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Message-ID: <9401cd23-134c-b9fd-6c33-306510ed7cb0@linux.microsoft.com>
Date: Tue, 4 Apr 2023 21:57:44 -0400
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Subject: Re: [edk2-devel] [PATCH v3 1/4] BaseTools/GenFw: Parse IBT/BTI support status from ELF note
To: devel@edk2.groups.io, ardb@kernel.org
Cc: Michael Kinney <michael.d.kinney@intel.com>,
 Liming Gao <gaoliming@byosoft.com.cn>, Jiewen Yao <jiewen.yao@intel.com>,
 Michael Kubacki <michael.kubacki@microsoft.com>,
 Sean Brogan <sean.brogan@microsoft.com>,
 Rebecca Cran <quic_rcran@quicinc.com>,
 Leif Lindholm <quic_llindhol@quicinc.com>,
 Sami Mujawar <sami.mujawar@arm.com>, Taylor Beebe <t@taylorbeebe.com>,
 =?UTF-8?Q?Marvin_H=c3=a4user?= <mhaeuser@posteo.de>,
 Bob Feng <bob.c.feng@intel.com>,
 Oliver Smith-Denny <osde@linux.microsoft.com>
References: <20230404154022.2776035-1-ardb@kernel.org>
 <20230404154022.2776035-2-ardb@kernel.org>
From: "Michael Kubacki" <mikuback@linux.microsoft.com>
In-Reply-To: <20230404154022.2776035-2-ardb@kernel.org>
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Acked-by: Michael Kubacki <michael.kubacki@microsoft.com>

On 4/4/2023 11:40 AM, Ard Biesheuvel wrote:
> When performing ELF to PE/COFF conversion, parse any notes sections to
> decide whether the image supports forward CFI landing pads. This will be
> used to set the associated DllCharacteristicsEx flag in a subsequent
> patch.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
> Reviewed-by: Oliver Smith-Denny <osde@linux.microsoft.com>
> ---
>   BaseTools/Source/C/GenFw/Elf64Convert.c | 50 ++++++++++++++++++++
>   BaseTools/Source/C/GenFw/elf_common.h   |  9 ++++
>   2 files changed, 59 insertions(+)
> 
> diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c b/BaseTools/Source/C/GenFw/Elf64Convert.c
> index 8b50774beb1eebda..2a810e835d4a4a66 100644
> --- a/BaseTools/Source/C/GenFw/Elf64Convert.c
> +++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
> @@ -770,6 +770,49 @@ WriteSectionRiscV64 (
>     }
> 
>   }
> 
>   
> 
> +STATIC UINT16 mDllCharacteristicsEx;
> 
> +
> 
> +STATIC
> 
> +VOID
> 
> +ParseNoteSection (
> 
> +  CONST Elf_Shdr  *Shdr
> 
> +  )
> 
> +{
> 
> +  CONST Elf_Note *Note;
> 
> +  CONST UINT32   *Prop;
> 
> +  UINT32         Prop0;
> 
> +  UINT32         Prop2;
> 
> +
> 
> +  Note = (Elf_Note *)((UINT8 *)mEhdr + Shdr->sh_offset);
> 
> +
> 
> +  if ((Note->n_type == NT_GNU_PROPERTY_TYPE_0) &&
> 
> +      (Note->n_namesz == sizeof ("GNU")) &&
> 
> +      (strcmp ((CHAR8 *)(Note + 1), "GNU") == 0) &&
> 
> +      (Note->n_descsz > sizeof (UINT32[2]))) {
> 
> +    Prop = (UINT32 *)((UINT8 *)(Note + 1) + sizeof("GNU"));
> 
> +
> 
> +    switch (mEhdr->e_machine) {
> 
> +    case EM_AARCH64:
> 
> +      Prop0 = GNU_PROPERTY_AARCH64_FEATURE_1_AND;
> 
> +      Prop2 = GNU_PROPERTY_AARCH64_FEATURE_1_BTI;
> 
> +      break;
> 
> +
> 
> +    case EM_X86_64:
> 
> +      Prop0 = GNU_PROPERTY_X86_FEATURE_1_AND;
> 
> +      Prop2 = GNU_PROPERTY_X86_FEATURE_1_IBT;
> 
> +      break;
> 
> +
> 
> +    default:
> 
> +      return;
> 
> +    }
> 
> +    if ((Prop[0] == Prop0) &&
> 
> +        (Prop[1] >= sizeof (UINT32)) &&
> 
> +        ((Prop[2] & Prop2) != 0)) {
> 
> +      mDllCharacteristicsEx |= EFI_IMAGE_DLLCHARACTERISTICS_EX_FORWARD_CFI_COMPAT;
> 
> +    }
> 
> +  }
> 
> +}
> 
> +
> 
>   //
> 
>   // Elf functions interface implementation
> 
>   //
> 
> @@ -826,6 +869,13 @@ ScanSections64 (
>       }
> 
>     }
> 
>   
> 
> +  for (i = 0; i < mEhdr->e_shnum; i++) {
> 
> +    Elf_Shdr *shdr = GetShdrByIndex(i);
> 
> +    if (shdr->sh_type == SHT_NOTE) {
> 
> +      ParseNoteSection (shdr);
> 
> +    }
> 
> +  }
> 
> +
> 
>     //
> 
>     // Check if mCoffAlignment is larger than MAX_COFF_ALIGNMENT
> 
>     //
> 
> diff --git a/BaseTools/Source/C/GenFw/elf_common.h b/BaseTools/Source/C/GenFw/elf_common.h
> index 7b7fdeb3290dfa88..ccd32804b090a226 100644
> --- a/BaseTools/Source/C/GenFw/elf_common.h
> +++ b/BaseTools/Source/C/GenFw/elf_common.h
> @@ -59,6 +59,15 @@ typedef struct {
>     UINT32  n_type;    /* Type of this note. */
> 
>   } Elf_Note;
> 
>   
> 
> +#define NT_GNU_PROPERTY_TYPE_0  5
> 
> +
> 
> +#define GNU_PROPERTY_X86_FEATURE_1_AND  0xc0000002
> 
> +#define GNU_PROPERTY_X86_FEATURE_1_IBT  0x1
> 
> +
> 
> +#define GNU_PROPERTY_AARCH64_FEATURE_1_AND  0xc0000000
> 
> +#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI  0x1
> 
> +#define GNU_PROPERTY_AARCH64_FEATURE_1_PAC  0x2
> 
> +
> 
>   /* Indexes into the e_ident array.  Keep synced with
> 
>      http://www.sco.com/developers/gabi/latest/ch4.eheader.html */
> 
>   #define EI_MAG0    0  /* Magic number, byte 0. */
>