Re: [v4 PATCH 2/3] RISC-V: Update image header

From: Heinrich Schuchardt
Date: Thu Oct 06 2022 - 19:51:41 EST




On 10/7/22 01:00, Atish Patra wrote:
Update the RISC-V Linux kernel image headers as per the current header.

Reference:
<Linux kernel source>/Documentation/riscv/boot-image-header.rst

474efecb65dc: ("riscv: modify the Image header to improve compatibility with the ARM64 header")

Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
---
include/grub/riscv32/linux.h | 15 ++++++++-------
include/grub/riscv64/linux.h | 21 +++++++++++++--------
2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/include/grub/riscv32/linux.h b/include/grub/riscv32/linux.h
index 512b777c8a41..de0dbdcd1be5 100644
--- a/include/grub/riscv32/linux.h
+++ b/include/grub/riscv32/linux.h
@@ -19,20 +19,21 @@
#ifndef GRUB_RISCV32_LINUX_HEADER
#define GRUB_RISCV32_LINUX_HEADER 1
-#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x52534356 /* 'RSCV' */
+#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x05435352 /* 'RSC\0x5' */

Thanks for following up on this series.

Considering 69edb312056 ("loader/arm64/linux: Remove magic number header field check") why should this constant exist in GRUB at all?

In a follow up patch we could remove it together with GRUB_LINUX_ARM_MAGIC_SIGNATURE, GRUB_LINUX_ARMXX_MAGIC_SIGNATURE, and GRUB_LINUX_ARMXX_MAGIC_SIGNATURE.

-/* From linux/Documentation/riscv/booting.txt */
+/* From linux/Documentation/riscv/boot-image-header.rst */
struct linux_riscv_kernel_header
{
grub_uint32_t code0; /* Executable code */
grub_uint32_t code1; /* Executable code */
- grub_uint64_t text_offset; /* Image load offset */
- grub_uint64_t res0; /* reserved */
- grub_uint64_t res1; /* reserved */
+ grub_uint64_t text_offset; /* Image load offset, little endian */
+ grub_uint64_t image_size; /* Effective Image size, little endian */
+ grub_uint64_t flags; /* kernel flags, little endian */
+ grub_uint32_t version; /* Version of this header */
+ grub_uint32_t res1; /* reserved */
grub_uint64_t res2; /* reserved */
grub_uint64_t res3; /* reserved */

According to tag next-20221006 of Documentation/riscv/boot-image-header.rst and of arch/riscv/include/asm/image.h this field is called 'magic' and filled it with the string 'RISCV\0\0\0'.

- grub_uint64_t res4; /* reserved */
- grub_uint32_t magic; /* Magic number, little endian, "RSCV" */
+ grub_uint32_t magic; /* Magic number, little endian, "RSC\x05" */

The Linux kernel documentation calls this field magic2.

Of course this is functionally irrelevant as we don't care about the content of both fields.

grub_uint32_t hdr_offset; /* Offset of PE/COFF header */
};
diff --git a/include/grub/riscv64/linux.h b/include/grub/riscv64/linux.h
index 3630c30fbf1a..ea77f8718222 100644
--- a/include/grub/riscv64/linux.h
+++ b/include/grub/riscv64/linux.h
@@ -19,23 +19,28 @@
#ifndef GRUB_RISCV64_LINUX_HEADER
#define GRUB_RISCV64_LINUX_HEADER 1
-#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x52534356 /* 'RSCV' */
+#include <grub/efi/pe32.h>
+
+#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x05435352 /* 'RSC\0x5' */

to be removed in future

Best regards

Heinrich

#define GRUB_EFI_PE_MAGIC 0x5A4D
-/* From linux/Documentation/riscv/booting.txt */
+/* From linux/Documentation/riscv/boot-image-header.rst */
struct linux_riscv_kernel_header
{
grub_uint32_t code0; /* Executable code */
grub_uint32_t code1; /* Executable code */
- grub_uint64_t text_offset; /* Image load offset */
- grub_uint64_t res0; /* reserved */
- grub_uint64_t res1; /* reserved */
+ grub_uint64_t text_offset; /* Image load offset, little endian */
+ grub_uint64_t image_size; /* Effective Image size, little endian */
+ grub_uint64_t flags; /* kernel flags, little endian */
+ grub_uint32_t version; /* Version of this header */
+ grub_uint32_t res1; /* reserved */
grub_uint64_t res2; /* reserved */
- grub_uint64_t res3; /* reserved */
- grub_uint64_t res4; /* reserved */
- grub_uint32_t magic; /* Magic number, little endian, "RSCV" */
+ grub_uint64_t magic; /* magic (RISC-V specifc, deprecated)*/
+ grub_uint32_t magic2; /* Magic number 2 (to match the ARM64 'magic' field pos) */
grub_uint32_t hdr_offset; /* Offset of PE/COFF header */
+
+ struct grub_coff_image_header coff_image_header;
};
#define linux_arch_kernel_header linux_riscv_kernel_header