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[ARM] 3809/3: get rid of 4 megabyte kernel image size limit

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We currently have a hardcoded 4 megabyte uncompressed kernel image
size limit, which is easily exceeded by, for example, enabling some of
the various kernel debugging options.

When setting up the initial page tables (which is where this 4M limit
is hardcoded), it's actually relatively easy to find out the true size
of the uncompressed kernel image and create enough page table entries
for things to fit, so this patch makes it so.

In the decompressor, we also need to know the size of the uncompressed
kernel image, to figure out whether there is any chance that uncompressing
the kernel might overwrite the compressed kernel image stored elsewhere
in memory. We don't have that info at this boot stage, though, so we
approximate the size of the uncompressed kernel by taking the compressed
kernel image size and allowing for a maximum 4x expansion.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Lennert Buytenhek 2006-09-29 21:14:05 +01:00 committed by Russell King
parent 6ae5a6ef03
commit 2552fc27ff
2 changed files with 11 additions and 10 deletions
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3
arch/arm/boot/compressed/head.S
View file

@ -237,7 +237,8 @@ not_relocated: mov r0, #0
*/
cmp r4, r2
bhs wont_overwrite
add r0, r4, #4096*1024 @ 4MB largest kernel size
sub r3, sp, r5 @ > compressed kernel size
add r0, r4, r3, lsl #2 @ allow for 4x expansion
cmp r0, r5
bls wont_overwrite

18
arch/arm/kernel/head.S
View file

@ -234,18 +234,18 @@ __create_page_tables:
/*
* Now setup the pagetables for our kernel direct
* mapped region. We round TEXTADDR down to the
* nearest megabyte boundary. It is assumed that
* the kernel fits within 4 contigous 1MB sections.
* mapped region.
*/
add r0, r4, #(TEXTADDR & 0xff000000) >> 18 @ start of kernel
str r3, [r0, #(TEXTADDR & 0x00f00000) >> 18]!
add r3, r3, #1 << 20
str r3, [r0, #4]! @ KERNEL + 1MB
add r3, r3, #1 << 20
str r3, [r0, #4]! @ KERNEL + 2MB
add r3, r3, #1 << 20
str r3, [r0, #4] @ KERNEL + 3MB
ldr r6, =(_end - PAGE_OFFSET - 1) @ r6 = number of sections
mov r6, r6, lsr #20 @ needed for kernel minus 1
1: add r3, r3, #1 << 20
str r3, [r0, #4]!
subs r6, r6, #1
bgt 1b
/*
* Then map first 1MB of ram in case it contains our boot params.