[PATCH v4 0/7] Add kexec_file support for LoongArch

[PATCH v4 0/7] Add kexec_file support for LoongArch

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

This patchset implement kexec_file_load() support on LoongArch.

This patch series enables us to load the LoongArch vmlinuz.efi(pez) or
vmlinux.efi(pei) or vmlinux(elf) by specifying its file decriptor,
instead of user-filled buffer via kexec_load() syscall.

To use kexec_file_load() system call, instead of kexec_load(), at kexec
command, '-s' options must be specified. kexec-tools needs to apply the
corresponding patches. These patches can be found in repository [1] and
will be submitted to the kexec-tools community later.

The basic usage of kexec_file is:
1) Load second kernel image:
 # kexec -s -l vmlinuz.efi --initrd=initrd.img --reuse-cmdline

2) Startup second kernel:
 # kexec -e

For kdump:
1) Load capture kernel image:
 # kexec -s -p vmlinuz.efi --initrd=initrd.img --reuse-cmdline

2) Do something to crash, like:
 # echo c > /proc/sysrq-trigger

Link:
[1] https://github.com/tangyouling/kexec-tools/commits/main/

Changelog:
 v4:
 * Add the character "kexec_file" to the command-line parameter.
 * Fixed the issue where kexec_file failed to load the KASLR kernel
   startup.
 * Modify the member name of the loongarch_image_header structure.
 * Modify the patch commit message.

 v3:
 * The ELF format kernel loading should not use loongarch_image_header.
 * Separate patch2 into an infrastructure patch and an EFI support
   patch.
 * Adding that kexec_file cannot load non-relocation kernel comments.
 * Some minor modifications.

 v2:
 * Merge some patches.
 * Add support for ELF format images.
 * Rename kexec_image.c to kexec_efi.c .
 * When KEXEC_FILE is enabled, RELOCATABLE is selected by default.
 * Some minor modifications.

Youling Tang (7):
  LoongArch: Add struct loongarch_image_header for kernel image
  LoongArch: Add preparatory infrastructure for kexec_file
  LoongArch/kexec_file: Support loading EFI binary file
  LoongArch/kexec_file: Support loading ELF binary file
  LoongArch/kexec_file: Add crash dump support
  LoongArch: Automatically disable kaslr when the kernel loads from
    kexec_file
  LoongArch: Enable CONFIG_KEXEC_FILE

 arch/loongarch/Kconfig                     |  10 +
 arch/loongarch/configs/loongson3_defconfig |   1 +
 arch/loongarch/include/asm/image.h         |  53 +++++
 arch/loongarch/include/asm/kexec.h         |  13 ++
 arch/loongarch/kernel/Makefile             |   1 +
 arch/loongarch/kernel/kexec_efi.c          | 114 ++++++++++
 arch/loongarch/kernel/kexec_elf.c          | 105 +++++++++
 arch/loongarch/kernel/machine_kexec.c      |  37 ++--
 arch/loongarch/kernel/machine_kexec_file.c | 244 +++++++++++++++++++++
 arch/loongarch/kernel/relocate.c           |   4 +
 10 files changed, 569 insertions(+), 13 deletions(-)
 create mode 100644 arch/loongarch/include/asm/image.h
 create mode 100644 arch/loongarch/kernel/kexec_efi.c
 create mode 100644 arch/loongarch/kernel/kexec_elf.c
 create mode 100644 arch/loongarch/kernel/machine_kexec_file.c

-- 
2.43.0

[PATCH v4 1/7] LoongArch: Add struct loongarch_image_header for kernel image

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

Define a dedicated image header structure for LoongArch architecture to
standardize kernel loading in bootloaders (primarily for kexec_file).

This header includes critical metadata such as PE signature, entry points,
image size and load address offset, etc.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/include/asm/image.h | 36 ++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 arch/loongarch/include/asm/image.h

