[PATCH v5 04/36] x86/boot: Add .text.* to setup.ld

Kees Cook
2020-07-31T23:07:48Z

From: Arvind Sankar <nivedita@alum.mit.edu>

gcc puts the main function into .text.startup when compiled with -Os (or
-O2). This results in arch/x86/boot/main.c having a .text.startup
section which is currently not included explicitly in the linker script
setup.ld in the same directory.

The BFD linker places this orphan section immediately after .text, so
this still works. However, LLD git, since [1], is choosing to place it
immediately after the .bstext section instead (this is the first code
section). This plays havoc with the section layout that setup.elf
requires to create the setup header, for eg on 64-bit:

LD arch/x86/boot/setup.elf
ld.lld: error: section .text.startup file range overlaps with .header
>>> .text.startup range is [0x200040, 0x2001FE]
>>> .header range is [0x2001EF, 0x20026B]

ld.lld: error: section .header file range overlaps with .bsdata
>>> .header range is [0x2001EF, 0x20026B]
>>> .bsdata range is [0x2001FF, 0x200398]

ld.lld: error: section .bsdata file range overlaps with .entrytext
>>> .bsdata range is [0x2001FF, 0x200398]
>>> .entrytext range is [0x20026C, 0x2002D3]

ld.lld: error: section .text.startup virtual address range overlaps
with .header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]

ld.lld: error: section .header virtual address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]

ld.lld: error: section .bsdata virtual address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]

ld.lld: error: section .text.startup load address range overlaps with
.header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]

ld.lld: error: section .header load address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]

ld.lld: error: section .bsdata load address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]

Add .text.* to the .text output section to fix this, and also prevent
any future surprises if the compiler decides to create other such
sections.

[1] https://reviews.llvm.org/D75225

Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/setup.ld | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
index 24c95522f231..49546c247ae2 100644
--- a/arch/x86/boot/setup.ld
+++ b/arch/x86/boot/setup.ld
@@ -20,7 +20,7 @@ SECTIONS
.initdata : { *(.initdata) }
__end_init = .;

- .text : { *(.text) }
+ .text : { *(.text .text.*) }
.text32 : { *(.text32) }

. = ALIGN(16);
--
2.25.1