kexec_file: Allow archs to handle special regions while locating memory hole

Some architectures may have special memory regions, within the given
memory range, which can't be used for the buffer in a kexec segment.
Implement weak arch_kexec_locate_mem_hole() definition which arch code
may override, to take care of special regions, while trying to locate
a memory hole.

Also, add the missing declarations for arch overridable functions and
and drop the __weak descriptors in the declarations to avoid non-weak
definitions from becoming weak.

Signed-off-by: Hari Bathini <[e-mail]>
Tested-by: Pingfan Liu <[e-mail]>
Reviewed-by: Thiago Jung Bauermann <[e-mail]>
Acked-by: Dave Young <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/159602273603.575379.17665852963340380839.stgit@hbathini

include/linux/kexec.h

···
 				   bool get_value);
 void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name);
 
-int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
-					 unsigned long buf_len);
-void * __weak arch_kexec_kernel_image_load(struct kimage *image);
-int __weak arch_kexec_apply_relocations_add(struct purgatory_info *pi,
-					    Elf_Shdr *section,
-					    const Elf_Shdr *relsec,
-					    const Elf_Shdr *symtab);
-int __weak arch_kexec_apply_relocations(struct purgatory_info *pi,
-					Elf_Shdr *section,
-					const Elf_Shdr *relsec,
-					const Elf_Shdr *symtab);
+/* Architectures may override the below functions */
+int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
+				  unsigned long buf_len);
+void *arch_kexec_kernel_image_load(struct kimage *image);
+int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
+				     Elf_Shdr *section,
+				     const Elf_Shdr *relsec,
+				     const Elf_Shdr *symtab);
+int arch_kexec_apply_relocations(struct purgatory_info *pi,
+				 Elf_Shdr *section,
+				 const Elf_Shdr *relsec,
+				 const Elf_Shdr *symtab);
+int arch_kimage_file_post_load_cleanup(struct kimage *image);
+#ifdef CONFIG_KEXEC_SIG
+int arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
+				 unsigned long buf_len);
+#endif
+int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf);
 
 extern int kexec_add_buffer(struct kexec_buf *kbuf);
 int kexec_locate_mem_hole(struct kexec_buf *kbuf);

kernel/kexec_file.c

···
 }
 
 /**
+ * arch_kexec_locate_mem_hole - Find free memory to place the segments.
+ * @kbuf:                       Parameters for the memory search.
+ *
+ * On success, kbuf->mem will have the start address of the memory region found.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int __weak arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
+{
+	return kexec_locate_mem_hole(kbuf);
+}
+
+/**
  * kexec_add_buffer - place a buffer in a kexec segment
  * @kbuf:	Buffer contents and memory parameters.
  *
···
  */
 int kexec_add_buffer(struct kexec_buf *kbuf)
 {
-
 	struct kexec_segment *ksegment;
 	int ret;
 
···
 	kbuf->buf_align = max(kbuf->buf_align, PAGE_SIZE);
 
 	/* Walk the RAM ranges and allocate a suitable range for the buffer */
-	ret = kexec_locate_mem_hole(kbuf);
+	ret = arch_kexec_locate_mem_hole(kbuf);
 	if (ret)
 		return ret;