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Message-Id: <20220418121211.667290215@linuxfoundation.org>
Date: Mon, 18 Apr 2022 14:12:20 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Alexei Starovoitov <ast@...nel.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 171/219] x86,bpf: Avoid IBT objtool warning
From: Peter Zijlstra <peterz@...radead.org>
[ Upstream commit be8a096521ca1a252bf078b347f96ce94582612e ]
Clang can inline emit_indirect_jump() and then folds constants, which
results in:
| vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x6a4: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40
| vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x67d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40
| vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x386: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20
| vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x35d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20
Suppress the optimization such that it must emit a code reference to
the __x86_indirect_thunk_array[] base.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Link: https://lkml.kernel.org/r/20220405075531.GB30877@worktop.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/x86/net/bpf_jit_comp.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 0ecb140864b2..b272e963388c 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -398,6 +398,7 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
EMIT_LFENCE();
EMIT2(0xFF, 0xE0 + reg);
} else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {
+ OPTIMIZER_HIDE_VAR(reg);
emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip);
} else
#endif
--
2.35.1
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