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Sun, 22 Jul 2018 22:37:58 -0700 (PDT) Date: Mon, 23 Jul 2018 14:39:25 +0900 From: AKASHI Takahiro To: James Morse Cc: catalin.marinas@arm.com, will.deacon@arm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de, ard.biesheuvel@linaro.org, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 11/15] arm64: kexec_file: add crash dump support Message-ID: <20180723053923.GN11258@linaro.org> Mail-Followup-To: AKASHI Takahiro , James Morse , catalin.marinas@arm.com, will.deacon@arm.com, dhowells@redhat.com, vgoyal@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de, ard.biesheuvel@linaro.org, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20180711074203.3019-1-takahiro.akashi@linaro.org> <20180711074203.3019-12-takahiro.akashi@linaro.org> <9efd0567-35dc-7435-74d6-1b540f3e5b9f@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9efd0567-35dc-7435-74d6-1b540f3e5b9f@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On Wed, Jul 18, 2018 at 05:50:22PM +0100, James Morse wrote: > 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? Do you mean elf_load_addr? You're right. But kexec_buf defined mem as unsigned long and so I'd rather change dtb_mem to unsigned long instead of elf_load_addr, which will also be renamed to elf_headers_mem for clarification. > (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. OK. > 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); OK. > > + 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? Ah, yes. > > + 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; No worries. kexec_add_buffer() will limit the search only within crashk_res anyway. On the other hand, the code: > > + if (image->type == KEXEC_TYPE_CRASH) { (snip) > > + kbuf.buf_min = crashk_res.start; > > + kbuf.buf_max = crashk_res.end + 1; can be misleading. I will fix it as follows: | kbuf.buf_min = kernel_load_addr + kernel_size; | kbuf.buf_max = ULONG_MAX; (and likewise, will fix image_load().) Thank you again for your valuable comments. Are you reviewing other patches in my v11? If not, I will post v12 tomorrow. -Takahiro AKASHI > > 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