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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2015-07-29 12:30:39 +0100
committerWill Deacon <will.deacon@arm.com>2015-07-29 18:32:10 +0100
commit6c020ea8dc3a8adee81b6f141428a7a75249706e (patch)
treebe392025b6ec76a92a74415ac0238af54de4bce2 /Documentation/arm64
parent484c96dbb26965d712a808ab9e8b00090455bdf6 (diff)
arm64/Documentation: clarify wording regarding memory below the Image
Clarify that the memory below the start of the image but inside the region covered by the linear mapping has no special significance to the kernel, and may be used by the firmware provided that it is marked as reserved. Also, fix up some whitespace errors. Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'Documentation/arm64')
-rw-r--r--Documentation/arm64/booting.txt11
1 files changed, 7 insertions, 4 deletions
diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
index 1690350f16e7..7d9d3c2286b2 100644
--- a/Documentation/arm64/booting.txt
+++ b/Documentation/arm64/booting.txt
@@ -81,7 +81,7 @@ The decompressed kernel image contains a 64-byte header as follows:
u64 res3 = 0; /* reserved */
u64 res4 = 0; /* reserved */
u32 magic = 0x644d5241; /* Magic number, little endian, "ARM\x64" */
- u32 res5; /* reserved (used for PE COFF offset) */
+ u32 res5; /* reserved (used for PE COFF offset) */
Header notes:
@@ -103,7 +103,7 @@ Header notes:
- The flags field (introduced in v3.17) is a little-endian 64-bit field
composed as follows:
- Bit 0: Kernel endianness. 1 if BE, 0 if LE.
+ Bit 0: Kernel endianness. 1 if BE, 0 if LE.
Bits 1-63: Reserved.
- When image_size is zero, a bootloader should attempt to keep as much
@@ -115,11 +115,14 @@ The Image must be placed text_offset bytes from a 2MB aligned base
address near the start of usable system RAM and called there. Memory
below that base address is currently unusable by Linux, and therefore it
is strongly recommended that this location is the start of system RAM.
+The region between the 2 MB aligned base address and the start of the
+image has no special significance to the kernel, and may be used for
+other purposes.
At least image_size bytes from the start of the image must be free for
use by the kernel.
-Any memory described to the kernel (even that below the 2MB aligned base
-address) which is not marked as reserved from the kernel e.g. with a
+Any memory described to the kernel (even that below the start of the
+image) which is not marked as reserved from the kernel (e.g., with a
memreserve region in the device tree) will be considered as available to
the kernel.