[U-Boot] [PATCH v2] arm64: booti: allow to place kernel image anywhere in physical memory

[Masahiro Yamada]

At first, the ARM64 Linux booting requirement recommended that the
kernel image be placed text_offset bytes from 2MB aligned base near
the start of usable system RAM because memory below that base address
was unusable at that time.

This requirement was relaxed by Linux commit a7f8de168ace ("arm64:
allow kernel Image to be loaded anywhere in physical memory").
Since then, the bit 3 of the flags field indicates the tolerance
of the kernel physical placement.  If this bit is set, the 2MB
aligned base may be anywhere in physical memory.  For details, see
Documentation/arm64/booting.txt of Linux.

The booti command should be also relaxed.  If the bit 3 is set,
images->ep is respected, and the image is placed at the nearest
bootable location.  Otherwise, it is relocated to the start of the
system RAM to keep the original behavior.

Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>
---

Changes in v2:
  - Use le64_to_cpu() for correct endian-ness
  - Check the bit 3

 cmd/booti.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/cmd/booti.c b/cmd/booti.c
index bff87a8..8f3507d 100644
--- a/cmd/booti.c
+++ b/cmd/booti.c
@@ -11,6 +11,8 @@
 #include <image.h>
 #include <lmb.h>
 #include <mapmem.h>
+#include <linux/kernel.h>
+#include <linux/sizes.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -20,7 +22,7 @@ struct Image_header {
 	uint32_t	code1;		/* Executable code */
 	uint64_t	text_offset;	/* Image load offset, LE */
 	uint64_t	image_size;	/* Effective Image size, LE */
-	uint64_t	res1;		/* reserved */
+	uint64_t	flags;		/* Kernel flags, LE */
 	uint64_t	res2;		/* reserved */
 	uint64_t	res3;		/* reserved */
 	uint64_t	res4;		/* reserved */
@@ -51,10 +53,18 @@ static int booti_setup(bootm_headers_t *images)
 	}
 
 	/*
-	 * If we are not at the correct run-time location, set the new
-	 * correct location and then move the image there.
+	 * If bit 3 of the flags field is set, the 2MB aligned base of the
+	 * kernel image can be anywhere in physical memory, so respect
+	 * images->ep.  Otherwise, relocate the image to the base of RAM
+	 * since memory below it is not accessible via the linear mapping.
 	 */
-	dst = gd->bd->bi_dram[0].start + le64_to_cpu(ih->text_offset);
+	if (le64_to_cpu(ih->flags) & BIT(3))
+		dst = images->ep - le64_to_cpu(ih->text_offset);
+	else
+		dst = gd->bd->bi_dram[0].start;
+
+	dst = ALIGN(dst, SZ_2M);
+	dst += le64_to_cpu(ih->text_offset);
 
 	unmap_sysmem(ih);
 
-- 
2.7.4