Messages in this thread | | | Subject | Re: [PATCH v11 11/15] arm64: kexec_file: add crash dump support | From | James Morse <> | Date | Wed, 18 Jul 2018 17:50:22 +0100 |
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Hi Akashi,
On 11/07/18 08:41, AKASHI Takahiro wrote: > Enabling crash dump (kdump) includes > * prepare contents of ELF header of a core dump file, /proc/vmcore, > using crash_prepare_elf64_headers(), and > * add two device tree properties, "linux,usable-memory-range" and > "linux,elfcorehdr", which represent respectively a memory range > to be used by crash dump kernel and the header's location
> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h > index 69333694e3e2..eeb5766928b0 100644 > --- a/arch/arm64/include/asm/kexec.h > +++ b/arch/arm64/include/asm/kexec.h > @@ -99,6 +99,10 @@ static inline void crash_post_resume(void) {} > struct kimage_arch { > phys_addr_t dtb_mem; > void *dtb_buf; > + /* Core ELF header buffer */
> + void *elf_headers;
Shouldn't this be a phys_addr_t if it comes from kbuf.mem? (dtb_mem is, and they type tells us which way round the runtime/kexec-time pointers are)
> + unsigned long elf_headers_sz; > + unsigned long elf_load_addr; > }; > > /**
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > index a0b44fe18b95..261564df7210 100644 > --- a/arch/arm64/kernel/machine_kexec_file.c > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -132,6 +173,45 @@ static int setup_dtb(struct kimage *image, > return ret; > } > > +static int prepare_elf_headers(void **addr, unsigned long *sz) > +{ > + struct crash_mem *cmem; > + unsigned int nr_ranges; > + int ret; > + u64 i; > + phys_addr_t start, end;
> + nr_ranges = 1; /* for exclusion of crashkernel region */ > + for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE, 0, > + &start, &end, NULL)
Nit: flags = MEMBLOCK_NONE? Just to make it obvious this is how MEMBLOCK_NOMAP regions are weeded out.
This is going to get interesting if we ever support hotpluggable memory... but it works for now and implicitly removes the nomap regions.
> + nr_ranges++;
> + > + cmem = kmalloc(sizeof(struct crash_mem) + > + sizeof(struct crash_mem_range) * nr_ranges, GFP_KERNEL); > + if (!cmem) > + return -ENOMEM; > + > + cmem->max_nr_ranges = nr_ranges; > + cmem->nr_ranges = 0; > + for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE, 0, > + &start, &end, NULL) { > + cmem->ranges[cmem->nr_ranges].start = start; > + cmem->ranges[cmem->nr_ranges].end = end - 1; > + cmem->nr_ranges++; > + } > + > + /* Exclude crashkernel region */ > + ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
> + if (ret) > + goto out; > + > + ret = crash_prepare_elf64_headers(cmem, true, addr, sz); > + > +out:
Nit: You could save the goto if you wrote this as: | if (!ret) | ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> + kfree(cmem); > + return ret; > +} > + > int load_other_segments(struct kimage *image, > unsigned long kernel_load_addr, > unsigned long kernel_size, > @@ -139,11 +219,43 @@ int load_other_segments(struct kimage *image, > char *cmdline, unsigned long cmdline_len) > { > struct kexec_buf kbuf; > + void *hdrs_addr; > + unsigned long hdrs_sz; > unsigned long initrd_load_addr = 0; > char *dtb = NULL; > unsigned long dtb_len = 0; > int ret = 0; > > + /* load elf core header */ > + if (image->type == KEXEC_TYPE_CRASH) { > + ret = prepare_elf_headers(&hdrs_addr, &hdrs_sz); > + if (ret) { > + pr_err("Preparing elf core header failed\n"); > + goto out_err; > + } > + > + kbuf.image = image; > + kbuf.buffer = hdrs_addr; > + kbuf.bufsz = hdrs_sz; > + kbuf.memsz = hdrs_sz;
> + kbuf.buf_align = PAGE_SIZE;
Whose PAGE_SIZE?
Won't this break if the kdump kernel is 64K pages, but the first kernel uses 4K? Should we change this to the largest supported PAGE_SIZE: SZ_64K?
> + kbuf.buf_min = crashk_res.start; > + kbuf.buf_max = crashk_res.end + 1; > + kbuf.top_down = true; > + > + ret = kexec_add_buffer(&kbuf); > + if (ret) { > + vfree(hdrs_addr); > + goto out_err; > + } > + image->arch.elf_headers = hdrs_addr; > + image->arch.elf_headers_sz = hdrs_sz; > + image->arch.elf_load_addr = kbuf.mem; > + > + pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n", > + image->arch.elf_load_addr, hdrs_sz, hdrs_sz); > + } > + > kbuf.image = image; > /* not allocate anything below the kernel */ > kbuf.buf_min = kernel_load_addr + kernel_size;
I think the initramfs can escape the crash kernel range because you add to the buf_max region: | /* within 1GB-aligned window of up to 32GB in size */ | kbuf.buf_max = round_down(kernel_load_addr, SZ_1G) | + (unsigned long)SZ_1G * 32;
I think we need a helper to clamp these min/max ranges to within the crash kernel range, as its needs doing in a few places.
Thanks,
James
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