kernel/kexec_file.c: allow archs to set purgatory load address

For s390 new kernels are loaded to fixed addresses in memory before they
are booted.  With the current code this is a problem as it assumes the
kernel will be loaded to an 'arbitrary' address.  In particular,
kexec_locate_mem_hole searches for a large enough memory region and sets
the load address (kexec_bufer->mem) to it.

Luckily there is a simple workaround for this problem.  By returning 1
in arch_kexec_walk_mem, kexec_locate_mem_hole is turned off.  This
allows the architecture to set kbuf->mem by hand.  While the trick works
fine for the kernel it does not for the purgatory as here the
architectures don't have access to its kexec_buffer.

Give architectures access to the purgatories kexec_buffer by changing
kexec_load_purgatory to take a pointer to it.  With this change
architectures have access to the buffer and can edit it as they need.

A nice side effect of this change is that we can get rid of the
purgatory_info->purgatory_load_address field.  As now the information
stored there can directly be accessed from kbuf->mem.

Link: http://lkml.kernel.org/r/20180321112751.22196-11-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 11 deletions

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 0e389b9b7722..9e4e638fb505 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -114,9 +114,6 @@ struct purgatory_info {
 	 * relocation. This memory can be freed post image load.
 	 */
 	void *purgatory_buf;
-
-	/* Address where purgatory is finally loaded and is executed from */
-	unsigned long purgatory_load_addr;
 };
 
 struct kimage;
@@ -171,6 +168,12 @@ struct kexec_buf {
 	bool top_down;
 };
 
+int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf);
+int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
+				   void *buf, unsigned int size,
+				   bool get_value);
+void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name);
+
 int __weak arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 					    Elf_Shdr *section,
 					    const Elf_Shdr *relsec,
@@ -266,14 +269,6 @@ extern void machine_kexec_cleanup(struct kimage *image);
 extern int kernel_kexec(void);
 extern struct page *kimage_alloc_control_pages(struct kimage *image,
 						unsigned int order);
-extern int kexec_load_purgatory(struct kimage *image, unsigned long min,
-				unsigned long max, int top_down,
-				unsigned long *load_addr);
-extern int kexec_purgatory_get_set_symbol(struct kimage *image,
-					  const char *name, void *buf,
-					  unsigned int size, bool get_value);
-extern void *kexec_purgatory_get_symbol_addr(struct kimage *image,
-					     const char *name);
 extern void __crash_kexec(struct pt_regs *);
 extern void crash_kexec(struct pt_regs *);
 int kexec_should_crash(struct task_struct *);