From: Kees Cook keescook@chromium.org
[ Upstream commit 90776dd1c427cbb4d381aa4b13338f1fb1d20f5e ]
It seems that LLVM's linker does not correctly handle variable assignments involving section positions that are updated during the SECTIONS parsing. Commit aa69fb62bea1 ("arm64/efi: Mark __efistub_stext_offset as an absolute symbol explicitly") ran into this too, but found a different workaround.
However, this was not enough, as other variables were also miscalculated which manifested as boot failures under UEFI where __efistub__end was not taking the correct _end value (they should be the same):
$ ld.lld -EL -maarch64elf --no-undefined -X -shared \ -Bsymbolic -z notext -z norelro --no-apply-dynamic-relocs \ -o vmlinux.lld -T poc.lds --whole-archive vmlinux.o && \ readelf -Ws vmlinux.lld | egrep '\b(__efistub_|)_end\b' 368272: ffff000002218000 0 NOTYPE LOCAL HIDDEN 38 __efistub__end 368322: ffff000012318000 0 NOTYPE GLOBAL DEFAULT 38 _end
$ aarch64-linux-gnu-ld.bfd -EL -maarch64elf --no-undefined -X -shared \ -Bsymbolic -z notext -z norelro --no-apply-dynamic-relocs \ -o vmlinux.bfd -T poc.lds --whole-archive vmlinux.o && \ readelf -Ws vmlinux.bfd | egrep '\b(__efistub_|)_end\b' 338124: ffff000012318000 0 NOTYPE LOCAL DEFAULT ABS __efistub__end 383812: ffff000012318000 0 NOTYPE GLOBAL DEFAULT 15325 _end
To work around this, all of the __efistub_-prefixed variable assignments need to be moved after the linker script's SECTIONS entry. As it turns out, this also solves the problem fixed in commit aa69fb62bea1, so those changes are reverted here.
Link: https://github.com/ClangBuiltLinux/linux/issues/634 Link: https://bugs.llvm.org/show_bug.cgi?id=42990 Acked-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/image-vars.h | 51 +++++++++++++++++++++++++++++++++ arch/arm64/kernel/image.h | 42 --------------------------- arch/arm64/kernel/vmlinux.lds.S | 2 ++ 3 files changed, 53 insertions(+), 42 deletions(-) create mode 100644 arch/arm64/kernel/image-vars.h
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h new file mode 100644 index 0000000000000..25a2a9b479c2f --- /dev/null +++ b/arch/arm64/kernel/image-vars.h @@ -0,0 +1,51 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Linker script variables to be set after section resolution, as + * ld.lld does not like variables assigned before SECTIONS is processed. + */ +#ifndef __ARM64_KERNEL_IMAGE_VARS_H +#define __ARM64_KERNEL_IMAGE_VARS_H + +#ifndef LINKER_SCRIPT +#error This file should only be included in vmlinux.lds.S +#endif + +#ifdef CONFIG_EFI + +__efistub_stext_offset = stext - _text; + +/* + * The EFI stub has its own symbol namespace prefixed by __efistub_, to + * isolate it from the kernel proper. The following symbols are legally + * accessed by the stub, so provide some aliases to make them accessible. + * Only include data symbols here, or text symbols of functions that are + * guaranteed to be safe when executed at another offset than they were + * linked at. The routines below are all implemented in assembler in a + * position independent manner + */ +__efistub_memcmp = __pi_memcmp; +__efistub_memchr = __pi_memchr; +__efistub_memcpy = __pi_memcpy; +__efistub_memmove = __pi_memmove; +__efistub_memset = __pi_memset; +__efistub_strlen = __pi_strlen; +__efistub_strnlen = __pi_strnlen; +__efistub_strcmp = __pi_strcmp; +__efistub_strncmp = __pi_strncmp; +__efistub_strrchr = __pi_strrchr; +__efistub___flush_dcache_area = __pi___flush_dcache_area; + +#ifdef CONFIG_KASAN +__efistub___memcpy = __pi_memcpy; +__efistub___memmove = __pi_memmove; +__efistub___memset = __pi_memset; +#endif + +__efistub__text = _text; +__efistub__end = _end; +__efistub__edata = _edata; +__efistub_screen_info = screen_info; + +#endif + +#endif /* __ARM64_KERNEL_IMAGE_VARS_H */ diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h index 2b85c0d6fa3d1..c7d38c660372c 100644 --- a/arch/arm64/kernel/image.h +++ b/arch/arm64/kernel/image.h @@ -65,46 +65,4 @@ DEFINE_IMAGE_LE64(_kernel_offset_le, TEXT_OFFSET); \ DEFINE_IMAGE_LE64(_kernel_flags_le, __HEAD_FLAGS);
-#ifdef CONFIG_EFI - -/* - * Use ABSOLUTE() to avoid ld.lld treating this as a relative symbol: - * https://github.com/ClangBuiltLinux/linux/issues/561 - */ -__efistub_stext_offset = ABSOLUTE(stext - _text); - -/* - * The EFI stub has its own symbol namespace prefixed by __efistub_, to - * isolate it from the kernel proper. The following symbols are legally - * accessed by the stub, so provide some aliases to make them accessible. - * Only include data symbols here, or text symbols of functions that are - * guaranteed to be safe when executed at another offset than they were - * linked at. The routines below are all implemented in assembler in a - * position independent manner - */ -__efistub_memcmp = __pi_memcmp; -__efistub_memchr = __pi_memchr; -__efistub_memcpy = __pi_memcpy; -__efistub_memmove = __pi_memmove; -__efistub_memset = __pi_memset; -__efistub_strlen = __pi_strlen; -__efistub_strnlen = __pi_strnlen; -__efistub_strcmp = __pi_strcmp; -__efistub_strncmp = __pi_strncmp; -__efistub_strrchr = __pi_strrchr; -__efistub___flush_dcache_area = __pi___flush_dcache_area; - -#ifdef CONFIG_KASAN -__efistub___memcpy = __pi_memcpy; -__efistub___memmove = __pi_memmove; -__efistub___memset = __pi_memset; -#endif - -__efistub__text = _text; -__efistub__end = _end; -__efistub__edata = _edata; -__efistub_screen_info = screen_info; - -#endif - #endif /* __ARM64_KERNEL_IMAGE_H */ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 7fa0083749078..803b24d2464ae 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -245,6 +245,8 @@ SECTIONS HEAD_SYMBOLS }
+#include "image-vars.h" + /* * The HYP init code and ID map text can't be longer than a page each, * and should not cross a page boundary.