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authorPaul Walmsley <paul.walmsley@sifive.com>2019-09-13 18:35:50 -0700
committerPaul Walmsley <paul.walmsley@sifive.com>2019-09-13 19:03:52 -0700
commit474efecb65dceb15f793b6e2f2b226e952f0f8e9 (patch)
parentf74c2bb98776e2de508f4d607cd519873065118e (diff)
riscv: modify the Image header to improve compatibility with the ARM64 header
Part of the intention during the definition of the RISC-V kernel image header was to lay the groundwork for a future merge with the ARM64 image header. One error during my original review was not noticing that the RISC-V header's "magic" field was at a different size and position than the ARM64's "magic" field. If the existing ARM64 Image header parsing code were to attempt to parse an existing RISC-V kernel image header format, it would see a magic number 0. This is undesirable, since it's our intention to align as closely as possible with the ARM64 header format. Another problem was that the original "res3" field was not being initialized correctly to zero. Address these issues by creating a 32-bit "magic2" field in the RISC-V header which matches the ARM64 "magic" field. RISC-V binaries will store "RSC\x05" in this field. The intention is that the use of the existing 64-bit "magic" field in the RISC-V header will be deprecated over time. Increment the minor version number of the file format to indicate this change, and update the documentation accordingly. Fix the assembler directives in head.S to ensure that reserved fields are properly zero-initialized. Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com> Reported-by: Palmer Dabbelt <palmer@sifive.com> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> Cc: Atish Patra <atish.patra@wdc.com> Cc: Karsten Merker <merker@debian.org> Link: https://lore.kernel.org/linux-riscv/194c2f10c9806720623430dbf0cc59a965e50448.camel@wdc.com/T/#u Link: https://lore.kernel.org/linux-riscv/mhng-755b14c4-8f35-4079-a7ff-e421fd1b02bc@palmer-si-x1e/T/#t
3 files changed, 15 insertions, 14 deletions
diff --git a/Documentation/riscv/boot-image-header.txt b/Documentation/riscv/boot-image-header.txt
index 1b73fea23b39..14b1492f689b 100644
--- a/Documentation/riscv/boot-image-header.txt
+++ b/Documentation/riscv/boot-image-header.txt
@@ -18,7 +18,7 @@ The following 64-byte header is present in decompressed Linux kernel image.
u32 res1 = 0; /* Reserved */
u64 res2 = 0; /* Reserved */
u64 magic = 0x5643534952; /* Magic number, little endian, "RISCV" */
- u32 res3; /* Reserved for additional RISC-V specific header */
+ u32 magic2 = 0x56534905; /* Magic number 2, little endian, "RSC\x05" */
u32 res4; /* Reserved for PE COFF offset */
This header format is compliant with PE/COFF header and largely inspired from
@@ -37,13 +37,14 @@ Notes:
Bits 16:31 - Major version
This preserves compatibility across newer and older version of the header.
- The current version is defined as 0.1.
+ The current version is defined as 0.2.
-- res3 is reserved for offset to any other additional fields. This makes the
- header extendible in future. One example would be to accommodate ISA
- extension for RISC-V in future. For current version, it is set to be zero.
+- The "magic" field is deprecated as of version 0.2. In a future
+ release, it may be removed. This originally should have matched up
+ with the ARM64 header "magic" field, but unfortunately does not.
+ The "magic2" field replaces it, matching up with the ARM64 header.
-- In current header, the flag field has only one field.
+- In current header, the flags field has only one field.
Bit 0: Kernel endianness. 1 if BE, 0 if LE.
- Image size is mandatory for boot loader to load kernel image. Booting will
diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h
index ef28e106f247..344db5244547 100644
--- a/arch/riscv/include/asm/image.h
+++ b/arch/riscv/include/asm/image.h
@@ -3,7 +3,8 @@
#ifndef __ASM_IMAGE_H
#define __ASM_IMAGE_H
+#define RISCV_IMAGE_MAGIC "RISCV\0\0\0"
+#define RISCV_IMAGE_MAGIC2 "RSC\x05"
@@ -23,7 +24,7 @@
#define __HEAD_FLAGS (__HEAD_FLAG(BE))
@@ -39,9 +40,8 @@
* @version: version
* @res1: reserved
* @res2: reserved
- * @magic: Magic number
- * @res3: reserved (will be used for additional RISC-V specific
- * header)
+ * @magic: Magic number (RISC-V specific; deprecated)
+ * @magic2: Magic number 2 (to match the ARM64 'magic' field pos)
* @res4: reserved (will be used for PE COFF offset)
* The intention is for this header format to be shared between multiple
@@ -58,7 +58,7 @@ struct riscv_image_header {
u32 res1;
u64 res2;
u64 magic;
- u32 res3;
+ u32 magic2;
u32 res4;
#endif /* __ASSEMBLY__ */
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 0f1ba17e476f..52eec0c1bf30 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -39,9 +39,9 @@ ENTRY(_start)
.word 0
.dword 0
- .word 0
.balign 4
.word 0
.global _start_kernel