arm64: kexec_file: Refactor setup_dtb() to consolidate error checking

setup_dtb() is a little difficult to read. This is largely because it
duplicates the FDT -> Linux errno conversion for every intermediate
return value, but also because of silly cosmetic things like naming
and formatting.

Given that this is all brand new, refactor the function to get us off on
the right foot.
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/machine_kexec_file.c

@@ -22,10 +22,10 @@
 #include <asm/byteorder.h>
 
 /* relevant device tree properties */
-#define FDT_PSTR_INITRD_STA	"linux,initrd-start"
-#define FDT_PSTR_INITRD_END	"linux,initrd-end"
-#define FDT_PSTR_BOOTARGS	"bootargs"
-#define FDT_PSTR_KASLR_SEED	"kaslr-seed"
+#define FDT_PROP_INITRD_START	"linux,initrd-start"
+#define FDT_PROP_INITRD_END	"linux,initrd-end"
+#define FDT_PROP_BOOTARGS	"bootargs"
+#define FDT_PROP_KASLR_SEED	"kaslr-seed"
 
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 	&kexec_image_ops,
@@ -44,61 +44,65 @@ static int setup_dtb(struct kimage *image,
 		     unsigned long initrd_load_addr, unsigned long initrd_len,
 		     char *cmdline, void *dtb)
 {
-	int nodeoffset;
-	int ret;
+	int off, ret;
+
+	ret = fdt_path_offset(dtb, "/chosen");
+	if (ret < 0)
+		goto out;
 
-	nodeoffset = fdt_path_offset(dtb, "/chosen");
-	if (nodeoffset < 0)
-		return -EINVAL;
+	off = ret;
 
 	/* add bootargs */
 	if (cmdline) {
-		ret = fdt_setprop_string(dtb, nodeoffset, FDT_PSTR_BOOTARGS,
-							cmdline);
+		ret = fdt_setprop_string(dtb, off, FDT_PROP_BOOTARGS, cmdline);
 		if (ret)
-			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
+			goto out;
 	} else {
-		ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_BOOTARGS);
+		ret = fdt_delprop(dtb, off, FDT_PROP_BOOTARGS);
 		if (ret && (ret != -FDT_ERR_NOTFOUND))
-			return -EINVAL;
+			goto out;
 	}
 
 	/* add initrd-* */
 	if (initrd_load_addr) {
-		ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_INITRD_STA,
-							initrd_load_addr);
+		ret = fdt_setprop_u64(dtb, off, FDT_PROP_INITRD_START,
+				      initrd_load_addr);
 		if (ret)
-			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
+			goto out;
 
-		ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_INITRD_END,
-						initrd_load_addr + initrd_len);
+		ret = fdt_setprop_u64(dtb, off, FDT_PROP_INITRD_END,
+				      initrd_load_addr + initrd_len);
 		if (ret)
-			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
+			goto out;
 	} else {
-		ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_INITRD_STA);
+		ret = fdt_delprop(dtb, off, FDT_PROP_INITRD_START);
 		if (ret && (ret != -FDT_ERR_NOTFOUND))
-			return -EINVAL;
+			goto out;
 
-		ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_INITRD_END);
+		ret = fdt_delprop(dtb, off, FDT_PROP_INITRD_END);
 		if (ret && (ret != -FDT_ERR_NOTFOUND))
-			return -EINVAL;
+			goto out;
 	}
 
 	/* add kaslr-seed */
-	ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_KASLR_SEED);
+	ret = fdt_delprop(dtb, off, FDT_PROP_KASLR_SEED);
 	if (ret && (ret != -FDT_ERR_NOTFOUND))
-		return -EINVAL;
+		goto out;
 
 	if (rng_is_initialized()) {
-		u64 r = get_random_u64();
-		ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_KASLR_SEED, r);
+		u64 seed = get_random_u64();
+		ret = fdt_setprop_u64(dtb, off, FDT_PROP_KASLR_SEED, seed);
 		if (ret)
-			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
+			goto out;
 	} else {
 		pr_notice("RNG is not initialised: omitting \"%s\" property\n",
-				FDT_PSTR_KASLR_SEED);
+				FDT_PROP_KASLR_SEED);
 	}
 
+out:
+	if (ret)
+		return (ret == -FDT_ERR_NOSPACE) ? -ENOMEM : -EINVAL;
+
 	return 0;
 }