[edk2-devel] [RFT PATCH v2 2/6] BaseTools/tools_def CLANGDWARF: Permit text relocations

[Ard Biesheuvel]

We rely on PIE executables to get the codegen that is suitable for
PE/COFF conversion where the resulting executables can be loaded
anywhere in the address space.

However, ELF linkers may default to disallowing text relocations in PIE
executables, as this would require text segments to be updated at
runtime, which is bad for security and increases the copy-on-write
footprint of ELF executables and shared libraries.

However, none of those concerns apply to PE/COFF executables in the
context of EFI, which are copied into memory rather than mmap()'ed, and
fixed up by the loader before launch.

So pass -z notext to the LLD linker to permit runtime relocations in
read-only sections.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 BaseTools/Conf/tools_def.template | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index 1855f1038b1571e4..0c6fc4a3011c8d5c 100755
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -2870,7 +2870,7 @@ DEFINE CLANGDWARF_X64_PREFIX        = ENV(CLANG_BIN)
 DEFINE CLANGDWARF_IA32_X64_DLINK_COMMON   = -nostdlib -Wl,-q,--gc-sections -z max-page-size=0x40
 DEFINE CLANGDWARF_DLINK2_FLAGS_COMMON     = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/ClangBase.lds
 DEFINE CLANGDWARF_IA32_X64_ASLDLINK_FLAGS = DEF(CLANGDWARF_IA32_X64_DLINK_COMMON) -Wl,--defsym=PECOFF_HEADER_SIZE=0 DEF(CLANGDWARF_DLINK2_FLAGS_COMMON) -Wl,--entry,ReferenceAcpiTable -u ReferenceAcpiTable
-DEFINE CLANGDWARF_IA32_X64_DLINK_FLAGS    = DEF(CLANGDWARF_IA32_X64_DLINK_COMMON) -Wl,--entry,$(IMAGE_ENTRY_POINT) -u $(IMAGE_ENTRY_POINT) -Wl,-Map,$(DEST_DIR_DEBUG)/$(BASE_NAME).map,--whole-archive
+DEFINE CLANGDWARF_IA32_X64_DLINK_FLAGS    = DEF(CLANGDWARF_IA32_X64_DLINK_COMMON) -Wl,--entry,$(IMAGE_ENTRY_POINT) -u $(IMAGE_ENTRY_POINT) -Wl,-Map,$(DEST_DIR_DEBUG)/$(BASE_NAME).map,--whole-archive -Wl,-z,notext
 DEFINE CLANGDWARF_IA32_DLINK2_FLAGS       = -Wl,--defsym=PECOFF_HEADER_SIZE=0x220 DEF(CLANGDWARF_DLINK2_FLAGS_COMMON)
 DEFINE CLANGDWARF_X64_DLINK2_FLAGS        = -Wl,--defsym=PECOFF_HEADER_SIZE=0x228 DEF(CLANGDWARF_DLINK2_FLAGS_COMMON)
 
-- 
2.39.2



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