[PATCHv2] arm64/crashdump-arm64: deduce the paddr of _text

[PATCHv2] arm64/crashdump-arm64: deduce the paddr of _text

[Pingfan Liu]

Since kernel commit e2a073dde921 ("arm64: omit [_text, _stext) from
permanent kernel mapping"), the physical address of 'Kernel code' in
/proc/iomem is mapped from _text, instead, from _stext.

Taking the compatibility into account, it had better deduce the paddr of
_text despite of the unavailability through /proc/iomem. It can be
achieved by utilizing the fact _text aligned on 2MB.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Simon Horman <horms@verge.net.au>
To: kexec@lists.infradead.org
---
v1 -> v2:
 deduce paddr of _text to cope with compability.

 kexec/arch/arm64/crashdump-arm64.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
index 38d1a0f..03d6204 100644
--- a/kexec/arch/arm64/crashdump-arm64.c
+++ b/kexec/arch/arm64/crashdump-arm64.c
@@ -90,8 +90,16 @@ static int iomem_range_callback(void *UNUSED(data), int UNUSED(nr),
 	else if (strncmp(str, SYSTEM_RAM, strlen(SYSTEM_RAM)) == 0)
 		return mem_regions_alloc_and_add(&system_memory_rgns,
 						base, length, RANGE_RAM);
-	else if (strncmp(str, KERNEL_CODE, strlen(KERNEL_CODE)) == 0)
-		elf_info.kern_paddr_start = base;
+	else if (strncmp(str, KERNEL_CODE, strlen(KERNEL_CODE)) == 0) {
+		/*
+		 * old: kernel_code.start   = __pa_symbol(_text);
+		 * new: kernel_code.start   = __pa_symbol(_stext);
+		 *
+		 * By utilizing the fact that paddr(_text) should align on 2MB, plus
+		 * _stext - _text <= 64K.
+		 */
+		elf_info.kern_paddr_start = base & ((0xffffffffffffffffUL) << 21);
+	}
 	else if (strncmp(str, KERNEL_DATA, strlen(KERNEL_DATA)) == 0)
 		elf_info.kern_size = base + length - elf_info.kern_paddr_start;
 
-- 
2.29.2


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Re: [PATCHv2] arm64/crashdump-arm64: deduce the paddr of _text

[Simon Horman]

On Wed, May 26, 2021 at 06:41:28PM +0800, Pingfan Liu wrote:
> Since kernel commit e2a073dde921 ("arm64: omit [_text, _stext) from
> permanent kernel mapping"), the physical address of 'Kernel code' in
> /proc/iomem is mapped from _text, instead, from _stext.
> 
> Taking the compatibility into account, it had better deduce the paddr of
> _text despite of the unavailability through /proc/iomem. It can be
> achieved by utilizing the fact _text aligned on 2MB.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> Cc: Simon Horman <horms@verge.net.au>
> To: kexec@lists.infradead.org
> ---
> v1 -> v2:
>  deduce paddr of _text to cope with compability.

Thanks, and sorry for the delay.

Applied.

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