[coreboot-gerrit] Change in coreboot[master]: riscv: add trampoline in MBR block to support boot mode 1

[Philipp Hug (Code Review)]

Philipp Hug has uploaded this change for review. ( https://review.coreboot.org/27397

Change subject: riscv: add trampoline in MBR block to support boot mode 1
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riscv: add trampoline in MBR block to support boot mode 1

Add "J pc + 0x1000" at the beginning of the MBR to jump to bootlock.
Changed first usable lba to 4 (0x1000) as prevent stack alignment
issues.

Change-Id: I16e762d9f027346b124412f1f7ee6ff37f431d86
---
M util/riscv/sifive-gpt.py
1 file changed, 9 insertions(+), 7 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/97/27397/1

diff --git a/util/riscv/sifive-gpt.py b/util/riscv/sifive-gpt.py
index cb77302..2619a21 100755
--- a/util/riscv/sifive-gpt.py
+++ b/util/riscv/sifive-gpt.py
@@ -25,6 +25,12 @@
 # Size of the bootcode part of the MBR
 MBR_BOOTCODE_SIZE = 0x1be

+# MBR trampoline to bootblock
+MBR_BOOTCODE = bytes([
+    # j pc + 0x1000
+    0x6f, 0x10, 0x00, 0x00,
+])
+
 # A protecive MBR, without the bootcode part
 PROTECTIVE_MBR_FOOTER = bytes([
     0x00, 0x00, 0x02, 0x00, 0xee, 0xff, 0xff, 0xff,
@@ -43,7 +49,7 @@
 # [1]: https://en.wikipedia.org/wiki/GUID_Partition_Table#PROTECTIVE-MBR
 class ProtectiveMBR:
     def __init__(self):
-        self.bootcode = bytes(MBR_BOOTCODE_SIZE)
+        self.bootcode = MBR_BOOTCODE + bytes(MBR_BOOTCODE_SIZE - len(MBR_BOOTCODE))

def generate(self, stream):
         assert len(self.bootcode) == MBR_BOOTCODE_SIZE
@@ -71,7 +77,7 @@
     def __init__(self):
         self.current_lba = 1
         self.backup_lba = 1
-        self.first_usable_lba = 2
+        self.first_usable_lba = 8       # hard-coded to match jump
         self.last_usable_lba = 0xff     # dummy value
         self.uniq = DUMMY_GUID_DISK_UNIQUE
         self.part_entries_lba = 2
@@ -126,7 +132,7 @@
     def __init__(self):
         self.mbr = ProtectiveMBR()
         self.header = GPTHeader()
-        self.partitions = [ GPTPartition() for i in range(8) ]
+        self.partitions = [ GPTPartition() for i in range(24) ]
         self.bootblock = b''

@@ -137,10 +143,6 @@
         bootblock_size = (len(self.bootblock) + BLOCK_SIZE - 1) & ~BLOCK_MASK
         self.bootblock = self.bootblock.ljust(bootblock_size)

-        # Propagate the number of partition entries
-        self.header.part_entries_number = len(self.partitions)
-        self.header.first_usable_lba = 2 + self.header.part_entries_number // 4
-
         # Create a partition entry for the bootblock
         self.partitions[0].type = GUID_TYPE_FSBL
         self.partitions[0].uniq = DUMMY_GUID_PART_UNIQUE