diff --git a/arch/loongarch/include/asm/image.h b/arch/loongarch/include/asm/image.h
new file mode 100644
index 000000000000..ff539711c9ea
--- /dev/null
+++ b/arch/loongarch/include/asm/image.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * LoongArch binary image header for EFI(PE/COFF) format.
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ */
+
+#ifndef __ASM_IMAGE_H
+#define __ASM_IMAGE_H
+#ifndef __ASSEMBLER__
+
+/**
+ * struct loongarch_image_header
+ *
+ * @dos_sig: Optional PE format 'MZ' signature.
+ * @padding_1: Reserved.
+ * @kernel_entry: Kernel image entry pointer.
+ * @kernel_asize: An estimated size of the memory image size in LSB byte order.
+ * @text_offset: The image load offset in LSB byte order.
+ * @padding_2: Reserved.
+ * @pe_header: Optional offset to a PE format header.
+ **/
+
+struct loongarch_image_header {
+	uint8_t dos_sig[2];
+	uint16_t padding_1[3];
+	uint64_t kernel_entry;
+	uint64_t kernel_asize;
+	uint64_t text_offset;
+	uint32_t padding_2[7];
+	uint32_t pe_header;
+};
+
+#endif /* __ASSEMBLER__ */
+#endif /* __ASM_IMAGE_H */
-- 
2.43.0

[PATCH v4 2/7] LoongArch: Add preparatory infrastructure for kexec_file

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

Add some preparatory infrastructure:
- Add support for loading other segments.
- Add command line processing.
- Other minor modifications.

This initrd will be passed to the second kernel via the command line
'initrd=start,size'.

The 'kexec_file' command line parameter indicates that the kernel is
loaded via kexec_file.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/Kconfig                     |   9 ++
 arch/loongarch/include/asm/kexec.h         |  11 ++
 arch/loongarch/kernel/Makefile             |   1 +
 arch/loongarch/kernel/machine_kexec.c      |  37 +++---
 arch/loongarch/kernel/machine_kexec_file.c | 126 +++++++++++++++++++++
 5 files changed, 171 insertions(+), 13 deletions(-)
 create mode 100644 arch/loongarch/kernel/machine_kexec_file.c

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index f0abc38c40ac..490dc6eed749 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -625,6 +625,15 @@ config CPU_HAS_PREFETCH
 config ARCH_SUPPORTS_KEXEC
 	def_bool y
 
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool 64BIT
+
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
+	depends on KEXEC_FILE
+	select HAVE_IMA_KEXEC if IMA
+	select RELOCATABLE
+
 config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
 
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index cf95cd3eb2de..ed7e3fc8571e 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -41,6 +41,17 @@ struct kimage_arch {
 	unsigned long systable_ptr;
 };
 
+#ifdef CONFIG_KEXEC_FILE
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image);
+#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
+
+extern int load_other_segments(struct kimage *image,
+		unsigned long kernel_load_addr, unsigned long kernel_size,
+		char *initrd, unsigned long initrd_len,
+		char *cmdline, unsigned long cmdline_len);
+#endif
+
 typedef void (*do_kexec_t)(unsigned long efi_boot,
 			   unsigned long cmdline_ptr,
 			   unsigned long systable_ptr,
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 6f5a4574a911..67b9b214d212 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -62,6 +62,7 @@ obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_RELOCATABLE)	+= relocate.o
 
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_UNWINDER_GUESS)	+= unwind_guess.o
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
index f9381800e291..d5accdc4576d 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -70,18 +70,28 @@ int machine_kexec_prepare(struct kimage *kimage)
 	kimage->arch.efi_boot = fw_arg0;
 	kimage->arch.systable_ptr = fw_arg2;
 
-	/* Find the command line */
-	for (i = 0; i < kimage->nr_segments; i++) {
-		if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, strlen(bootloader))) {
-			if (!copy_from_user(cmdline_ptr, kimage->segment[i].buf, COMMAND_LINE_SIZE))
-				kimage->arch.cmdline_ptr = (unsigned long)cmdline_ptr;
-			break;
+	if (kimage->file_mode == 1) {
+		/*
+		 * kimage->cmdline_buf will be released in kexec_file_load, so copy to
+		 * the KEXEC_CMDLINE_ADDR safe area.
+		 */
+		memcpy((void *)KEXEC_CMDLINE_ADDR, (void *)kimage->arch.cmdline_ptr,
+					strlen((char *)kimage->arch.cmdline_ptr) + 1);
+		kimage->arch.cmdline_ptr = (unsigned long)KEXEC_CMDLINE_ADDR;
+	} else {
+		/* Find the command line */
+		for (i = 0; i < kimage->nr_segments; i++) {
+			if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, strlen(bootloader))) {
+				if (!copy_from_user(cmdline_ptr, kimage->segment[i].buf, COMMAND_LINE_SIZE))
+					kimage->arch.cmdline_ptr = (unsigned long)cmdline_ptr;
+				break;
+			}
 		}
-	}
 
