On Tue, Aug 23, 2016 at 01:34:21PM +0530, Pratyush Anand wrote:
> On 23/08/2016:02:29:03 PM, AKASHI Takahiro wrote:
> > Pratyush,
> >
> > 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.
> >
> > Who specifies the kernel load address, 0x8002080000 and why?
>
> May be I could not get the question. This load address is coming from the 1st
> kernel.
My question is why we need to use this value, 0x8002080000,
as the kernel load address.
I guess that, on Seattle platform, 0x8000000000-0x8001e80000 is
used for a specific purpose and the kernel must be loaded above
0x8001e80000.
Since PHYS_OFFSET must be 2MB aligned, the lowest kernel load address
should be:
0x8002000000 + 0x80000(default TEXT_OFFSET).
> >
> > Since image_arm64_load() also use
> > get_phys_offset() + arm64_mem.text_offset (== 0x8000080000)
> > as the load address unconditionally, doesn't kexec fail on Seattle?
>
> Yes, had n't tried kexec with binary image. It fails.
> I think image_base should be virt_to_phys(get_kernel_sym("_text")) for
> !KEXEC_ON_CRASH.
So all what we expect from kexec-tools as a sort of boot loader,
we should be able to specify the command line like:
$ kexec --load vmlinux (or Image) --mem-min=0x8001e80000 ...
(We could use get_kernel_sym("_text"), but don't have to.)
I'm going to modify our arm64 port in this way.
Thanks,
-Takahiro AKASHI
> ~Pratyush
>
> >
> > -Takahiro AKASHI
> >
> > > (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]
> > > 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.
> > >
> > > (4) Further more, vmcore must have first PT_LOAD segment as kernel text area.
> > > 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
