Re: [PATCH bpf-next v9 4/5] bpf, x86: Emit ENDBR for indirect jump targets
From: Leon Hwang <hidden>
Date: 2026-03-14 13:35:42
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On 2026/3/14 14:48, Xu Kuohai wrote:
On 3/13/2026 6:15 PM, Leon Hwang wrote:quoted
quoted
+#ifdef CONFIG_X86_KERNEL_IBT + if (bpf_insn_is_indirect_target(env, bpf_prog, i - 1)) + EMIT_ENDBR(); +#endifNIT: is this CONFIG check necessary? EMIT_ENDBR already checks it. #ifdef CONFIG_X86_KERNEL_IBT #define EMIT_ENDBR() EMIT(gen_endbr(), 4) #define EMIT_ENDBR_POISON() EMIT(gen_endbr_poison(), 4) #else #define EMIT_ENDBR() #define EMIT_ENDBR_POISON() #endifWell, the code was originally written exactly without the #ifdef, but it triggered -Wempty-body warning: https://lore.kernel.org/bpf/202603051414.AAMjmOHv- lkp@intel.com/.
Let's update the macros instead, which can avoid the build warning and
get rid of the CONFIG check as well.
#define EMIT_ENDBR() do { } while (0)
#define EMIT_ENDBR_POISON() do { } while (0)
The way of "do { } while (0)" is commonly used in kernel.
Thanks,
Leon