-	if (!kimage->arch.cmdline_ptr) {
-		pr_err("Command line not included in the provided image\n");
-		return -EINVAL;
+		if (!kimage->arch.cmdline_ptr) {
+			pr_err("Command line not included in the provided image\n");
+			return -EINVAL;
+		}
 	}
 
 	/* kexec/kdump need a safe page to save reboot_code_buffer */
@@ -287,9 +297,10 @@ void machine_kexec(struct kimage *image)
 	/* We do not want to be bothered. */
 	local_irq_disable();
 
-	pr_notice("EFI boot flag 0x%lx\n", efi_boot);
-	pr_notice("Command line at 0x%lx\n", cmdline_ptr);
-	pr_notice("System table at 0x%lx\n", systable_ptr);
+	pr_notice("EFI boot flag: 0x%lx\n", efi_boot);
+	pr_notice("Command line addr: 0x%lx\n", cmdline_ptr);
+	pr_notice("Command line string: %s\n", (char *)cmdline_ptr);
+	pr_notice("System table addr: 0x%lx\n", systable_ptr);
 	pr_notice("We will call new kernel at 0x%lx\n", start_addr);
 	pr_notice("Bye ...\n");
 
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
new file mode 100644
index 000000000000..584ce9471e93
--- /dev/null
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kexec_file for LoongArch
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ *
+ * Most code is derived from LoongArch port of kexec-tools
+ */
+
+#define pr_fmt(fmt) "kexec_file: " fmt
+
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/memblock.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <asm/bootinfo.h>
+
+const struct kexec_file_ops * const kexec_file_loaders[] = {
+	NULL
+};
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+	vfree(image->elf_headers);
+	image->elf_headers = NULL;
+	image->elf_headers_sz = 0;
+
+	return kexec_image_post_load_cleanup_default(image);
+}
+
+/* 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)
+{
+	int initrd_strlen;
+
+	initrd_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "initrd=0x%lx,0x%lx ",
+		initrd, image->initrd_buf_len);
+	*cmdline_tmplen += initrd_strlen;
+}
+
+/* Adds the "kexec_file" command line parameter to command line. */
+static void cmdline_add_prefix(unsigned long *cmdline_tmplen, char *modified_cmdline)
+{
+	int prefix_strlen;
+
+	prefix_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "kexec_file ");
+	*cmdline_tmplen += prefix_strlen;
+}
+
+/*
+ * Tries to add the initrd to the image. If it is not possible to find
+ * valid locations, this function will undo changes to the image and return non
+ * zero.
+ */
+int load_other_segments(struct kimage *image,
+			unsigned long kernel_load_addr,
+			unsigned long kernel_size,
+			char *initrd, unsigned long initrd_len,
+			char *cmdline, unsigned long cmdline_len)
+{
+	struct kexec_buf kbuf;
+	unsigned long orig_segments = image->nr_segments;
+	char *modified_cmdline = NULL;
+	unsigned long cmdline_tmplen = 0;
+	unsigned long initrd_load_addr = 0;
+	int ret = 0;
+
+
+	kbuf.image = image;
+	/* not allocate anything below the kernel */
+	kbuf.buf_min = kernel_load_addr + kernel_size;
+
+	modified_cmdline = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
+	if (!modified_cmdline)
+		return -EINVAL;
+
+	cmdline_add_prefix(&cmdline_tmplen, modified_cmdline);
+	/* Ensure it's null terminated */
+	modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
+
+	/* load initrd */
+	if (initrd) {
+		kbuf.buffer = initrd;
+		kbuf.bufsz = initrd_len;
+		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+		kbuf.memsz = initrd_len;
+		kbuf.buf_align = 0;
+		/* 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;
+		kbuf.top_down = false;
+
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			goto out_err;
+		initrd_load_addr = kbuf.mem;
+
+		kexec_dprintk("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+			      initrd_load_addr, kbuf.bufsz, kbuf.memsz);
+
+		/* Add the initrd=start,size parameter to the command line */
+		cmdline_add_initrd(image, &cmdline_tmplen, modified_cmdline, initrd_load_addr);
+	}
+
+	if (cmdline_len + cmdline_tmplen > COMMAND_LINE_SIZE) {
+		pr_err("Appending command line exceeds COMMAND_LINE_SIZE\n");
+		ret = -EINVAL;
+		goto out_err;
+	}
+	memcpy(modified_cmdline + cmdline_tmplen, cmdline, cmdline_len);
+	cmdline = modified_cmdline;
+	image->arch.cmdline_ptr = (unsigned long)cmdline;
+
+	return 0;
+
+out_err:
+	image->nr_segments = orig_segments;
+	kfree(modified_cmdline);
+	return ret;
+}
-- 
2.43.0

