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authorArd Biesheuvel <ardb@kernel.org>2020-11-17 13:47:27 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2020-11-17 16:14:20 +0000
commite2a073dde9218cdef3c5431bddabf4549dd65fea (patch)
tree979aa59ce9533be065c22f316c68346783f5e4d4 /arch/arm64/kernel/vmlinux.lds.S
parentf8394f232b1eab649ce2df5c5f15b0e528c92091 (diff)
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arm64: omit [_text, _stext) from permanent kernel mapping
In a previous patch, we increased the size of the EFI PE/COFF header to 64 KB, which resulted in the _stext symbol to appear at a fixed offset of 64 KB into the image. Since 64 KB is also the largest page size we support, this completely removes the need to map the first 64 KB of the kernel image, given that it only contains the arm64 Image header and the EFI header, neither of which we ever access again after booting the kernel. More importantly, we should avoid an executable mapping of non-executable and not entirely predictable data, to deal with the unlikely event that we inadvertently emitted something that looks like an opcode that could be used as a gadget for speculative execution. So let's limit the kernel mapping of .text to the [_stext, _etext) region, which matches the view of generic code (such as kallsyms) when it reasons about the boundaries of the kernel's .text section. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20201117124729.12642-2-ardb@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel/vmlinux.lds.S')
-rw-r--r--arch/arm64/kernel/vmlinux.lds.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 1bda604f4c70..48b222f1c700 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -121,7 +121,7 @@ SECTIONS
_text = .;
HEAD_TEXT
}
- .text : { /* Real text segment */
+ .text : ALIGN(SEGMENT_ALIGN) { /* Real text segment */
_stext = .; /* Text and read-only data */
IRQENTRY_TEXT
SOFTIRQENTRY_TEXT