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arm64: cover the .head.text section in the .text segment mapping

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Keeping .head.text out of the .text mapping buys us very little: its actual
payload is only 4 KB, most of which is padding, but the page alignment may
add up to 2 MB (in case of CONFIG_DEBUG_ALIGN_RODATA=y) of additional
padding to the uncompressed kernel Image.

Also, on 4 KB granule kernels, the 4 KB misalignment of .text forces us to
map the adjacent 56 KB of code without the PTE_CONT attribute, and since
this region contains things like the vector table and the GIC interrupt
handling entry point, this region is likely to benefit from the reduced TLB
pressure that results from PTE_CONT mappings.

So remove the alignment between the .head.text and .text sections, and use
the [_text, _etext) rather than the [_stext, _etext) interval for mapping
the .text segment.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Ard Biesheuvel
2016-03-30 17:43:08 +02:00
committed by Will Deacon
parent 546c8c44f0
commit 7eb90f2ff7
2 changed files with 5 additions and 6 deletions
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arch/arm64/kernel/vmlinux.lds.S
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@@ -96,7 +96,6 @@ SECTIONS
_text = .;
HEAD_TEXT
}
ALIGN_DEBUG_RO_MIN(PAGE_SIZE)
.text : { /* Real text segment */
_stext = .; /* Text and read-only data */
__exception_text_start = .;