[PATCH v4 3/7] LoongArch/kexec_file: Support loading EFI binary file

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

This patch creates kexec_efi_ops to load EFI binary file for
kexec_file_load() syscall.

The efi_kexec_load() as two parts:
- the first part loads the kernel image (vmlinuz.efi or vmlinux.efi)
- the second part loads other segments (eg: initrd, cmdline)

Currently, pez(vmlinuz.efi) and pei(vmlinux.efi) format images are
supported.

The basic usage (vmlinuz.efi or vmlinux.efi):
1) Load second kernel image:
 # kexec -s -l vmlinuz.efi --initrd=initrd.img --reuse-cmdline

2) Startup second kernel:
 # kexec -e

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/include/asm/image.h         |  17 +++
 arch/loongarch/include/asm/kexec.h         |   1 +
 arch/loongarch/kernel/Makefile             |   2 +-
 arch/loongarch/kernel/kexec_efi.c          | 114 +++++++++++++++++++++
 arch/loongarch/kernel/machine_kexec_file.c |   1 +
 5 files changed, 134 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/kernel/kexec_efi.c

diff --git a/arch/loongarch/include/asm/image.h b/arch/loongarch/include/asm/image.h
index ff539711c9ea..982cebd31cac 100644
--- a/arch/loongarch/include/asm/image.h
+++ b/arch/loongarch/include/asm/image.h
@@ -32,5 +32,22 @@ struct loongarch_image_header {
 	uint32_t pe_header;
 };
 
+static const uint8_t loongarch_image_dos_sig[2] = {'M', 'Z'};
+
+/**
+ * loongarch_header_check_dos_sig - Helper to check the loongarch image header.
+ *
+ * Returns non-zero if 'MZ' signature is found.
+ */
+
+static inline int loongarch_header_check_dos_sig(const struct loongarch_image_header *h)
+{
+	if (!h)
+		return 0;
+
+	return (h->dos_sig[0] == loongarch_image_dos_sig[0]
+		&& h->dos_sig[1] == loongarch_image_dos_sig[1]);
+}
+
 #endif /* __ASSEMBLER__ */
 #endif /* __ASM_IMAGE_H */
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index ed7e3fc8571e..34799db933fb 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -42,6 +42,7 @@ struct kimage_arch {
 };
 
 #ifdef CONFIG_KEXEC_FILE
+extern const struct kexec_file_ops kexec_efi_ops;
 
 int arch_kimage_file_post_load_cleanup(struct kimage *image);
 #define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 67b9b214d212..dd6183f353e6 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -62,7 +62,7 @@ obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_RELOCATABLE)	+= relocate.o
 
