Subject: [PATCH 2/8] kexec_file: Generalize kexec_add_buffer.

From: Thiago Jung Bauermann <[email-masked]>
Date: Sun, 12 Jun 2016 00:10:16 -0300

Allow architectures to specify different memory walking functions for
kexec_add_buffer. Intel uses iomem to track reserved memory ranges,
but PowerPC uses the memblock subsystem.

Also, factor kexec_locate_mem_hole out of kexec_add_buffer. It will be
used by the PowerPC kexec_file_load implementation to find free memory
for the purgatory stack.

Cc: Eric Biederman <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
---
 include/linux/kexec.h | 10 ++++++
 kernel/kexec_file.c   | 96 +++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 81 insertions(+), 25 deletions(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index e8acb2b43dd9..920e2cbe5bdd 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -210,6 +210,10 @@ extern asmlinkage long sys_kexec_load(unsigned long entry,
 					struct kexec_segment __user *segments,
 					unsigned long flags);
 extern int kernel_kexec(void);
+int kexec_locate_mem_hole(struct kimage *image, unsigned long size,
+			  unsigned long align, unsigned long start,
+			  unsigned long end, bool top_down,
+			  unsigned long *addr);
 extern int kexec_add_buffer(struct kimage *image, char *buffer,
 			    unsigned long bufsz, unsigned long memsz,
 			    unsigned long buf_align, unsigned long buf_min,
@@ -315,6 +319,12 @@ int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
 					Elf_Shdr *sechdrs, unsigned int relsec);
 int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 					unsigned int relsec);
+int __weak arch_walk_iomem(unsigned long desc, unsigned long start,
+			   unsigned long end, bool top_down, void *data,
+			   int (*func)(u64, u64, void *));
+int __weak arch_walk_system_ram(unsigned long start, unsigned long end,
+				bool top_down, void *data,
+				int (*func)(u64, u64, void *));
 void arch_kexec_protect_crashkres(void);
 void arch_kexec_unprotect_crashkres(void);
 
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b6eec7527e9f..300f71cb4f72 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -428,6 +428,68 @@ static int locate_mem_hole_callback(u64 start, u64 end, void *arg)
 	return locate_mem_hole_bottom_up(start, end, kbuf);
 }
 
+int __weak arch_walk_iomem(unsigned long desc, unsigned long start,
+			   unsigned long end, bool top_down, void *data,
+			   int (*func)(u64, u64, void *))
+{
+	return walk_iomem_res_desc(desc,
+				   IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
+				   start, end, data, func);
+}
+
+int __weak arch_walk_system_ram(unsigned long start, unsigned long end,
+				bool top_down, void *data,
+				int (*func)(u64, u64, void *))
+{
+	return walk_system_ram_res(start, end, data, func);
+}
+
+/**
+ * kexec_locate_mem_hole - find free memory to load segment or use in purgatory
+ * @image:	kexec image being updated.
+ * @size:	Memory size.
+ * @align:	Minimum alignment needed.
+ * @start:	Minimum starting address.
+ * @end:	Maximum end address.
+ * @top_down	Find the highest free memory region?
+ * @addr	On success, will have start address of the memory region found.
+ *
+ * Return: 0 on success, negative erro on failure.
+ */
+int kexec_locate_mem_hole(struct kimage *image, unsigned long size,
+			  unsigned long align, unsigned long start,
+			  unsigned long end, bool top_down, unsigned long *addr)
+{
+	int ret;
+	struct kexec_buf buf;
+
+	memset(&buf, 0, sizeof(struct kexec_buf));
+	buf.image = image;
+
+	buf.memsz = size;
+	buf.buf_align = align;
+	buf.buf_min = start;
+	buf.buf_max = end;
+	buf.top_down = top_down;
+
+	/* Walk the RAM ranges and allocate a suitable range for the buffer */
+	if (image->type == KEXEC_TYPE_CRASH)
+		ret = arch_walk_iomem(crashk_res.desc, crashk_res.start,
+				      crashk_res.end, top_down, &buf,
+				      locate_mem_hole_callback);
+	else
+		ret = arch_walk_system_ram(0, -1, top_down, &buf,
+					   locate_mem_hole_callback);
+	if (ret != 1) {
+		/* A suitable memory range could not be found for buffer */
+		return -EADDRNOTAVAIL;
+	}
+
+	*addr = buf.mem;
+
+	return 0;
+}
+
 /*
  * Helper function for placing a buffer in a kexec segment. This assumes
  * that kexec_mutex is held.
@@ -439,8 +501,8 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
 {
 
 	struct kexec_segment *ksegment;
-	struct kexec_buf buf, *kbuf;
 	int ret;
+	unsigned long addr, align, size;
 
 	/* Currently adding segment this way is allowed only in file mode */
 	if (!image->file_mode)
@@ -461,36 +523,20 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
 		return -EINVAL;
 	}
 
-	memset(&buf, 0, sizeof(struct kexec_buf));
-	kbuf = &buf;
-	kbuf->image = image;
-
-	kbuf->memsz = ALIGN(memsz, PAGE_SIZE);
-	kbuf->buf_align = max(buf_align, PAGE_SIZE);
-	kbuf->buf_min = buf_min;
-	kbuf->buf_max = buf_max;
-	kbuf->top_down = top_down;
+	size = ALIGN(memsz, PAGE_SIZE);
+	align = max(buf_align, PAGE_SIZE);
 
-	/* Walk the RAM ranges and allocate a suitable range for the buffer */
-	if (image->type == KEXEC_TYPE_CRASH)
-		ret = walk_iomem_res_desc(crashk_res.desc,
-				IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
-				crashk_res.start, crashk_res.end, kbuf,
-				locate_mem_hole_callback);
-	else
-		ret = walk_system_ram_res(0, -1, kbuf,
-					  locate_mem_hole_callback);
-	if (ret != 1) {
-		/* A suitable memory range could not be found for buffer */
-		return -EADDRNOTAVAIL;
-	}
+	ret = kexec_locate_mem_hole(image, size, align, buf_min, buf_max,
+				    top_down, &addr);
+	if (ret)
+		return ret;
 
 	/* Found a suitable memory range */
 	ksegment = &image->segment[image->nr_segments];
 	ksegment->kbuf = buffer;
 	ksegment->bufsz = bufsz;
-	ksegment->mem = kbuf->mem;
-	ksegment->memsz = kbuf->memsz;
+	ksegment->mem = addr;
+	ksegment->memsz = size;
 	image->nr_segments++;
 	*load_addr = ksegment->mem;
 	return 0;
-- 
1.9.1