Re: [Crash-utility] [crash-utility][ARM64][patch] Auto calculate kimage_voffset by kaslr offset

----- Original Message ----- Hello Yueyi, I have a few questions about this patch. First, can you clarify the kernel version and the dumpfile type that you are trying to address? I understand the confusion, given that arm64 kdump/KASLR support is still being debated upstream. Eventually, arm64 kdump-generated dumpfiles will have "NUMBER(kimage_voffset)" and "NUMBER(PHYS_OFFSET)" VMCOREINFO entries, which will simplify things significantly (and you can see that the crash utility already has support for them in advance). It seems that this patch would only be applicable when looking at an ELF dumpfile, given that your arch_calc_kimage_voffset() function calls arm_kdump_phys_base() -- which only applies if you are looking at an ELF dumpfile: +static void +arm64_calc_kimage_voffset(void) +{ + struct machine_specific *ms = machdep->machspec; + ulong kimage_offset; + ulong phys_offset; + struct syment *sp; + + if (machdep->flags & KIMG_VOFFSET) /* --machdep override */ + return; + + if ((kt->flags2 & KASLR) && (kt->flags & RELOC_SET)){ + arm_kdump_phys_base(&phys_offset); + ms->kimage_voffset = ms->vmalloc_start_addr + (kt->relocate * -1) - phys_offset; + } + +} Is that correct? And if so, why not call arm64_kdump_phys_base() instead? Because I see in your "error message without the patch" above, the phys_base seems to have been calculated correctly to be 40000000, so it looks like the call from arm64_calc_phys_offset() to arm64_kdump_phys_base() must have worked. (since arm64_kdump_phys_base() ultimately calls arm_kdump_phys_base() if nothing else works) So what would happen if you called arm64_calc_phys_offset() *before* your new function? Wouldn't it correctly determine phys_offset? And then there would be no need for you to call it in your new function: @@ -324,6 +325,9 @@ arm64_init(int when) machdep->init_kernel_pgd = arm64_init_kernel_pgd; /* use machdep parameters */ + arm64_calc_kimage_voffset(); + + /* use machdep parameters */ arm64_calc_phys_offset(); In addition, arm64_calc_phys_offset() also tries to determine the phys_offset value for compressed kdump dumpfiles and live systems. If the dumpfile has been compressed (by the makedumpfile facility), or if you are running on a live system, then your patch would fail to determine phys_offset. But if you were to call arm64_calc_phys_offset() instead, it would call diskdump_phys_base() for compressed dumpfiles, or try to determine the phys_offset value from /proc/iomem on live systems. Dave