RISC-V: Add kexec_file support

This patch adds support for kexec_file on RISC-V. I tested it on riscv64
QEMU with busybear-linux and single core along with the OpenSBI firmware
fw_jump.bin for generic platform.

On SMP system, it depends on CONFIG_{HOTPLUG_CPU, RISCV_SBI} to
resume/stop hart through OpenSBI firmware, it also needs a OpenSBI that
support the HSM extension.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Li Zhengyu <lizhengyu3@huawei.com>
Link: https://lore.kernel.org/r/20220408100914.150110-4-lizhengyu3@huawei.com
[Palmer: Make 64-bit only]
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -383,6 +383,20 @@ config KEXEC
 
 	  The name comes from the similarity to the exec system call.
 
+config KEXEC_FILE
+	bool "kexec file based systmem call"
+	select KEXEC_CORE
+	select KEXEC_ELF
+	select HAVE_IMA_KEXEC if IMA
+	depends on 64BIT
+	help
+	  This is new version of kexec system call. This system call is
+	  file based and takes file descriptors as system call argument
+	  for kernel and initramfs as opposed to list of segments as
+	  accepted by previous system call.
+
+	  If you don't know what to do here, say Y.
+
 config CRASH_DUMP
 	bool "Build kdump crash kernel"
 	help

arch/riscv/include/asm/kexec.h

@@ -53,4 +53,8 @@ typedef void (*riscv_kexec_method)(unsigned long first_ind_entry,
 
 extern riscv_kexec_method riscv_kexec_norelocate;
 
+#ifdef CONFIG_KEXEC_FILE
+extern const struct kexec_file_ops elf_kexec_ops;
+#endif
+
 #endif

arch/riscv/kernel/Makefile

@@ -64,6 +64,7 @@ endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_KEXEC)		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
+obj-$(CONFIG_KEXEC_FILE)	+= elf_kexec.o machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o

arch/riscv/kernel/elf_kexec.c

@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Load ELF vmlinux file for the kexec_file_load syscall.
+ *
+ * Copyright (C) 2021 Huawei Technologies Co, Ltd.
+ *
+ * Author: Liao Chang (liaochang1@huawei.com)
+ *
+ * Based on kexec-tools' kexec-elf-riscv.c, heavily modified
+ * for kernel.
+ */
+
+#define pr_fmt(fmt)	"kexec_image: " fmt
+
+#include <linux/elf.h>
+#include <linux/kexec.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/libfdt.h>
+#include <linux/types.h>
+
+static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
+				struct kexec_elf_info *elf_info, unsigned long old_pbase,
+				unsigned long new_pbase)
+{
+	int i;
+	int ret = 0;
+	size_t size;
+	struct kexec_buf kbuf;
+	const struct elf_phdr *phdr;
+
+	kbuf.image = image;
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		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;
+		kbuf.mem = phdr->p_paddr - old_pbase + new_pbase;
+		kbuf.memsz = phdr->p_memsz;
+		kbuf.top_down = false;
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+/*
+ * Go through the available phsyical memory regions and find one that hold
+ * an image of the specified size.
+ */
+static int elf_find_pbase(struct kimage *image, unsigned long kernel_len,
+			  struct elfhdr *ehdr, struct kexec_elf_info *elf_info,
+			  unsigned long *old_pbase, unsigned long *new_pbase)
+{
+	int i;
+	int ret;
+	struct kexec_buf kbuf;
+	const struct elf_phdr *phdr;
+	unsigned long lowest_paddr = ULONG_MAX;
+	unsigned long lowest_vaddr = ULONG_MAX;
+
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		phdr = &elf_info->proghdrs[i];
+		if (phdr->p_type != PT_LOAD)
+			continue;
+
+		if (lowest_paddr > phdr->p_paddr)
+			lowest_paddr = phdr->p_paddr;
+
+		if (lowest_vaddr > phdr->p_vaddr)
+			lowest_vaddr = phdr->p_vaddr;
+	}
+
+	kbuf.image = image;
+	kbuf.buf_min = lowest_paddr;
+	kbuf.buf_max = ULONG_MAX;
+	kbuf.buf_align = PAGE_SIZE;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf.memsz = ALIGN(kernel_len, PAGE_SIZE);
+	kbuf.top_down = false;
+	ret = arch_kexec_locate_mem_hole(&kbuf);
+	if (!ret) {
+		*old_pbase = lowest_paddr;
+		*new_pbase = kbuf.mem;
+		image->start = ehdr->e_entry - lowest_vaddr + kbuf.mem;
+	}
+	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 old_kernel_pbase = ULONG_MAX;
+	unsigned long new_kernel_pbase = 0UL;
+	unsigned long initrd_pbase = 0UL;
+	void *fdt;
+	struct elfhdr ehdr;
+	struct kexec_buf kbuf;
+	struct kexec_elf_info elf_info;
+
+	ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
+	if (ret)
+		return ERR_PTR(ret);
+
+	ret = elf_find_pbase(image, kernel_len, &ehdr, &elf_info,
+			     &old_kernel_pbase, &new_kernel_pbase);
+	if (ret)
+		goto out;
+	pr_notice("The entry point of kernel at 0x%lx\n", image->start);
+
+	/* Add the kernel binary to the image */
+	ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
+				   old_kernel_pbase, new_kernel_pbase);
+	if (ret)
+		goto out;
+
+	kbuf.image = image;
+	kbuf.buf_min = new_kernel_pbase + kernel_len;
+	kbuf.buf_max = ULONG_MAX;
+	/* Add the initrd to the image */
+	if (initrd != NULL) {
+		kbuf.buffer = initrd;
+		kbuf.bufsz = kbuf.memsz = initrd_len;
+		kbuf.buf_align = PAGE_SIZE;
+		kbuf.top_down = false;
+		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+		ret = kexec_add_buffer(&kbuf);
+		if (ret)
+			goto out;
+		initrd_pbase = kbuf.mem;
+		pr_notice("Loaded initrd at 0x%lx\n", initrd_pbase);
+	}
+
+	/* Add the DTB to the image */
+	fdt = of_kexec_alloc_and_setup_fdt(image, initrd_pbase,
+					   initrd_len, cmdline, 0);
+	if (!fdt) {
+		pr_err("Error setting up the new device tree.\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	fdt_pack(fdt);
+	kbuf.buffer = fdt;
+	kbuf.bufsz = kbuf.memsz = fdt_totalsize(fdt);
+	kbuf.buf_align = PAGE_SIZE;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf.top_down = true;
+	ret = kexec_add_buffer(&kbuf);
+	if (ret) {
+		pr_err("Error add DTB kbuf ret=%d\n", ret);
+		goto out_free_fdt;
+	}
+	pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
+	goto out;
+
+out_free_fdt:
+	kvfree(fdt);
+out:
+	kexec_free_elf_info(&elf_info);
+	return ret ? ERR_PTR(ret) : NULL;
+}
+
+const struct kexec_file_ops elf_kexec_ops = {
+	.probe = kexec_elf_probe,
+	.load  = elf_kexec_load,
+};

arch/riscv/kernel/machine_kexec_file.c

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_file for riscv, use vmlinux as the dump-capture kernel image.
+ *
+ * Copyright (C) 2021 Huawei Technologies Co, Ltd.
+ *
+ * Author: Liao Chang (liaochang1@huawei.com)
+ */
+#include <linux/kexec.h>
+
+const struct kexec_file_ops * const kexec_file_loaders[] = {
+	&elf_kexec_ops,
+	NULL
+};