[PATCH v3 0/6] Add kexec_file support for LoongArch

[PATCH v3 0/6] 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:
 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 (6):
  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: Enable CONFIG_KEXEC_FILE

 arch/loongarch/Kconfig                     |  10 +
 arch/loongarch/configs/loongson3_defconfig |   1 +
 arch/loongarch/include/asm/image.h         |  57 +++++
 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 | 235 +++++++++++++++++++++
 9 files changed, 560 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 v3 1/6] 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 | 40 ++++++++++++++++++++++++++++++
 1 file changed, 40 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..1f090736e71d
--- /dev/null
+++ b/arch/loongarch/include/asm/image.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * LoongArch binary image header.
+ *
+ * Author: Youling Tang <tangyouling@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ *
+ * Most code is derived from LoongArch port of kexec-tools
+ */
+
+#ifndef __ASM_IMAGE_H
+#define __ASM_IMAGE_H
+#ifndef __ASSEMBLY__
+
+/**
+ * struct loongarch_image_header
+ *
+ * @pe_sig: Optional PE format 'MZ' signature.
+ * @reserved_1: Reserved.
+ * @kernel_entry: Kernel image entry pointer.
+ * @image_size: An estimated size of the memory image size in LSB byte order.
+ * @text_offset: The image load offset in LSB byte order.
+ * @reserved_2: Reserved.
+ * @reserved_3: Reserved.
+ * @pe_header: Optional offset to a PE format header.
+ **/
+
+struct loongarch_image_header {
+	uint8_t pe_sig[2];
+	uint16_t reserved_1[3];
+	uint64_t kernel_entry;
+	uint64_t image_size;
+	uint64_t text_offset;
+	uint64_t reserved_2[3];
+	uint32_t reserved_3;
+	uint32_t pe_header;
+};
+
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_IMAGE_H */
-- 
2.43.0

[PATCH v3 2/6] 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'.

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 | 116 +++++++++++++++++++++
 5 files changed, 161 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..7fe3f182a632
--- /dev/null
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -0,0 +1,116 @@
+// 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;
+}
+
+/*
+ * 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;
+
+	/* Ensure it's nul 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 cmdline 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 v3 3/6] 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.

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 1f090736e71d..655d5836c4e8 100644
--- a/arch/loongarch/include/asm/image.h
+++ b/arch/loongarch/include/asm/image.h
@@ -36,5 +36,22 @@ struct loongarch_image_header {
 	uint32_t pe_header;
 };
 
+static const uint8_t loongarch_image_pe_sig[2] = {'M', 'Z'};
+
+/**
+ * loongarch_header_check_pe_sig - Helper to check the loongarch image header.
+ *
+ * Returns non-zero if 'MZ' signature is found.
+ */
+
+static inline int loongarch_header_check_pe_sig(const struct loongarch_image_header *h)
+{
+	if (!h)
+		return 0;
+
+	return (h->pe_sig[0] == loongarch_image_pe_sig[0]
+		&& h->pe_sig[1] == loongarch_image_pe_sig[1]);
+}
+
 #endif /* __ASSEMBLY__ */
 #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..5e2d424548d9
--- /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_pe_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->image_size)
+		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->image_size);
+	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 7fe3f182a632..a713acf32db8 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 v3 4/6] 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.

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 a713acf32db8..dc6e37457559 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 v3 5/6] 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.

Signed-off-by: Youling Tang <tangyouling@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@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(struct kimage *image, 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)
@@ -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@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(image, &cmdline_tmplen, modified_cmdline);
+	}
+#endif
+
 	/* load initrd */
 	if (initrd) {
 		kbuf.buffer = initrd;
-- 
2.43.0

[PATCH v3 6/6] 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 v3 1/6] LoongArch: Add struct loongarch_image_header for kernel image

[Huacai Chen]

Hi, Youling,

On Tue, Aug 26, 2025 at 9:18 AM Youling Tang <youling.tang@linux.dev> wrote:
>
> 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 | 40 ++++++++++++++++++++++++++++++
>  1 file changed, 40 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..1f090736e71d
> --- /dev/null
> +++ b/arch/loongarch/include/asm/image.h
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * LoongArch binary image header.
> + *
> + * Author: Youling Tang <tangyouling@kylinos.cn>
> + * Copyright (C) 2025 KylinSoft Corporation.
> + *
> + * Most code is derived from LoongArch port of kexec-tools
> + */
> +
> +#ifndef __ASM_IMAGE_H
> +#define __ASM_IMAGE_H
> +#ifndef __ASSEMBLY__

__ASSEMBLY__ is replaced by __ASSEMBLER__ now.

> +
> +/**
> + * struct loongarch_image_header
> + *
> + * @pe_sig: Optional PE format 'MZ' signature.
> + * @reserved_1: Reserved.
> + * @kernel_entry: Kernel image entry pointer.
> + * @image_size: An estimated size of the memory image size in LSB byte order.
> + * @text_offset: The image load offset in LSB byte order.
> + * @reserved_2: Reserved.
> + * @reserved_3: Reserved.
> + * @pe_header: Optional offset to a PE format header.
> + **/
> +
> +struct loongarch_image_header {
> +       uint8_t pe_sig[2];
Use dos_sig is better.

> +       uint16_t reserved_1[3];
Use padding_1[3] is better.

> +       uint64_t kernel_entry;
> +       uint64_t image_size;
Use kernel_asize to keep consistency with head.S.

> +       uint64_t text_offset;
> +       uint64_t reserved_2[3];
> +       uint32_t reserved_3;
Just use uint32_t reserved_2[7] here?


Huacai

> +       uint32_t pe_header;
> +};
> +
> +#endif /* __ASSEMBLY__ */
> +#endif /* __ASM_IMAGE_H */
> --
> 2.43.0
>