Messages in this thread | | | Subject | Re: [PATCH] x86/alternative: fix undefined reference to __ibt_endbr_seal[_end] | From | Miaohe Lin <> | Date | Tue, 11 Oct 2022 10:26:38 +0800 |
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On 2022/10/9 21:11, Peter Zijlstra wrote: > On Sun, Oct 09, 2022 at 08:44:26PM +0800, Miaohe Lin wrote: >> On 2022/10/9 20:28, Peter Zijlstra wrote: >>> On Sun, Oct 09, 2022 at 11:45:32PM +0800, Miaohe Lin wrote: >>>> When I compile the kernel bzImage, there are several compile errors: >>>> >>>> ld: arch/x86/kernel/alternative.o: in function >>>> `alternative_instructions': >>>> alternative.c:(.init.text+0x15d): undefined reference to >>>> `__ibt_endbr_seal_end' >>>> ld: alternative.c:(.init.text+0x164): undefined reference to >>>> `__ibt_endbr_seal' >>>> >>>> It's because __ibt_endbr_seal and __ibt_endbr_seal_end are not optimized >>>> away when CONFIG_X86_KERNEL_IBT isn't enabled. Remove noinline attribute >>>> to help gcc optimize them away. >>>> >>>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> >>>> --- >>>> arch/x86/kernel/alternative.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c >>>> index 5cadcea035e0..beaf9fc44e2f 100644 >>>> --- a/arch/x86/kernel/alternative.c >>>> +++ b/arch/x86/kernel/alternative.c >>>> @@ -624,7 +624,7 @@ void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) >>>> >>>> #else >>>> >>>> -void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) { } >>>> +void __init_or_module apply_ibt_endbr(s32 *start, s32 *end) { } >>>> >>>> #endif /* CONFIG_X86_KERNEL_IBT */ >>>> >>> >>> None of this makes any sense... >> >> This compile error occurs in my env when CONFIG_X86_KERNEL_IBT isn't >> enabled with gcc version 7.3.0 (GCC). > > *sigh*... geriatric GCC :/
Yes, a geriatric GCC problem. :(
> > Anyway; perhaps clarify the changelog to state something like: > > Due to the explicit 'noinline' GCC-7.3 is not able to optimize away the > argument setup of: > > apply_ibt_endbr(__ibt_endbr_seal, __ibt_enbr_seal_end); > > even when X86_KERNEL_IBT=n and the function is an empty stub -- leading > to link errors due to missing __ibt_endbr_seal* symbols.
Will do it in v2. Thanks for your suggestion and comment.
Thanks, Miaohe Lin
> > > . >
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