Subject: [PATCH v16 11/12] powerpc: Use OF alloc and free for FDT

From: Lakshmi Ramasubramanian <[email-masked]>
Date: Thu, 4 Feb 2021 08:41:34 -0800

of_alloc_and_init_fdt() and of_free_fdt() have been defined in
drivers/of/kexec.c to allocate and free memory for FDT.

Use of_alloc_and_init_fdt() and of_free_fdt() to allocate and
initialize the FDT, and to free the FDT respectively.

powerpc sets the FDT address in image_loader_data field in
"struct kimage" and the memory is freed in
kimage_file_post_load_cleanup().  This cleanup function uses kfree()
to free the memory. But since of_alloc_and_init_fdt() uses kvmalloc()
for allocation, the buffer needs to be freed using kvfree().

Define "fdt" field in "struct kimage_arch" for powerpc to store
the address of FDT, and free the memory in powerpc specific
arch_kimage_file_post_load_cleanup().

Signed-off-by: Lakshmi Ramasubramanian <[email-masked]>
Suggested-by: Rob Herring <[email-masked]>
Suggested-by: Thiago Jung Bauermann <[email-masked]>
---
 arch/powerpc/include/asm/kexec.h  |  2 ++
 arch/powerpc/kexec/elf_64.c       | 26 ++++++++++++++++----------
 arch/powerpc/kexec/file_load_64.c |  3 +++
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 2c0be93d239a..d7d13cac4d31 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -111,6 +111,8 @@ struct kimage_arch {
 	unsigned long elf_headers_mem;
 	unsigned long elf_headers_sz;
 	void *elf_headers;
+
+	void *fdt;
 };
 
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index d0e459bb2f05..51d2d8eb6c1b 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -19,6 +19,7 @@
 #include <linux/kexec.h>
 #include <linux/libfdt.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -32,7 +33,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	unsigned int fdt_size;
 	unsigned long kernel_load_addr;
 	unsigned long initrd_load_addr = 0, fdt_load_addr;
-	void *fdt;
+	void *fdt = NULL;
 	const void *slave_code;
 	struct elfhdr ehdr;
 	char *modified_cmdline = NULL;
@@ -103,18 +104,12 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	}
 
 	fdt_size = fdt_totalsize(initial_boot_params) * 2;
-	fdt = kmalloc(fdt_size, GFP_KERNEL);
+	fdt = of_alloc_and_init_fdt(fdt_size);
 	if (!fdt) {
 		pr_err("Not enough memory for the device tree.\n");
 		ret = -ENOMEM;
 		goto out;
 	}
-	ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
-	if (ret < 0) {
-		pr_err("Error setting up the new device tree.\n");
-		ret = -EINVAL;
-		goto out;
-	}
 
 	ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr,
 				  initrd_len, cmdline);
@@ -131,6 +126,10 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	ret = kexec_add_buffer(&kbuf);
 	if (ret)
 		goto out;
+
+	/* FDT will be freed in arch_kimage_file_post_load_cleanup */
+	image->arch.fdt = fdt;
+
 	fdt_load_addr = kbuf.mem;
 
 	pr_debug("Loaded device tree at 0x%lx\n", fdt_load_addr);
@@ -145,8 +144,15 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	kfree(modified_cmdline);
 	kexec_free_elf_info(&elf_info);
 
-	/* Make kimage_file_post_load_cleanup free the fdt buffer for us. */
-	return ret ? ERR_PTR(ret) : fdt;
+	/*
+	 * Once FDT buffer has been successfully passed to kexec_add_buffer(),
+	 * the FDT buffer address is saved in image->arch.fdt. In that case,
+	 * the memory cannot be freed here in case of any other error.
+	 */
+	if (ret && !image->arch.fdt)
+		of_free_fdt(fdt);
+
+	return ret ? ERR_PTR(ret) : NULL;
 }
 
 const struct kexec_file_ops kexec_elf64_ops = {
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index 3cab318aa3b9..d9d5b5569a6d 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -1113,5 +1113,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	image->arch.elf_headers = NULL;
 	image->arch.elf_headers_sz = 0;
 
+	of_free_fdt(image->arch.fdt);
+	image->arch.fdt = NULL;
+
 	return kexec_image_post_load_cleanup_default(image);
 }
-- 
2.30.0