[PATCH v2 0/7] (kexec-tools) arm64: add kdump support
AKASHI Takahiro
takahiro.akashi at linaro.org
Fri Aug 19 00:19:31 PDT 2016
Pratyush, Geoff
# If I had Seattle, I could debug easily :)
On Wed, Aug 10, 2016 at 11:26:48PM +0530, Pratyush Anand wrote:
> Hi Geoff and Takahiro,
>
> I am having some issues with kexec+kdump while working with Seattle platform. On
> top level, kernel crashes in copy_oldmem_page(), because it gets wrong offset
> for log_buf during vmcore-dmesg save.
>
> Here is the detail:
>
> (1) From /proc/iomem, these are the "System RAM" Components:
>
> 8000000000-8001e7ffff : System RAM
> 8001e80000-83ff17ffff : System RAM
> 8002080000-8002b3ffff : Kernel code
> 8002c40000-800348ffff : Kernel data
> 807fe00000-80ffdfffff : Crash kernel
> 83ff180000-83ff1cffff : System RAM
> 83ff1d0000-83ff21ffff : System RAM
> 83ff220000-83ffe4ffff : System RAM
> 83ffe50000-83ffffffff : System RAM
>
> (2) From kexec-tools debug print I see following:
> elf_arm64_load: e_entry: fffffc0008080000 -> 0000008000080000
> elf_arm64_load: p_vaddr: fffffc0008080000 -> 0000008000080000
> elf_arm64_load: header_offset: 0000000000000000
> elf_arm64_load: text_offset: 0000000000080000
> elf_arm64_load: image_size: 0000000001410000
> elf_arm64_load: phys_offset: 0000008000000000
> elf_arm64_load: page_offset: fffffc0008000000
>
> I understand that "Kernel Code start physical address" 0x8002080000 should map
> to e_entry vaddr which is 0xfffffc0008080000. However, kexec-tools debug print
> shows that e_entry vaddr maps to PA 8000080000 which seems wrong.
Obviously, virt_to_phys() is wrong.
As you know, we have to calculate virt_to_phys() in a different way
depending on whether the vaddr is greater than PAGE_OFFSET (linear mapping)
or not (kernel image mapping).
See the kernel's include/asm/memory.h.
Geoff, please update this function.
> (3) further page_offset (or vp_offset in your new code) is calculated
> as:arm64_mem.page_offset = ehdr.e_entry - arm64_mem.text_offset;
>
> Current calcualtion of page_offset leads to wrong configuration of VA of alls
> PT_LOAD (see below). Ultimately, this is also leading to kernel crash during
> vmcore-dmesg and vmcore save operations, because we pass an offset to pread()
> system call which maps to wrong physical address.
>
> Elf header: p_type = 1, p_offset = 0x8000000000 p_paddr = 0x8000000000
> p_vaddr = 0xfffffc0008000000 p_filesz = 0x1e80000 p_memsz = 0x1e80000
> [0xfffffc0008000000 should be mapping to 0x8002000000 and not 0x8000000000]
I think that your comment here is wrong.
This program header indicates the first memory region in the 1st kernel,
that is,
8000000000-8001e7ffff : System RAM
Is this region really part of "System RAM?"
Can you show me the "Virtual kernel memory layout" in dmesg?
> Elf header: p_type = 1, p_offset = 0x8001e80000 p_paddr = 0x8001e80000
> p_vaddr = 0xfffffc0009e80000 p_filesz = 0x7df80000 p_memsz = 0x7df80000
> Elf header: p_type = 1, p_offset = 0x80ffe00000 p_paddr = 0x80ffe00000
> p_vaddr = 0xfffffc0107e00000 p_filesz = 0x2ff380000 p_memsz = 0x2ff380000
> Elf header: p_type = 1, p_offset = 0x83ff180000 p_paddr = 0x83ff180000
> p_vaddr = 0xfffffc0407180000 p_filesz = 0x50000 p_memsz = 0x50000
> Elf header: p_type = 1, p_offset = 0x83ff1d0000 p_paddr = 0x83ff1d0000
> p_vaddr = 0xfffffc04071d0000 p_filesz = 0x50000 p_memsz = 0x50000
> Elf header: p_type = 1, p_offset = 0x83ff220000 p_paddr = 0x83ff220000
> p_vaddr = 0xfffffc0407220000 p_filesz = 0xc30000 p_memsz = 0xc30000
> Elf header: p_type = 1, p_offset = 0x83ffe50000 p_paddr = 0x83ffe50000
> p_vaddr = 0xfffffc0407e50000 p_filesz = 0x1b0000 p_memsz = 0x1b0000
>
> May be following should be better.
> arm64_mem.page_offset = ehdr.e_entry - "kernel Code Start PA" + phys_offset.
Probably not.
> (4) Further more, vmcore must have first PT_LOAD segment as kernel text area.
Which part of the code do you think depends on this assumption?
Thanks,
-Takahiro AKASHI
> In this platform we have first "System RAM" area as 8000000000-8001e7ffff which
> is not matching to "Kernel code" area. Therefore, we should provide support of
> "kern_size" so that first PT_LOAD is kernel text area.
>
> ~Pratyush
> On 09/08/2016:11:00:25 AM, AKASHI Takahiro wrote:
> > My kernel patches of kdump suport on arm64 are currently under reviews [1].
> >
> > This patchset is synced with them (v24) and provides necessary changes for
> > kexec-tools. It should be applied on top of Geoff's kexec-tools patches
> > v3[2] along with a bugfix[3].
> >
> > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/447597.html
> > [2] http://lists.infradead.org/pipermail/kexec/2016-August/016768.html
> > [3] http://lists.infradead.org/pipermail/kexec/2016-July/016664.html
> >
> > Changes for v2:
> > - Trim a temoprary buffer in setup_2nd_dtb()
> > - Add patch#6("kexec: generalize and rename get_kernel_stext_sym()")
> > - Update patch#7 from Pratyush
> > (re-worked by akashi)
> >
> > AKASHI Takahiro (5):
> > arm64: kdump: identify memory regions
> > arm64: kdump: add elf core header segment
> > arm64: kdump: set up kernel image segment
> > arm64: kdump: set up other segments
> > arm64: kdump: add DT properties to crash dump kernel's dtb
> >
> > Pratyush Anand (2):
> > kexec: generalize and rename get_kernel_stext_sym()
> > arm64: kdump: Add support for binary image files
> >
> > kexec/arch/arm/crashdump-arm.c | 40 +------
> > kexec/arch/arm64/Makefile | 2 +
> > kexec/arch/arm64/crashdump-arm64.c | 188 +++++++++++++++++++++++++++++++-
> > kexec/arch/arm64/crashdump-arm64.h | 18 ++-
> > kexec/arch/arm64/include/arch/options.h | 8 +-
> > kexec/arch/arm64/kexec-arm64.c | 91 ++++++++++++++--
> > kexec/arch/arm64/kexec-elf-arm64.c | 23 +++-
> > kexec/arch/arm64/kexec-image-arm64.c | 60 +++++++++-
> > kexec/arch/i386/crashdump-x86.c | 32 +-----
> > kexec/crashdump.c | 37 +++++++
> > kexec/crashdump.h | 1 +
> > 11 files changed, 407 insertions(+), 93 deletions(-)
> >
> > --
> > 2.9.0
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