Enable BTI in bionic linker
This patch adds support to load BTI-enabled objects.
According to the ABI, BTI is recorded in the .note.gnu.property section.
The new parser evaluates the property section, if exists.
It searches for .note section with NT_GNU_PROPERTY_TYPE_0.
Once found it tries to find GNU_PROPERTY_AARCH64_FEATURE_1_AND.
The results are cached.
The main change in linker is when protection of loaded ranges gets
applied. When BTI is requested and the platform also supports it
the prot flags have to be amended with PROT_BTI for executable ranges.
Failing to add PROT_BTI flag would disable BTI protection.
Moreover, adding the new PROT flag for shared objects without BTI
compatibility would break applications.
Kernel does not add PROT_BTI to a loaded ELF which has interpreter.
Linker handles this case too.
Test: 1. Flame boots
2. Tested on FVP with BTI enabled
Change-Id: Iafdf223b74c6e75d9f17ca90500e6fe42c4c1218
diff --git a/libc/include/bits/elf_arm64.h b/libc/include/bits/elf_arm64.h
index 6bb8384..9330d7b 100644
--- a/libc/include/bits/elf_arm64.h
+++ b/libc/include/bits/elf_arm64.h
@@ -89,4 +89,9 @@
#define R_AARCH64_TLSDESC 1031 /* 16-byte descriptor: resolver func + arg. */
#define R_AARCH64_IRELATIVE 1032
+/* Dynamic array tags */
+#define DT_AARCH64_BTI_PLT 0x70000001
+#define DT_AARCH64_PAC_PLT 0x70000003
+#define DT_AARCH64_VARIANT_PCS 0x70000005
+
#endif /* _AARCH64_ELF_MACHDEP_H_ */