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o relocate_kernel.o
-obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o
+obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_efi.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_UNWINDER_GUESS)	+= unwind_guess.o
diff --git a/arch/loongarch/kernel/kexec_efi.c b/arch/loongarch/kernel/kexec_efi.c
new file mode 100644
index 000000000000..e02fd88cf5d0
--- /dev/null
+++ b/arch/loongarch/kernel/kexec_efi.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Load EFI vmlinux file for the kexec_file_load syscall.
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ */
+
+#define pr_fmt(fmt)	"kexec_file(EFI): " fmt
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/pe.h>
+#include <linux/string.h>
+#include <asm/byteorder.h>
+#include <asm/cpufeature.h>
+#include <asm/image.h>
+
+static int efi_kexec_probe(const char *kernel_buf, unsigned long kernel_len)
+{
+	const struct loongarch_image_header *h = (const struct loongarch_image_header *)kernel_buf;
+
+	if (!h || (kernel_len < sizeof(*h))) {
+		pr_err("No loongarch image header.\n");
+		return -EINVAL;
+	}
+
+	if (!loongarch_header_check_dos_sig(h)) {
+		pr_warn("No loongarch PE image header.\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void *efi_kexec_load(struct kimage *image,
+				char *kernel, unsigned long kernel_len,
+				char *initrd, unsigned long initrd_len,
+				char *cmdline, unsigned long cmdline_len)
+{
+	struct loongarch_image_header *h;
+	struct kexec_buf kbuf;
+	unsigned long text_offset, kernel_segment_number;
+	struct kexec_segment *kernel_segment;
+	int ret;
+
+	h = (struct loongarch_image_header *)kernel;
+	if (!h->kernel_asize)
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * Load the kernel
+	 * FIXME: Non-relocatable kernel rejected for kexec_file (require CONFIG_RELOCATABLE)
+	 */
+	kbuf.image = image;
+	kbuf.buf_max = ULONG_MAX;
+	kbuf.top_down = false;
+
+	kbuf.buffer = kernel;
+	kbuf.bufsz = kernel_len;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf.memsz = le64_to_cpu(h->kernel_asize);
+	text_offset = le64_to_cpu(h->text_offset);
+	kbuf.buf_min = text_offset;
+	kbuf.buf_align = SZ_2M;
+
+	kernel_segment_number = image->nr_segments;
+
+	/*
+	 * The location of the kernel segment may make it impossible to satisfy
+	 * the other segment requirements, so we try repeatedly to find a
+	 * location that will work.
+	 */
+	while ((ret = kexec_add_buffer(&kbuf)) == 0) {
+		/* Try to load additional data */
+		kernel_segment = &image->segment[kernel_segment_number];
+		ret = load_other_segments(image, kernel_segment->mem,
+					  kernel_segment->memsz, initrd,
+					  initrd_len, cmdline, cmdline_len);
+		if (!ret)
+			break;
+
+		/*
+		 * We couldn't find space for the other segments; erase the
+		 * kernel segment and try the next available hole.
+		 */
+		image->nr_segments -= 1;
+		kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz;
+		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	}
+
+	if (ret) {
+		pr_err("Could not find any suitable kernel location!");
+		return ERR_PTR(ret);
+	}
+
+	kernel_segment = &image->segment[kernel_segment_number];
+
+	/* Make sure the second kernel jumps to the correct "kernel_entry". */
+	image->start = kernel_segment->mem + h->kernel_entry - text_offset;
+
+	kexec_dprintk("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		      kernel_segment->mem, kbuf.bufsz,
+		      kernel_segment->memsz);
+
+	return NULL;
+}
+
+const struct kexec_file_ops kexec_efi_ops = {
+	.probe = efi_kexec_probe,
+	.load = efi_kexec_load,
+};
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 584ce9471e93..a454e9dfc339 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -21,6 +21,7 @@
 #include <asm/bootinfo.h>
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
+	&kexec_efi_ops,
 	NULL
 };
 
-- 
2.43.0

[PATCH v4 4/7] LoongArch/kexec_file: Support loading ELF binary file

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

This patch creates kexec_elf_ops to load ELF binary file for
kexec_file_load() syscall.

However, for `kbuf->memsz` and `kbuf->buf_min`, special handling is required,
and the generic `kexec_elf_load()` cannot be used directly.

$ readelf -l vmlinux
...
   Type           Offset             VirtAddr           PhysAddr
                  FileSiz            MemSiz              Flags Align
   LOAD           0x0000000000010000 0x9000000000200000 0x9000000000200000
                  0x0000000002747a00 0x000000000287a0d8  RWE 0x10000
   NOTE           0x0000000000000000 0x0000000000000000 0x0000000000000000
                  0x0000000000000000 0x0000000000000000  R      0x8

phdr->p_paddr should have been a physical address, but it is a virtual
address on the current LoongArch. This will cause kexec_file to fail
when loading the kernel and need to be converted to a physical address.

From the above MemSiz, it can be seen that 0x287a0d8 has not been aligned.
Although kexec_add_buffer() will perform PAGE_SIZE alignment on kbuf->memsz,
there is still a stampeding in the loaded kernel space and initrd space.
The initrd resolution failed when starting the second kernel.

It can be known from the link script vmlinux.lds.S that,
    BSS_SECTION(0, SZ_64K, 8)
    . = ALIGN(PECOFF_SEGMENT_ALIGN);

It needs to be aligned according to the SZ_64K size, so that after
alignment, its size is consistent with _kernel_asize.

