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Subject: Re: [edk2-devel] : Query regarding IsTextShdr inside Basetools
To: Laszlo Ersek <lersek@redhat.com>,
 "Liming Gao (Byosoft address)" <gaoliming@byosoft.com.cn>
Cc: devel@edk2.groups.io, mojha@codeaurora.org, discuss@edk2.groups.io
References: <dad12425-acbb-802e-3d76-2468fca67415@codeaurora.org>
 <9cd5c07e-d74d-5fa7-b3a7-2ef5fec01fc5@redhat.com>
 <7b920231-f763-06d6-c69c-a97123c7a4be@redhat.com>
From: "Ard Biesheuvel" <ard.biesheuvel@arm.com>
Message-ID: <086e1e01-7ab5-d877-480f-62f588b84300@arm.com>
Date: Thu, 12 Nov 2020 09:23:43 +0100
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On 11/11/20 11:41 PM, Laszlo Ersek wrote:
> On 11/11/20 23:40, Laszlo Ersek wrote:
>> Ard, Liming,
>>
>> can you please take a look?
>>
>> Thanks!
>> Laszlo
>=20
> Darn, I used Liming's old email address. Correcting it now. Sorry!
>=20
> Laszlo
>=20
>>
>> On 11/10/20 14:07, Mukesh Ojha wrote:
>>> Hi All,
>>>
>>> I have a doubt about the check we have put inside IsTextShdr() .
>>>
>>> STATIC
>>> BOOLEAN
>>> IsTextShdr (
>>>  =C2=A0 Elf_Shdr *Shdr
>>>  =C2=A0 )
>>> {
>>>  =C2=A0 return (BOOLEAN) ((Shdr->sh_flags & (SHF_WRITE | SHF_ALLOC)) =
=3D=3D
>>> SHF_ALLOC);
>>> }
>>>
>>>
>>> We are observing one issue where while generate EFI using GenFW in ED=
K2
>>> because test/data section offset is different than calculated
>>> mCoffSectionsOffset when scanning sections.
>>> I run GenFW with a failure dll in my local after adding some logs int=
o
>>> GenFW. and found that =E2=80=9CmCoffSectionsOffset=E2=80=9D for data =
section seems not
>>> to have expected value due to
>>> =E2=80=9C.note.gnu.property=E2=80=9D size. Because compiled dll has =E2=
=80=9C.note.gnu.property=E2=80=9D
>>> section with alloc flag and GenFW thinks that it=E2=80=99s a text sec=
tion if
>>> alloc flag is set.
>>> So its size is added to the mCoffSectionsOffset.
>>>
>>> Could you please give us an advice whether we can fix IsTextShdr()
>>> function like below ?
>>>
>>>
>>> --- a/BaseTools/Source/C/GenFw/Elf64Convert.c
>>> +++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
>>> @@ -229,7 +229,7 @@ IsTextShdr (
>>>  =C2=A0=C2=A0 Elf_Shdr *Shdr
>>>  =C2=A0=C2=A0 )
>>> {
>>> -=C2=A0 return (BOOLEAN) ((Shdr->sh_flags & (SHF_WRITE | SHF_ALLOC)) =
=3D=3D
>>> SHF_ALLOC);
>>> +=C2=A0 return (BOOLEAN) ((Shdr->sh_flags & (SHF_EXECINSTR | SHF_WRIT=
E |
>>> SHF_ALLOC)) =3D=3D (SHF_ALLOC | SHF_EXECINSTR));^
>>>


Was this ELF executable built using the GccBase.lds linker script? If=20
so, we should fix it to disregard .note sections.

If you are not using GccBase.lds, I'm afraid you are simply in=20
unsupported territory - there are too many assumptions in GenFw that are=20
not guaranteed to hold for arbitrary ELF executables.

I don't think changing IsTextShdr() is the right approach here.