Messages in this thread Patch in this message | | | From | Zhen Lei <> | Subject | [PATCH 2/2] ARM: decompressor: relax the loading restriction of the decompressed kernel | Date | Mon, 28 Sep 2020 17:26:41 +0800 |
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mov r4, pc and r4, r4, #0xf8000000 //truncated to 128MiB boundary add r4, r4, #TEXT_OFFSET //PA(_start)
Currently, the decompressed kernel must be placed at the position: 128MiB boundary + TEXT_OFFSET. This limitation is just because we masked PC with 0xf80000000. Actually, we can directly obtain PA(_start) by using formula : VA(_start) + (PHYS_OFFSET - PAGE_OFFSET).
So the "PA(_start) - TEXT_OFFSET" can be 2MiB boundary, 1MiB boundary, and so on.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- arch/arm/boot/compressed/head.S | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 434a16982e344fe..e5ba2ad2ea4700f 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -255,26 +255,16 @@ not_angel: #ifdef CONFIG_AUTO_ZRELADDR /* - * Find the start of physical memory. As we are executing - * without the MMU on, we are in the physical address space. - * We just need to get rid of any offset by aligning the - * address. - * - * This alignment is a balance between the requirements of - * different platforms - we have chosen 128MB to allow - * platforms which align the start of their physical memory - * to 128MB to use this feature, while allowing the zImage - * to be placed within the first 128MB of memory on other - * platforms. Increasing the alignment means we place - * stricter alignment requirements on the start of physical - * memory, but relaxing it means that we break people who - * are already placing their zImage in (eg) the top 64MB - * of this range. + * Find ZRELADDR (Address where the decompressed kernel was + * placed, usually == PHYS_OFFSET + TEXT_OFFSET). That's the + * start physical address of the text section, PA(_start). + * As we are executing without the MMU on, we are in the + * physical address space. */ - mov r4, pc - and r4, r4, #0xf8000000 - /* Determine final kernel image address. */ - add r4, r4, #TEXT_OFFSET + adr r0, LC2 + ldmia r0, {r3-r4} + sub r3, r0, r3 @ PHYS_OFFSET - PAGE_OFFSET + add r4, r4, r3 @ PA(_start) #else ldr r4, =zreladdr #endif @@ -660,6 +650,11 @@ LC1: .word .L_user_stack_end - LC1 @ sp .word _edata - LC1 @ r6 .size LC1, . - LC1 + .align 2 + .type LC2, #object +LC2: .word LC2 + .word _start @ start VA of text section + .Lheadroom: .word _end - restart + 16384 + 1024*1024 -- 1.8.3
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