Re: [PATCH v2 mips-next 3/4] MIPS: vmlinux.lds.S: catch bad .got, .plt and .rel.dyn at link time

2021-01-06 Thread Alexander Lobakin 
From: Nathan Chancellor 
Date: Wed, 6 Jan 2021 13:23:24 -0700

On Wed, Jan 06, 2021 at 08:08:29PM +, Alexander Lobakin wrote:
>> Catch any symbols placed in .got, .got.plt, .plt, .rel.dyn
>> or .rela.dyn and check for these sections to be zero-sized
>> at link time.
>>
>> At least two of them were noticed in real builds:
>>
>> mips-alpine-linux-musl-ld: warning: orphan section `.rel.dyn'
>> from `init/main.o' being placed in section `.rel.dyn'
>>
>> ld.lld: warning: :(.got) is being placed in '.got'
>>
>> Adopted from x86/kernel/vmlinux.lds.S.
>>
>> Reported-by: Nathan Chancellor  # .got
>> Suggested-by: Fangrui Song  # .rel.dyn
>> Signed-off-by: Alexander Lobakin 
>> ---
>>  arch/mips/kernel/vmlinux.lds.S | 35 ++
>>  1 file changed, 35 insertions(+)
>>
>> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
>> index 5d6563970ab2..05eda9d9a7d5 100644
>> --- a/arch/mips/kernel/vmlinux.lds.S
>> +++ b/arch/mips/kernel/vmlinux.lds.S
>> @@ -227,4 +227,39 @@ SECTIONS
>>  *(.pdr)
>>  *(.reginfo)
>>  }
>> +
>> +/*
>> + * Sections that should stay zero sized, which is safer to
>> + * explicitly check instead of blindly discarding.
>> + */
>> +
>> +.got : {
>> +*(.got)
>> +*(.igot.*)
>> +}
>> +ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
>
> This assertion does trigger now.
>
> $ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- LLVM=1 \
>O=out/mipsel distclean malta_kvm_guest_defconfig all
> ...
> ld.lld: error: Unexpected GOT entries detected!
> ld.lld: error: Unexpected GOT entries detected!
> ...

Oops. I'll build my kernel with LLVM stack and dig into it deeper
tomorrow.

>> +.got.plt (INFO) : {
>> +*(.got.plt)
>> +}
>> +ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
>> +
>> +.plt : {
>> +*(.plt)
>> +*(.plt.*)
>> +*(.iplt)
>> +}
>> +ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages 
>> detected!")
>> +
>> +.rel.dyn : {
>> +*(.rel.*)
>> +*(.rel_*)
>> +}
>> +ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) 
>> detected!")
>> +
>> +.rela.dyn : {
>> +*(.rela.*)
>> +*(.rela_*)
>> +}
>> +ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) 
>> detected!")
>>  }
>> --
>> 2.30.0

Thanks,
Al

Re: [PATCH v2 mips-next 3/4] MIPS: vmlinux.lds.S: catch bad .got, .plt and .rel.dyn at link time

2021-01-06 Thread Nathan Chancellor 
On Wed, Jan 06, 2021 at 08:08:29PM +, Alexander Lobakin wrote:
> Catch any symbols placed in .got, .got.plt, .plt, .rel.dyn
> or .rela.dyn and check for these sections to be zero-sized
> at link time.
> 
> At least two of them were noticed in real builds:
> 
> mips-alpine-linux-musl-ld: warning: orphan section `.rel.dyn'
> from `init/main.o' being placed in section `.rel.dyn'
> 
> ld.lld: warning: :(.got) is being placed in '.got'
> 
> Adopted from x86/kernel/vmlinux.lds.S.
> 
> Reported-by: Nathan Chancellor  # .got
> Suggested-by: Fangrui Song  # .rel.dyn
> Signed-off-by: Alexander Lobakin 
> ---
>  arch/mips/kernel/vmlinux.lds.S | 35 ++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index 5d6563970ab2..05eda9d9a7d5 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -227,4 +227,39 @@ SECTIONS
>   *(.pdr)
>   *(.reginfo)
>   }
> +
> + /*
> +  * Sections that should stay zero sized, which is safer to
> +  * explicitly check instead of blindly discarding.
> +  */
> +
> + .got : {
> + *(.got)
> + *(.igot.*)
> + }
> + ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")

This assertion does trigger now.

$ make -skj"$(nproc)" ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- LLVM=1 \
   O=out/mipsel distclean malta_kvm_guest_defconfig all
...
ld.lld: error: Unexpected GOT entries detected!
ld.lld: error: Unexpected GOT entries detected!
...

