[edk2-devel] [PATCH v2 13/17] BaseTools/GenFw: Parse IBT/BTI support status from ELF note

[Ard Biesheuvel]

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 at kernel.org>
---
 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. */
-- 
2.39.2



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