On Sun, Aug 20, 2023 at 3:16 AM Alexander Kamensky <alexander.kamensky42@xxxxxxxxx> wrote: > > In the latest openembedded with aarch64 image that uses 6.4.3 kernel on qemu I > tried to run makedumpfile in secondary kernel with /proc/vmcore. It failed as > follows: > > > root@qemuarm64:~# makedumpfile -c -F /proc/vmcore > /dev/null > > read_from_vmcore: Can't seek the dump memory(/proc/vmcore). (offset: ffffffc0123fa000) Invalid argument > > readpage_elf: Can't read the dump memory(/proc/vmcore). > > <snip> > > It turns out that not all parts for /proc/vmcore are readable: > > > root@qemuarm64:~# cat /proc/vmcore > /dev/null > > [ 136.394931] Internal error: synchronous external abort: 0000000096000010 [#1] PREEMPT SMP > > [ 136.422434] Modules linked in: > > <snip> > > Binary search of different kernel versions I found that the issue goes back to > 5.11. It works fine with 5.10 version of the kernel. > > After running secondary kernel under qemu gdb, I've found that the primary kernel > main memory segment in elfcorehdr has wrong address and size. > > Looking at kexec output with debug enabled at the time when it loads secondary > crash kernel I saw the following: > > > Kernel text Elf header: p_type = 1, p_offset = 0x4030200000 p_paddr = 0x4030200000 p_vaddr = 0xffffffffffffffff p_filesz = 0xffffffc011410000 p_memsz = 0xffffffc011410000 > > These values come from elf_info variable and are set in iomem_range_callback > function. The function gets the following input on my system: > > root@qemuarm64:~# cat /proc/iomem | grep "Kernel code" > 40210000-40feffff : Kernel code > root@qemuarm64:~# cat /proc/kallsyms | grep -e ' _text$' This is the crux of the problem. Could you say something about how it disappeared? On my side, I can see this info on 6.2.14-300.fc38.aarch64 grep -w _text /proc/kallsyms ffffc705d8500000 T _text Thanks, Pingfan > root@qemuarm64:~# cat /proc/kallsyms | grep -e ' _stext$' > ffffffc010010000 T _stext > root@qemuarm64:~# cat /proc/kallsyms | grep -e ' __init_begin$' > ffffffc010df0000 T __init_begin > > the function calculates elf_info.kern_paddr_start address similar to > these manual steps: > > base = 0x40210000 > length = 0x40feffff - 0x40210000 + 0x1 = 0xde0000 > kva_text_end - kva_stext = 0xffffffc010df0000 - 0xffffffc010010000 = 0xde0000 > > elf_info.kern_paddr_start = base - (kva_stext - kva_text) = > 0x40210000 - 0xffffffc010010000 = 0x4030200000 > > since 'length' and 'kva_text_end - kva_stext' are equal the function calculate > elf_info.kern_paddr_start as in legacy case: > > if (kva_text_end - kva_stext == length) > elf_info.kern_paddr_start = base - (kva_stext - kva_text); // <--------- > else > elf_info.kern_paddr_start = base; > > but my kernel is not legacy and kva_text is zero. > > The fix is just to add a check for kva_text not being zero before following the > legacy case. > > Signed-off-by: Alexander Kamensky <alexander.kamensky42@xxxxxxxxx> > --- > kexec/arch/arm64/crashdump-arm64.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c > index 3098315..639c82a 100644 > --- a/kexec/arch/arm64/crashdump-arm64.c > +++ b/kexec/arch/arm64/crashdump-arm64.c > @@ -82,7 +82,7 @@ static int iomem_range_callback(void *UNUSED(data), int UNUSED(nr), > * For compatibility, deduce by comparing the gap "__init_begin - _stext" > * and the res size of "Kernel code" in /proc/iomem > */ > - if (kva_text_end - kva_stext == length) > + if ((kva_text_end - kva_stext == length) && (kva_text != 0)) > elf_info.kern_paddr_start = base - (kva_stext - kva_text); > else > elf_info.kern_paddr_start = base; > -- > 2.41.0 > > > _______________________________________________ > kexec mailing list > kexec@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/kexec > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
