[PATCH v2 1/3] LoongArch: Add kexec support

[Youling Tang]

Add three new files, kexec.h, machine_kexec.c and relocate_kernel.S to the
LoongArch architecture that add support for the kexec re-boot mechanis
(CONFIG_KEXEC) on LoongArch platforms.

Supports loading vmlinux (vmlinux.elf) in ELF format and vmlinux.efi in
PE format.

I tested this on  LoongArch 3A5000 machine and works as expected,

 $ sudo kexec -l /boot/vmlinux.efi --reuse-cmdline
 $ sudo kexec -e

Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
---
 arch/loongarch/Kconfig                  |  11 ++
 arch/loongarch/include/asm/kexec.h      |  58 ++++++++
 arch/loongarch/kernel/Makefile          |   2 +
 arch/loongarch/kernel/head.S            |   7 +-
 arch/loongarch/kernel/machine_kexec.c   | 188 ++++++++++++++++++++++++
 arch/loongarch/kernel/relocate_kernel.S | 106 +++++++++++++
 6 files changed, 371 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/include/asm/kexec.h
 create mode 100644 arch/loongarch/kernel/machine_kexec.c
 create mode 100644 arch/loongarch/kernel/relocate_kernel.S

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 9b1f2ab878e9..08e063aaf847 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -422,6 +422,17 @@ config ARCH_IOREMAP
 	  protection support. However, you can enable LoongArch DMW-based
 	  ioremap() for better performance.
 
+config KEXEC
+	bool "Kexec system call"
+	select KEXEC_CORE
+	help
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel.  It is like a reboot
+	  but it is independent of the system firmware.   And like a reboot
+	  you can start any kernel with it, not just Linux.
+
+	  The name comes from the similarity to the exec system call.
+
 config SECCOMP
 	bool "Enable seccomp to safely compute untrusted bytecode"
 	depends on PROC_FS
diff --git a/arch/loongarch/include/asm/kexec.h b/arch/loongarch/include/asm/kexec.h
new file mode 100644
index 000000000000..f23506725e00
--- /dev/null
+++ b/arch/loongarch/include/asm/kexec.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * kexec.h for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef _ASM_KEXEC_H
+#define _ASM_KEXEC_H
+
+#include <asm/stacktrace.h>
+#include <asm/page.h>
+
+/* Maximum physical address we can use pages from */
+#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
+/* Maximum address we can reach in physical address mode */
+#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
+ /* Maximum address we can use for the control code buffer */
+#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
+
+/* Reserve a page for the control code buffer */
+#define KEXEC_CONTROL_PAGE_SIZE PAGE_SIZE
+
+/* The native architecture */
+#define KEXEC_ARCH KEXEC_ARCH_LOONGARCH
+
+static inline void crash_setup_regs(struct pt_regs *newregs,
+				    struct pt_regs *oldregs)
+{
+	if (oldregs)
+		memcpy(newregs, oldregs, sizeof(*newregs));
+	else
+		prepare_frametrace(newregs);
+}
+
+#define ARCH_HAS_KIMAGE_ARCH
+
+struct kimage_arch {
+	unsigned long boot_flag;
+	unsigned long fdt_addr;
+};
+
+typedef void (*do_kexec_t)(unsigned long boot_flag,
+			   unsigned long fdt_addr,
+			   unsigned long first_ind_entry,
+			   unsigned long jump_addr);
+
+struct kimage;
+extern const unsigned char relocate_new_kernel[];
+extern const size_t relocate_new_kernel_size;
+extern void kexec_reboot(void);
+
+#ifdef CONFIG_SMP
+extern atomic_t kexec_ready_to_reboot;
+extern const unsigned char kexec_smp_wait[];
+#endif
+
+#endif /* !_ASM_KEXEC_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 7225916dd378..17dc8ce6b5ce 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -17,6 +17,8 @@ obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o
 obj-$(CONFIG_MODULES)		+= module.o module-sections.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 
+obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
+
 obj-$(CONFIG_PROC_FS)		+= proc.o
 
 obj-$(CONFIG_SMP)		+= smp.o
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index eb3f641d5915..0f786d670e66 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -20,7 +20,12 @@
 
 _head:
 	.word	MZ_MAGIC		/* "MZ", MS-DOS header */
-	.org	0x3c			/* 0x04 ~ 0x3b reserved */
+	.org	0x8
+	.quad	0			/* Image load offset from start of RAM */
+	.dword	_end - _text		/* Effective size of kernel image */
+	.quad	0
+	.dword	kernel_entry		/* Kernel entry point */
+	.org	0x3c			/* 0x28 ~ 0x3b reserved */
 	.long	pe_header - _head	/* Offset to the PE header */
 