The basic usage (vmlinux):
1) Load second kernel image:
 # kexec -s -l vmlinux --initrd=initrd.img --reuse-cmdline

2) Startup second kernel:
 # kexec -e

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/Kconfig                     |   1 +
 arch/loongarch/include/asm/kexec.h         |   1 +
 arch/loongarch/kernel/Makefile             |   2 +-
 arch/loongarch/kernel/kexec_elf.c          | 105 +++++++++++++++++++++
 arch/loongarch/kernel/machine_kexec_file.c |   1 +
 5 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/kernel/kexec_elf.c

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 490dc6eed749..bf2664ed7ce3 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -632,6 +632,7 @@ config ARCH_SELECTS_KEXEC_FILE
 	def_bool y
 	depends on KEXEC_FILE
 	select HAVE_IMA_KEXEC if IMA
+	select KEXEC_ELF
 	select RELOCATABLE
 
 config ARCH_SUPPORTS_CRASH_DUMP
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
index 34799db933fb..fecfb3015abc 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -43,6 +43,7 @@ struct kimage_arch {
 
 #ifdef CONFIG_KEXEC_FILE
 extern const struct kexec_file_ops kexec_efi_ops;
+extern const struct kexec_file_ops kexec_elf_ops;
 
 int arch_kimage_file_post_load_cleanup(struct kimage *image);
 #define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index dd6183f353e6..001924877772 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -62,7 +62,7 @@ obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 obj-$(CONFIG_RELOCATABLE)	+= relocate.o
 
 obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o relocate_kernel.o
-obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_efi.o
+obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_efi.o kexec_elf.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_UNWINDER_GUESS)	+= unwind_guess.o
diff --git a/arch/loongarch/kernel/kexec_elf.c b/arch/loongarch/kernel/kexec_elf.c
new file mode 100644
index 000000000000..175d8d935e11
--- /dev/null
+++ b/arch/loongarch/kernel/kexec_elf.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Load ELF vmlinux file for the kexec_file_load syscall.
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ */
+
+#define pr_fmt(fmt)	"kexec_file(ELF): " fmt
+
+#include <linux/elf.h>
+#include <linux/kexec.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/memblock.h>
+#include <asm/setup.h>
+
+static int loongarch_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
+			 struct kexec_elf_info *elf_info,
+			 struct kexec_buf *kbuf,
+			 unsigned long *text_offset)
+{
+	int ret = -1;
+	size_t i;
+
+	/* Read in the PT_LOAD segments. */
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		size_t size;
+		const struct elf_phdr *phdr;
+
+		phdr = &elf_info->proghdrs[i];
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		size = phdr->p_filesz;
+		if (size > phdr->p_memsz)
+			size = phdr->p_memsz;
+
+		kbuf->buffer = (void *)elf_info->buffer + phdr->p_offset;
+		kbuf->bufsz = size;
+		kbuf->buf_align = phdr->p_align;
+		*text_offset = __pa(phdr->p_paddr);
+		kbuf->buf_min = *text_offset;
+		kbuf->memsz = ALIGN(phdr->p_memsz, SZ_64K);
+		kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
+		ret = kexec_add_buffer(kbuf);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
+			    unsigned long kernel_len, char *initrd,
+			    unsigned long initrd_len, char *cmdline,
+			    unsigned long cmdline_len)
+{
+	int ret;
+	unsigned long text_offset = 0, kernel_segment_number;
+	struct elfhdr ehdr;
+	struct kexec_elf_info elf_info;
+	struct kexec_segment *kernel_segment;
+	struct kexec_buf kbuf;
+
+	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/*
+	 * Load the kernel
+	 * FIXME: Non-relocatable kernel rejected for kexec_file (require CONFIG_RELOCATABLE)
+	 */
+	kbuf.image = image;
+	kbuf.buf_max = ULONG_MAX;
+	kbuf.top_down = false;
+
+	kernel_segment_number = image->nr_segments;
+
+	ret = loongarch_kexec_elf_load(image, &ehdr, &elf_info, &kbuf, &text_offset);
+	if (ret)
+		goto out;
+
+	/* Load additional data */
+	kernel_segment = &image->segment[kernel_segment_number];
+	ret = load_other_segments(image, kernel_segment->mem, kernel_segment->memsz,
+				  initrd, initrd_len, cmdline, cmdline_len);
+	if (ret)
+		goto out;
+
+	/* Make sure the second kernel jumps to the correct "kernel_entry". */
+	image->start = kernel_segment->mem + __pa(ehdr.e_entry) - text_offset;
+
+	kexec_dprintk("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		      kernel_segment->mem, kbuf.bufsz, kernel_segment->memsz);
+
+out:
+	kexec_free_elf_info(&elf_info);
+	return ret ? ERR_PTR(ret) : NULL;
+}
+
+const struct kexec_file_ops kexec_elf_ops = {
+	.probe = kexec_elf_probe,
+	.load  = elf_kexec_load,
+};
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index a454e9dfc339..81913359b7a1 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -22,6 +22,7 @@
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 	&kexec_efi_ops,
+	&kexec_elf_ops,
 	NULL
 };
 
