[PATCH v2 4/5] LoongArch/kexec_file: Add crash dump support

[Youling Tang]

From: Youling Tang <tangyouling at kylinos.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 at start" to cmdline.
- Add the "mem=size at start" 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 at kylinos.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 at start" 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 at 0x%lx ",
+		elfcorehdr_sz, image->elf_load_addr);
+	*cmdline_tmplen += elfcorehdr_strlen;
+}
+
+/*
+ * Adds the "mem=size at start" 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 at 0x%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 at 0x%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 at start parameter to the command line */
+		cmdline_add_elfcorehdr(image, &cmdline_tmplen, modified_cmdline, headers_sz);
+
+		/* Add the mem=size at start parameter to the command line */
+		cmdline_add_mem(image, &cmdline_tmplen, modified_cmdline);
+	}
+#endif
+
 	/* load initrd */
 	if (initrd) {
 		kbuf.buffer = initrd;
-- 
2.43.0