,10 @@ 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;
+				u32 off = 0;
+
+				if (IS_ENABLED(CONFIG_SMP))
+					off = (u32)(unsigned long)&this_cpu_off;
 
 				/* mov <dst>, <src> (if necessary) */
 				EMIT_mov(dst_reg, src_reg);
-- 
2.39.2