 pe_header:
diff --git a/arch/loongarch/kernel/machine_kexec.c b/arch/loongarch/kernel/machine_kexec.c
new file mode 100644
index 000000000000..7b3fea506c6d
--- /dev/null
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * machine_kexec.c for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#include <linux/compiler.h>
+#include <linux/cpu.h>
+#include <linux/kexec.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/libfdt.h>
+#include <linux/of_fdt.h>
+
+#include <asm/bootinfo.h>
+#include <asm/cacheflush.h>
+#include <asm/page.h>
+
+/* 0x100000 ~ 0x200000 is safe */
+#define KEXEC_CTRL_CODE	TO_CACHE(0x100000UL)
+#define KEXEC_BLOB_ADDR	TO_CACHE(0x108000UL)
+
+static unsigned long reboot_code_buffer;
+
+#ifdef CONFIG_SMP
+static void (*relocated_kexec_smp_wait)(void *);
+atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0);
+#endif
+
+static unsigned long jump_addr;
+static unsigned long first_ind_entry;
+static unsigned long boot_flag;
+static unsigned long fdt_addr;
+
+static void kexec_image_info(const struct kimage *kimage)
+{
+	unsigned long i;
+
+	pr_debug("kexec kimage info:\n");
+	pr_debug("\ttype:        %d\n", kimage->type);
+	pr_debug("\tstart:       %lx\n", kimage->start);
+	pr_debug("\thead:        %lx\n", kimage->head);
+	pr_debug("\tnr_segments: %lu\n", kimage->nr_segments);
+
+	for (i = 0; i < kimage->nr_segments; i++) {
+		pr_debug("\t    segment[%lu]: %016lx - %016lx", i,
+			kimage->segment[i].mem,
+			kimage->segment[i].mem + kimage->segment[i].memsz);
+		pr_debug("\t\t0x%lx bytes, %lu pages\n",
+			(unsigned long)kimage->segment[i].memsz,
+			(unsigned long)kimage->segment[i].memsz /  PAGE_SIZE);
+	}
+}
+
+int machine_kexec_prepare(struct kimage *kimage)
+{
+	int i;
+	void *dtb = (void *)KEXEC_BLOB_ADDR;
+
+	kexec_image_info(kimage);
+
+	/* Find the Flattened Device Tree */
+	for (i = 0; i < kimage->nr_segments; i++) {
+		if (!fdt_check_header(kimage->segment[i].buf)) {
+			memcpy(dtb, kimage->segment[i].buf, SZ_64K);
+			kimage->arch.boot_flag = fw_arg0;
+			kimage->arch.fdt_addr = (unsigned long) dtb;
+			break;
+		}
+		continue;
+	}
+
+	/* kexec need a safe page to save reboot_code_buffer */
+	kimage->control_code_page = virt_to_page((void *)KEXEC_CTRL_CODE);
+
+	reboot_code_buffer =
+	  (unsigned long)page_address(kimage->control_code_page);
+	memcpy((void *)reboot_code_buffer, relocate_new_kernel,
+	       relocate_new_kernel_size);
+
+#ifdef CONFIG_SMP
+	/* All secondary cpus now may jump to kexec_smp_wait cycle */
+	relocated_kexec_smp_wait = reboot_code_buffer +
+		(void *)(kexec_smp_wait - relocate_new_kernel);
+#endif
+
+	return 0;
+}
+
+void machine_kexec_cleanup(struct kimage *kimage)
+{
+}
+
+void kexec_reboot(void)
+{
+	do_kexec_t do_kexec = NULL;
+
+#ifdef CONFIG_SMP
+	/* All secondary cpus go to kexec_smp_wait */
+	if (smp_processor_id() > 0) {
+		relocated_kexec_smp_wait(NULL);
+		unreachable();
+	}
+#endif
+
+	do_kexec = (void *)reboot_code_buffer;
+	do_kexec(boot_flag, fdt_addr, first_ind_entry, jump_addr);
+
+	unreachable();
+}
+
+
+#ifdef CONFIG_SMP
+static void kexec_shutdown_secondary(void *)
+{
+	local_irq_disable();
+	while (!atomic_read(&kexec_ready_to_reboot))
+		cpu_relax();
+
+	kexec_reboot();
+}
+#endif
+
+void machine_crash_shutdown(struct pt_regs *regs)
+{
+}
+
+void machine_shutdown(void)
+{
+#ifdef CONFIG_SMP
+	smp_call_function(kexec_shutdown_secondary, NULL, 0);
+#endif
+}
+
+void machine_kexec(struct kimage *image)
+{
+	unsigned long entry;
+	unsigned long *ptr;
+	struct kimage_arch *internal = &image->arch;
+
+	boot_flag = internal->boot_flag;
+	fdt_addr = internal->fdt_addr;
+
+	jump_addr = (unsigned long)phys_to_virt(image->start);
+