-- 
2.43.0

[PATCH v4 5/7] LoongArch/kexec_file: Add crash dump support

[Youling Tang]

From: Youling Tang <tangyouling@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@start" to cmdline.
- Add the "mem=size@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.

The basic usage for kdump(add the cmdline parameter crashkernel=512M
to grub.cfg):
1) Load capture kernel image(vmlinux.efi or vmlinux can also be used):
 # kexec -s -p vmlinuz.efi --initrd=initrd.img --reuse-cmdline

2) Do something to crash, like:
 # echo c > /proc/sysrq-trigger

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/kernel/machine_kexec_file.c | 116 +++++++++++++++++++++
 1 file changed, 116 insertions(+)

diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 81913359b7a1..907a3286fa0d 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -35,6 +35,82 @@ 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@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@0x%lx ",
+		elfcorehdr_sz, image->elf_load_addr);
+	*cmdline_tmplen += elfcorehdr_strlen;
+}
+
+/*
+ * Adds the "mem=size@start" command line parameter to command line, indicating the
+ * memory region the new kernel can use to boot into.
+ */
+static void cmdline_add_mem(unsigned long *cmdline_tmplen, char *modified_cmdline)
+{
+	int mem_strlen = 0;
+
+	mem_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "mem=0x%llx@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@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)
@@ -86,6 +162,46 @@ int load_other_segments(struct kimage *image,
 	/* Ensure it's null 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@start parameter to the command line */
+		cmdline_add_elfcorehdr(image, &cmdline_tmplen, modified_cmdline, headers_sz);
+
+		/* Add the mem=size@start parameter to the command line */
+		cmdline_add_mem(&cmdline_tmplen, modified_cmdline);
+	}
+#endif
+
 	/* load initrd */
 	if (initrd) {
 		kbuf.buffer = initrd;
-- 
2.43.0

[PATCH v4 6/7] LoongArch: Automatically disable kaslr when the kernel loads from kexec_file

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

Automatically disable kaslr when the kernel loads from kexec_file.

kexec_file loads the secondary kernel image to a non-linked address,
inherently providing KASLR-like randomization.

However, on LoongArch where System RAM may be non-contiguous, enabling
KASLR for the second kernel could relocate it to an invalid memory
region and cause boot failure. Thus, we disable KASLR when
"kexec_file" is detected in the command line.

To ensure compatibility with older kernels loaded via kexec_file,
this patch need be backported to stable branches.

Cc: stable@vger.kernel.org
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/kernel/relocate.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 50c469067f3a..4c097532cb88 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -140,6 +140,10 @@ static inline __init bool kaslr_disabled(void)
 	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
 		return true;
 
+	str = strstr(boot_command_line, "kexec_file");
+	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
+		return true;
+
 #ifdef CONFIG_HIBERNATION
 	str = strstr(builtin_cmdline, "nohibernate");
 	if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' '))
-- 
2.43.0

[PATCH v4 7/7] LoongArch: Enable CONFIG_KEXEC_FILE

[Youling Tang]

From: Youling Tang <tangyouling@kylinos.cn>

This patch enables config KEXEC_FILE by default in the
loongson3_defconfig, so that user-space tools like kexec-tools
can use the same as the default interface for kexec/kdump
on LoongArch.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 arch/loongarch/configs/loongson3_defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
index 34eaee0384c9..6cfea2f37cc0 100644
--- a/arch/loongarch/configs/loongson3_defconfig
+++ b/arch/loongarch/configs/loongson3_defconfig
@@ -45,6 +45,7 @@ CONFIG_EXPERT=y
 CONFIG_KALLSYMS_ALL=y
 CONFIG_PERF_EVENTS=y
 CONFIG_KEXEC=y
+CONFIG_KEXEC_FILE=y
 CONFIG_CRASH_DUMP=y
 CONFIG_LOONGARCH=y
 CONFIG_64BIT=y
-- 
2.43.0

