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Message-Id: <20250820055700.24344-5-youling.tang@linux.dev>
Date: Wed, 20 Aug 2025 13:56:59 +0800
From: Youling Tang <youling.tang@...ux.dev>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
Baoquan He <bhe@...hat.com>,
Yao Zi <ziyao@...root.org>,
kexec@...ts.infradead.org,
loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org,
youling.tang@...ux.dev,
Youling Tang <tangyouling@...inos.cn>
Subject: [PATCH v2 4/5] LoongArch/kexec_file: Add crash dump support
From: Youling Tang <tangyouling@...inos.cn>
Enabling crash dump (kdump) includes:
- Prepare contents of ELF header of a core dump file, /proc/vmcore,
using crash_prepare_elf64_headers().
- Add "elfcorehdr=size@...rt" to cmdline.
- Add the "mem=size@...rt" parameter to the command line and pass it to
the capture kernel. Limit the runtime memory area of the captured
kernel to avoid disrupting the production kernel's runtime state.
Signed-off-by: Youling Tang <tangyouling@...inos.cn>
---
arch/loongarch/kernel/machine_kexec_file.c | 117 +++++++++++++++++++++
1 file changed, 117 insertions(+)
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index dc6e37457559..1d47be06549e 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -35,6 +35,83 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
return kexec_image_post_load_cleanup_default(image);
}
+#ifdef CONFIG_CRASH_DUMP
+
+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 = 2; /* for exclusion of crashkernel region */
+ for_each_mem_range(i, &start, &end)
+ nr_ranges++;
+
+ cmem = kmalloc(struct_size(cmem, ranges, nr_ranges), GFP_KERNEL);
+ if (!cmem)
+ return -ENOMEM;
+
+ cmem->max_nr_ranges = nr_ranges;
+ cmem->nr_ranges = 0;
+ for_each_mem_range(i, &start, &end) {
+ 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;
+
+ if (crashk_low_res.end) {
+ ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+ if (ret)
+ goto out;
+ }
+
+ ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+
+out:
+ kfree(cmem);
+ return ret;
+}
+
+/* Adds the "elfcorehdr=size@...rt" command line parameter to command line. */
+static void cmdline_add_elfcorehdr(struct kimage *image, unsigned long *cmdline_tmplen,
+ char *modified_cmdline, unsigned long elfcorehdr_sz)
+{
+ int elfcorehdr_strlen = 0;
+
+ elfcorehdr_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "elfcorehdr=0x%lx@...lx ",
+ elfcorehdr_sz, image->elf_load_addr);
+ *cmdline_tmplen += elfcorehdr_strlen;
+}
+
+/*
+ * Adds the "mem=size@...rt" command line parameter to command line, indicating the
+ * memory region the new kernel can use to boot into.
+ */
+static void cmdline_add_mem(struct kimage *image, unsigned long *cmdline_tmplen,
+ char *modified_cmdline)
+{
+ int mem_strlen = 0;
+
+ mem_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "mem=0x%llx@...llx ",
+ crashk_res.end - crashk_res.start + 1, crashk_res.start);
+ *cmdline_tmplen += mem_strlen;
+
+ if (crashk_low_res.end) {
+ mem_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "mem=0x%llx@...llx ",
+ crashk_low_res.end - crashk_low_res.start + 1, crashk_low_res.start);
+ *cmdline_tmplen += mem_strlen;
+ }
+}
+
+#endif
+
/* Adds the "initrd=start,size" command line parameter to command line. */
static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmplen,
char *modified_cmdline, unsigned long initrd)
@@ -76,6 +153,46 @@ int load_other_segments(struct kimage *image,
/* Ensure it's nul terminated */
modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
+#ifdef CONFIG_CRASH_DUMP
+ /* load elf core header */
+ void *headers;
+ unsigned long headers_sz;
+
+ if (image->type == KEXEC_TYPE_CRASH) {
+ ret = prepare_elf_headers(&headers, &headers_sz);
+ if (ret) {
+ pr_err("Preparing elf core header failed\n");
+ goto out_err;
+ }
+
+ kbuf.buffer = headers;
+ kbuf.bufsz = headers_sz;
+ kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+ kbuf.memsz = headers_sz;
+ kbuf.buf_align = SZ_64K; /* largest supported page size */
+ kbuf.buf_max = ULONG_MAX;
+ kbuf.top_down = true;
+
+ ret = kexec_add_buffer(&kbuf);
+ if (ret) {
+ vfree(headers);
+ goto out_err;
+ }
+ image->elf_headers = headers;
+ image->elf_load_addr = kbuf.mem;
+ image->elf_headers_sz = headers_sz;
+
+ kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+ image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
+
+ /* Add the elfcorehdr=size@...rt parameter to the command line */
+ cmdline_add_elfcorehdr(image, &cmdline_tmplen, modified_cmdline, headers_sz);
+
+ /* Add the mem=size@...rt parameter to the command line */
+ cmdline_add_mem(image, &cmdline_tmplen, modified_cmdline);
+ }
+#endif
+
/* load initrd */
if (initrd) {
kbuf.buffer = initrd;
--
2.43.0
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