[PATCH 5/6] LoongArch/kexec_file: Add "mem" parameter to limit memory usage of kdump kernel

[Youling Tang]

From: Youling Tang <tangyouling at kylinos.cn>

Add the "mem=size at start" parameter to the cmdline and pass it to the
capture kernel. Limit the runtime memory area for capturing the kernel
to avoid disrupting the production kernel site.

Signed-off-by: Youling Tang <tangyouling at kylinos.cn>
---
 arch/loongarch/kernel/machine_kexec_file.c | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 06def654cc09..7da88c80cace 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -89,6 +89,26 @@ static void cmdline_add_elfcorehdr(struct kimage *image, unsigned long *cmdline_
 	*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. */
@@ -136,6 +156,7 @@ int load_other_segments(struct kimage *image,
 	/* 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) {
@@ -165,6 +186,9 @@ int load_other_segments(struct kimage *image,
 
 		/* 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
 
-- 
2.34.1