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Date:   Thu, 24 Nov 2022 12:31:31 +0000
From:   Vincent Donnefort <vdonnefort@google.com>
To:     llvm@lists.linux.dev, linux-kernel@vger.kernel.org
Cc:     samitolvanen@google.com, nhuck@google.com, ndesaulniers@google.com,
        kernel-team@android.com
Subject: Bug: MODPOST mismatch ignored due to LTO
Message-ID: <Y39kI3MOtVI5BAnV@google.com>
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Hi all,

It seems that enabling LTO breaks the check for section mismatch in modpost.

If I create on purpose a mismatch here's the output without LTO

check_section_mismatch()
  fromsec=.text
  tosec=.init.text
  sym=kvm_arch_vcpu_create

=> section mismatch in reference: kvm_vm_ioctl_create_vcpu (section: .text) -> kvm_arch_vcpu_create (section: .init.text)

While with LTO:

check_section_mismatch()
  fromsec=.text.kvm_vm_ioctl_create_vcpu 
  tosec=.init.text
  sym=kvm_arch_vcpu_create

=> mismatch ignored, the section ".text.kvm_vm_ioctl_create_vcpu" is
unsurprisingly unknown

LTO seems to append the symbol name to the section which is a problem for
modpost.

Is that a known issue?

Thanks,
Vincent