s390/kexec_file: Add image loader

Add an image loader for kexec_file_load. For simplicity first skip crash
support. The functions defined in machine_kexec_file will later be shared
with the ELF loader.

Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/kexec.h

@@ -46,4 +46,26 @@
 static inline void crash_setup_regs(struct pt_regs *newregs,
 					struct pt_regs *oldregs) { }
 
+struct kimage;
+struct s390_load_data {
+	/* Pointer to the kernel buffer. Used to register cmdline etc.. */
+	void *kernel_buf;
+
+	/* Total size of loaded segments in memory. Used as an offset. */
+	size_t memsz;
+
+	/* Load address of initrd. Used to register INITRD_START in kernel. */
+	unsigned long initrd_load_addr;
+};
+
+int kexec_file_add_purgatory(struct kimage *image,
+			     struct s390_load_data *data);
+int kexec_file_add_initrd(struct kimage *image,
+			  struct s390_load_data *data,
+			  char *initrd, unsigned long initrd_len);
+int *kexec_file_update_kernel(struct kimage *iamge,
+			      struct s390_load_data *data);
+
+extern const struct kexec_file_ops s390_kexec_image_ops;
+
 #endif /*_S390_KEXEC_H */

arch/s390/kernel/Makefile

@@ -82,7 +82,7 @@ obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
 
-obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o
+obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file.o kexec_image.o
 
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf.o perf_cpum_sf.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf_events.o perf_regs.o

arch/s390/kernel/kexec_image.c

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Image loader for kexec_file_load system call.
+ *
+ * Copyright IBM Corp. 2018
+ *
+ * Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <asm/setup.h>
+
+static int kexec_file_add_image_kernel(struct kimage *image,
+				       struct s390_load_data *data,
+				       char *kernel, unsigned long kernel_len)
+{
+	struct kexec_buf buf;
+	int ret;
+
+	buf.image = image;
+
+	buf.buffer = kernel + STARTUP_NORMAL_OFFSET;
+	buf.bufsz = kernel_len - STARTUP_NORMAL_OFFSET;
+
+	buf.mem = STARTUP_NORMAL_OFFSET;
+	buf.memsz = buf.bufsz;
+
+	ret = kexec_add_buffer(&buf);
+
+	data->kernel_buf = kernel;
+	data->memsz += buf.memsz + STARTUP_NORMAL_OFFSET;
+
+	return ret;
+}
+
+static void *s390_image_load(struct kimage *image,
+			     char *kernel, unsigned long kernel_len,
+			     char *initrd, unsigned long initrd_len,
+			     char *cmdline, unsigned long cmdline_len)
+{
+	struct s390_load_data data = {0};
+	int ret;
+
+	/* We don't support crash kernels yet. */
+	if (image->type == KEXEC_TYPE_CRASH)
+		return ERR_PTR(-ENOTSUPP);
+
+	ret = kexec_file_add_image_kernel(image, &data, kernel, kernel_len);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (initrd) {
+		ret = kexec_file_add_initrd(image, &data, initrd, initrd_len);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	ret = kexec_file_add_purgatory(image, &data);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return kexec_file_update_kernel(image, &data);
+}
+
+static int s390_image_probe(const char *buf, unsigned long len)
+{
+	/* Can't reliably tell if an image is valid.  Therefore give the
+	 * user whatever he wants.
+	 */
+	return 0;
+}
+
+const struct kexec_file_ops s390_kexec_image_ops = {
+	.probe = s390_image_probe,
+	.load = s390_image_load,
+};

arch/s390/kernel/machine_kexec_file.c

@@ -12,9 +12,84 @@
 #include <asm/setup.h>
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
+	&s390_kexec_image_ops,
 	NULL,
 };
 
+int *kexec_file_update_kernel(struct kimage *image,
+			      struct s390_load_data *data)
+{
+	unsigned long *loc;
+
+	if (image->cmdline_buf_len >= ARCH_COMMAND_LINE_SIZE)
+		return ERR_PTR(-EINVAL);
+
+	if (image->cmdline_buf_len)
+		memcpy(data->kernel_buf + COMMAND_LINE_OFFSET,
+		       image->cmdline_buf, image->cmdline_buf_len);
+
+	if (image->initrd_buf) {
+		loc = (unsigned long *)(data->kernel_buf + INITRD_START_OFFSET);
+		*loc = data->initrd_load_addr;
+
+		loc = (unsigned long *)(data->kernel_buf + INITRD_SIZE_OFFSET);
+		*loc = image->initrd_buf_len;
+	}
+
+	return NULL;
+}
+
+static int kexec_file_update_purgatory(struct kimage *image)
+{
+	u64 entry, type;
+	int ret;
+
+	entry = STARTUP_NORMAL_OFFSET;
+	ret = kexec_purgatory_get_set_symbol(image, "kernel_entry", &entry,
+					     sizeof(entry), false);
+	return ret;
+}
+
+int kexec_file_add_purgatory(struct kimage *image, struct s390_load_data *data)
+{
+	struct kexec_buf buf;
+	int ret;
+
+	buf.image = image;
+
+	data->memsz = ALIGN(data->memsz, PAGE_SIZE);
+	buf.mem = data->memsz;
+
+	ret = kexec_load_purgatory(image, &buf);
+	if (ret)
+		return ret;
+
+	ret = kexec_file_update_purgatory(image);
+	return ret;
+}
+
+int kexec_file_add_initrd(struct kimage *image, struct s390_load_data *data,
+			  char *initrd, unsigned long initrd_len)
+{
+	struct kexec_buf buf;
+	int ret;
+
+	buf.image = image;
+
+	buf.buffer = initrd;
+	buf.bufsz = initrd_len;
+
+	data->memsz = ALIGN(data->memsz, PAGE_SIZE);
+	buf.mem = data->memsz;
+	buf.memsz = buf.bufsz;
+
+	data->initrd_load_addr = buf.mem;
+	data->memsz += buf.memsz;
+
+	ret = kexec_add_buffer(&buf);
+	return ret;
+}
+
 /*
  * The kernel is loaded to a fixed location. Turn off kexec_locate_mem_hole
  * and provide kbuf->mem by hand.