kexec: add KEXEC_ELF

Right now powerpc provides an implementation to read elf files
with the kexec_file_load() syscall. Make that available as a public
kexec interface so it can be re-used on other architectures.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Helge Deller <deller@gmx.de>

arch/Kconfig

@@ -18,6 +18,9 @@ config KEXEC_CORE
 	select CRASH_CORE
 	bool
 
+config KEXEC_ELF
+	bool
+
 config HAVE_IMA_KEXEC
 	bool
 

arch/powerpc/Kconfig

@@ -512,6 +512,7 @@ config KEXEC_FILE
 	select KEXEC_CORE
 	select HAVE_IMA_KEXEC
 	select BUILD_BIN2C
+	select KEXEC_ELF
 	depends on PPC64
 	depends on CRYPTO=y
 	depends on CRYPTO_SHA256=y

include/linux/kexec.h

@@ -216,6 +216,30 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
 				       void **addr, unsigned long *sz);
 #endif /* CONFIG_KEXEC_FILE */
 
+#ifdef CONFIG_KEXEC_ELF
+struct kexec_elf_info {
+	/*
+	 * Where the ELF binary contents are kept.
+	 * Memory managed by the user of the struct.
+	 */
+	const char *buffer;
+
+	const struct elfhdr *ehdr;
+	const struct elf_phdr *proghdrs;
+	struct elf_shdr *sechdrs;
+};
+
+int kexec_build_elf_info(const char *buf, size_t len, struct elfhdr *ehdr,
+			       struct kexec_elf_info *elf_info);
+
+int kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
+			 struct kexec_elf_info *elf_info,
+			 struct kexec_buf *kbuf,
+			 unsigned long *lowest_load_addr);
+
+void kexec_free_elf_info(struct kexec_elf_info *elf_info);
+int kexec_elf_probe(const char *buf, unsigned long len);
+#endif
 struct kimage {
 	kimage_entry_t head;
 	kimage_entry_t *entry;

kernel/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
 obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
 obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
+obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
 obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup/