Re: [PATCH] BaseTools: GCC: move most AutoGen.obj contents back to .data section

[Laszlo Ersek <lersek@redhat.com>]

On 02/24/17 04:20, Gao, Liming wrote:
> Reviewed-by: Liming Gao <liming.gao@intel.com>

Thank you both, pushed as 3cf41b8728a3.

Laszlo

> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] 
> Sent: Friday, February 24, 2017 6:29 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: edk2-devel@lists.01.org <edk2-devel@ml01.01.org>; Gao, Liming <liming.gao@intel.com>; Zhu, Yonghong <yonghong.zhu@intel.com>
> Subject: Re: [PATCH] BaseTools: GCC: move most AutoGen.obj contents back to .data section
> 
> On 23 February 2017 at 19:53, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 02/23/17 19:30, Ard Biesheuvel wrote:
>>> The generated AutoGen.c files mostly contain read-only data, but due to
>>> lacking annotations, all of it is emitted into the .data section by the
>>> compiler.
>>>
>>> Given that GUIDs are UEFI's gaffer tape, having writable GUIDs is a
>>> security hazard, and this was the main rationale for putting AutoGen.obj
>>> in the .text section. However, as it turns out, patchable PCDs are emitted
>>> there as well, which can legally be modified at runtime.
>>>
>>> So update the wildcard pattern to only match g...Guid sections, and move
>>> everything else back to .data (Note that this relies on -fdata-sections,
>>> without that option, everything is emitted into .data)
>>>
>>> Contributed-under: TianoCore Contribution Agreement 1.0
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> ---
>>>  BaseTools/Scripts/GccBase.lds | 9 ++++++---
>>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
>>> index 900848747144..41e5c0b4a769 100644
>>> --- a/BaseTools/Scripts/GccBase.lds
>>> +++ b/BaseTools/Scripts/GccBase.lds
>>> @@ -32,11 +32,14 @@ SECTIONS {
>>>      *(.got .got.*)
>>>
>>>      /*
>>> -     * The contents of AutoGen.c files are constant from the POV of the program,
>>> -     * but most of its contents end up in .data or .bss by default since few of
>>> +     * The contents of AutoGen.c files are mostly constant from the POV of the
>>> +     * program, but most of it ends up in .data or .bss by default since few of
>>>       * the variable definitions that get emitted are declared as CONST.
>>> +     * Unfortunately, we cannot pull it into the .text section entirely, since
>>> +     * patchable PCDs are also emitted here, but we can at least move all of the
>>> +     * emitted GUIDs here.
>>>       */
>>> -    *:AutoGen.obj(.data .data.* .bss .bss.*)
>>> +    *:AutoGen.obj(.data.g*Guid)
>>>    }
>>>
>>>    /*
>>>
>>
>> Do you agree to add:
>>
>> Fixes: 233bd25b000f92fc4bbe181fa48edcd72808de8e
>>
>> to the commit message, or to reference that commit in some other form?
>>
> 
> Yes, that makes sense.
> 
>> Either way:
>>
>> Tested-by: Laszlo Ersek <lersek@redhat.com>
>>
>> Thank you very much for the quick fix!
> 
> No problem.
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