> + .got.plt (INFO) : {
> + *(.got.plt)
> + }
> + ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
> +
> + .plt : {
> + *(.plt)
> + *(.plt.*)
> + *(.iplt)
> + }
> + ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages 
> detected!")
> +
> + .rel.dyn : {
> + *(.rel.*)
> + *(.rel_*)
> + }
> + ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) 
> detected!")
> +
> + .rela.dyn : {
> + *(.rela.*)
> + *(.rela_*)
> + }
> + ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) 
> detected!")
>  }
> -- 
> 2.30.0
> 
>

Re: [PATCH v2 mips-next 3/4] MIPS: vmlinux.lds.S: catch bad .got, .plt and .rel.dyn at link time

2021-01-06 Thread Fāng-ruì Sòng 
On Wed, Jan 6, 2021 at 12:08 PM Alexander Lobakin  wrote:
>
> Catch any symbols placed in .got, .got.plt, .plt, .rel.dyn
> or .rela.dyn and check for these sections to be zero-sized
> at link time.
>
> At least two of them were noticed in real builds:
>
> mips-alpine-linux-musl-ld: warning: orphan section `.rel.dyn'
> from `init/main.o' being placed in section `.rel.dyn'
>
> ld.lld: warning: :(.got) is being placed in '.got'
>
> Adopted from x86/kernel/vmlinux.lds.S.
>
> Reported-by: Nathan Chancellor  # .got
> Suggested-by: Fangrui Song  # .rel.dyn
> Signed-off-by: Alexander Lobakin 
> ---
>  arch/mips/kernel/vmlinux.lds.S | 35 ++
>  1 file changed, 35 insertions(+)
>
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index 5d6563970ab2..05eda9d9a7d5 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -227,4 +227,39 @@ SECTIONS
> *(.pdr)
> *(.reginfo)
> }
> +
> +   /*
> +* Sections that should stay zero sized, which is safer to
> +* explicitly check instead of blindly discarding.
> +*/
> +
> +   .got : {
> +   *(.got)
> +   *(.igot.*)
> +   }
> +   ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
> +
> +   .got.plt (INFO) : {
> +   *(.got.plt)
> +   }
> +   ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")

(INFO) drops the SHF_ALLOC flag from the output section (It does not
mean "informational"). INFO is not need here.
The diff from 815d680771ae09080d2da83dac2647c08cdf99ce "x86/build:
Enforce an empty .got.plt section" is not needed.

> +   .plt : {
> +   *(.plt)
> +   *(.plt.*)
> +   *(.iplt)
> +   }
> +   ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages 
> detected!")
> +
> +   .rel.dyn : {
> +   *(.rel.*)
> +   *(.rel_*)
> +   }
> +   ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) 
> detected!")
> +
> +   .rela.dyn : {
> +   *(.rela.*)
> +   *(.rela_*)
> +   }
> +   ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations 
> (.rela) detected!")
>  }

x86 has both .rel.dyn and .rela.dyn because i386 psABI uses REL while
x86-64 psABI uses RELA, but mips does not need .rela.dyn

> --
> 2.30.0
>
>

[PATCH v2 mips-next 3/4] MIPS: vmlinux.lds.S: catch bad .got, .plt and .rel.dyn at link time

2021-01-06 Thread Alexander Lobakin 
Catch any symbols placed in .got, .got.plt, .plt, .rel.dyn
or .rela.dyn and check for these sections to be zero-sized
at link time.

At least two of them were noticed in real builds:

mips-alpine-linux-musl-ld: warning: orphan section `.rel.dyn'
from `init/main.o' being placed in section `.rel.dyn'

ld.lld: warning: :(.got) is being placed in '.got'

Adopted from x86/kernel/vmlinux.lds.S.

Reported-by: Nathan Chancellor  # .got
Suggested-by: Fangrui Song  # .rel.dyn
Signed-off-by: Alexander Lobakin 
---
 arch/mips/kernel/vmlinux.lds.S | 35 ++
 1 file changed, 35 insertions(+)

diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 5d6563970ab2..05eda9d9a7d5 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -227,4 +227,39 @@ SECTIONS
*(.pdr)
*(.reginfo)
}
+
+   /*
+* Sections that should stay zero sized, which is safer to
+* explicitly check instead of blindly discarding.
+*/
+
+   .got : {
+   *(.got)
+   *(.igot.*)
+   }
+   ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
+
+   .got.plt (INFO) : {
+   *(.got.plt)
+   }
+   ASSERT(SIZEOF(.got.plt) == 0, "Unexpected GOT/PLT entries detected!")
+
+   .plt : {
+   *(.plt)
+   *(.plt.*)
+   *(.iplt)
+   }
+   ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages 
detected!")
+
+   .rel.dyn : {
+   *(.rel.*)
+   *(.rel_*)
+   }
+   ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) 
detected!")
+
+   .rela.dyn : {
+   *(.rela.*)
+   *(.rela_*)
+   }
+   ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) 
detected!")
 }
-- 
2.30.0