Re: [PATCH v4 0/7] Add kexec_file support for LoongArch

[Huacai Chen]

Applied with some modifications. You may need to test whether everything is OK.
https://github.com/chenhuacai/linux/commits/loongarch-next

Huacai

On Wed, Sep 3, 2025 at 11:02 AM Youling Tang <youling.tang@linux.dev> wrote:
>
> From: Youling Tang <tangyouling@kylinos.cn>
>
> This patchset implement kexec_file_load() support on LoongArch.
>
> This patch series enables us to load the LoongArch vmlinuz.efi(pez) or
> vmlinux.efi(pei) or vmlinux(elf) by specifying its file decriptor,
> instead of user-filled buffer via kexec_load() syscall.
>
> To use kexec_file_load() system call, instead of kexec_load(), at kexec
> command, '-s' options must be specified. kexec-tools needs to apply the
> corresponding patches. These patches can be found in repository [1] and
> will be submitted to the kexec-tools community later.
>
> The basic usage of kexec_file is:
> 1) Load second kernel image:
>  # kexec -s -l vmlinuz.efi --initrd=initrd.img --reuse-cmdline
>
> 2) Startup second kernel:
>  # kexec -e
>
> For kdump:
> 1) Load capture kernel image:
>  # kexec -s -p vmlinuz.efi --initrd=initrd.img --reuse-cmdline
>
> 2) Do something to crash, like:
>  # echo c > /proc/sysrq-trigger
>
> Link:
> [1] https://github.com/tangyouling/kexec-tools/commits/main/
>
> Changelog:
>  v4:
>  * Add the character "kexec_file" to the command-line parameter.
>  * Fixed the issue where kexec_file failed to load the KASLR kernel
>    startup.
>  * Modify the member name of the loongarch_image_header structure.
>  * Modify the patch commit message.
>
>  v3:
>  * The ELF format kernel loading should not use loongarch_image_header.
>  * Separate patch2 into an infrastructure patch and an EFI support
>    patch.
>  * Adding that kexec_file cannot load non-relocation kernel comments.
>  * Some minor modifications.
>
>  v2:
>  * Merge some patches.
>  * Add support for ELF format images.
>  * Rename kexec_image.c to kexec_efi.c .
>  * When KEXEC_FILE is enabled, RELOCATABLE is selected by default.
>  * Some minor modifications.
>
> Youling Tang (7):
>   LoongArch: Add struct loongarch_image_header for kernel image
>   LoongArch: Add preparatory infrastructure for kexec_file
>   LoongArch/kexec_file: Support loading EFI binary file
>   LoongArch/kexec_file: Support loading ELF binary file
>   LoongArch/kexec_file: Add crash dump support
>   LoongArch: Automatically disable kaslr when the kernel loads from
>     kexec_file
>   LoongArch: Enable CONFIG_KEXEC_FILE
>
>  arch/loongarch/Kconfig                     |  10 +
>  arch/loongarch/configs/loongson3_defconfig |   1 +
>  arch/loongarch/include/asm/image.h         |  53 +++++
>  arch/loongarch/include/asm/kexec.h         |  13 ++
>  arch/loongarch/kernel/Makefile             |   1 +
>  arch/loongarch/kernel/kexec_efi.c          | 114 ++++++++++
>  arch/loongarch/kernel/kexec_elf.c          | 105 +++++++++
>  arch/loongarch/kernel/machine_kexec.c      |  37 ++--
>  arch/loongarch/kernel/machine_kexec_file.c | 244 +++++++++++++++++++++
>  arch/loongarch/kernel/relocate.c           |   4 +
>  10 files changed, 569 insertions(+), 13 deletions(-)
>  create mode 100644 arch/loongarch/include/asm/image.h
>  create mode 100644 arch/loongarch/kernel/kexec_efi.c
>  create mode 100644 arch/loongarch/kernel/kexec_elf.c
>  create mode 100644 arch/loongarch/kernel/machine_kexec_file.c
>
> --
> 2.43.0
>