+	first_ind_entry = (unsigned long)phys_to_virt(image->head & PAGE_MASK);
+
+	/*
+	 * The generic kexec code builds a page list with physical
+	 * addresses. they are directly accessible through XKPRANGE
+	 * hence the phys_to_virt() call.
+	 */
+	for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE);
+	     ptr = (entry & IND_INDIRECTION) ?
+	       phys_to_virt(entry & PAGE_MASK) : ptr + 1) {
+		if (*ptr & IND_SOURCE || *ptr & IND_INDIRECTION ||
+		    *ptr & IND_DESTINATION)
+			*ptr = (unsigned long) phys_to_virt(*ptr);
+	}
+
+	/* Mark offline before disabling local irq. */
+	set_cpu_online(smp_processor_id(), false);
+
+	/* we do not want to be bothered. */
+	local_irq_disable();
+
+	pr_notice("Will call new kernel at %lx\n", jump_addr);
+	pr_notice("FDT image at %lx\n", fdt_addr);
+	pr_notice("Bye ...\n");
+
+	/* Make reboot code buffer available to the boot CPU. */
+	flush_cache_all();
+
+#ifdef CONFIG_SMP
+	atomic_set(&kexec_ready_to_reboot, 1);
+#endif
+
+	/*
+	 * We know we were online, and there will be no incoming IPIs at
+	 * this point.
+	 */
+	set_cpu_online(smp_processor_id(), true);
+
+	/* Ensure remote CPUs observe that we're online before rebooting. */
+	smp_mb__after_atomic();
+
+	kexec_reboot();
+}
diff --git a/arch/loongarch/kernel/relocate_kernel.S b/arch/loongarch/kernel/relocate_kernel.S
new file mode 100644
index 000000000000..05a0c1ccfab6
--- /dev/null
+++ b/arch/loongarch/kernel/relocate_kernel.S
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * relocate_kernel.S for kexec
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/kexec.h>
+
+#include <asm/asm.h>
+#include <asm/asmmacro.h>
+#include <asm/regdef.h>
+#include <asm/loongarch.h>
+#include <asm/stackframe.h>
+#include <asm/addrspace.h>
+
+SYM_CODE_START(relocate_new_kernel)
+	/*
+	 * s0: Boot flag passed to the new kernel
+	 * s1: Virt address of the FDT image
+	 * s2: Pointer to the current entry
+	 * s3: Virt address to jump to after relocation
+	 */
+	move		s0, a0
+	move		s1, a1
+	move		s2, a2
+	move		s3, a3
+
+process_entry:
+	PTR_L		s4, s2, 0
+	PTR_ADDI	s2, s2, SZREG
+
+	/* destination page */
+	andi		s5, s4, IND_DESTINATION
+	beqz		s5, 1f
+	li.w		t0, ~0x1
+	and		s6, s4, t0	/* store destination addr in s6 */
+	b		process_entry
+
+1:
+	/* indirection page, update s2	*/
+	andi		s5, s4, IND_INDIRECTION
+	beqz		s5, 1f
+	li.w		t0, ~0x2
+	and		s2, s4, t0
+	b		process_entry
+
+1:
+	/* done page */
+	andi		s5, s4, IND_DONE
+	beqz		s5, 1f
+	b		done
+1:
+	/* source page */
+	andi		s5, s4, IND_SOURCE
+	beqz		s5, process_entry
+	li.w		t0, ~0x8
+	and		s4, s4, t0
+	li.w		s8, (1 << _PAGE_SHIFT) / SZREG
+
+copy_word:
+	/* copy page word by word */
+	REG_L		s7, s4, 0
+	REG_S		s7, s6, 0
+	PTR_ADDI	s6, s6, SZREG
+	PTR_ADDI	s4, s4, SZREG
+	LONG_ADDI	s8, s8, -1
+	beqz		s8, process_entry
+	b		copy_word
+	b		process_entry
+
+done:
+	ibar		0
+	dbar		0
+
+	move		a0, s0
+	move		a1, s1
+	/* jump to the new kernel */
+	jr		s3
+SYM_CODE_END(relocate_new_kernel)
+
+#ifdef CONFIG_SMP
+/*
+ * Other CPUs should wait until code is relocated and
+ * then start at entry (?) point.
+ */
+SYM_CODE_START(kexec_smp_wait)
+1:	li.w		t0, 0x100			/* wait for init loop */
+2:	addi.w		t0, t0, -1			/* limit mailbox access */
+	bnez		t0, 2b
+	li.w		t1, LOONGARCH_IOCSR_MBUF0
+	iocsrrd.w	s1, t1				/* check PC as an indicator */
+	beqz		s1, 1b
+	iocsrrd.d	s1, t1				/* get PC via mailbox */
+
+	li.d		t0, CACHE_BASE
+	or		s1, s1, t0			/* s1 = TO_CACHE(s1) */
+	jr		s1				/* jump to initial PC */
+SYM_CODE_END(kexec_smp_wait)
+#endif
+
+relocate_new_kernel_end:
+
+SYM_DATA_START(relocate_new_kernel_size)
+	PTR		relocate_new_kernel_end - relocate_new_kernel
+SYM_DATA_END(relocate_new_kernel_size)
-- 
2.36.0