Re: [PATCH bpf 1/2] x86/ftrace: Use jmp mode only where functions are aligned

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Sat, Oct 24, 2026 at 12:37 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> Bit 0 has that meaning only for the direct trampolines that a dyn_ftrace
> record can point to, so jmp mode relies on every other target being even.
> Select HAVE_DYNAMIC_FTRACE_WITH_JMP only where it is, with
> CONFIG_CC_HAS_SANE_FUNCTION_ALIGNMENT or without CONFIG_CC_OPTIMIZE_FOR_SIZE.

Disabling it for -Os builds is not great.
Can we fix the users of ftrace_call_replace() instead ?

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 17d6edf..654c3f2 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -190,11 +190,11 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	const char *new;

 	ip = (unsigned long)(&ftrace_call);
-	new = ftrace_call_replace(ip, (unsigned long)func);
+	new = text_gen_insn(CALL_INSN_OPCODE, (void *)ip, func);
 	smp_text_poke_single((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

 	ip = (unsigned long)(&ftrace_regs_call);
-	new = ftrace_call_replace(ip, (unsigned long)func);
+	new = text_gen_insn(CALL_INSN_OPCODE, (void *)ip, func);
 	smp_text_poke_single((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

 	return 0;
@@ -503,7 +503,7 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)

 	mutex_lock(&text_mutex);
 	/* Do a safe modify in case the trampoline is executing */
-	new = ftrace_call_replace(ip, (unsigned long)func);
+	new = text_gen_insn(CALL_INSN_OPCODE, (void *)ip, func);
 	smp_text_poke_single((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
 	mutex_unlock(&text_mutex);
 }