[RFC PATCH 1/8] ppc/spapr: add PReP boot partition detection

From: Utkarsh Verma <[email protected]>

Add spapr_vof_partition.c which implements basic MBR and GPT partition
table scanning to locate the PReP boot partition during VOF enabled boot.

AI-used-for: code
Signed-off-by: Utkarsh Verma <[email protected]>
---
 hw/ppc/meson.build           |   5 +-
 hw/ppc/spapr_vof_partition.c | 176 +++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr_vof.h   |  14 +++
 3 files changed, 194 insertions(+), 1 deletion(-)
 create mode 100644 hw/ppc/spapr_vof_partition.c
 create mode 100644 include/hw/ppc/spapr_vof.h

diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
index 37aa535db2..68a5d2622f 100644
--- a/hw/ppc/meson.build
+++ b/hw/ppc/meson.build
@@ -93,6 +93,9 @@ ppc_ss.add(when: 'CONFIG_AMIGAONE', if_true: files('amigaone.c'))
 ppc_ss.add(when: 'CONFIG_PEGASOS', if_true: files('pegasos.c'))
 
 ppc_ss.add(when: 'CONFIG_VOF', if_true: files('vof.c'))
-ppc_ss.add(when: ['CONFIG_VOF', 'CONFIG_PSERIES'], if_true: files('spapr_vof.c'))
+ppc_ss.add(when: ['CONFIG_VOF', 'CONFIG_PSERIES'], if_true: files(
+  'spapr_vof.c',
+  'spapr_vof_partition.c',
+))
 
 hw_arch += {'ppc': ppc_ss}
diff --git a/hw/ppc/spapr_vof_partition.c b/hw/ppc/spapr_vof_partition.c
new file mode 100644
index 0000000000..ced2818998
--- /dev/null
+++ b/hw/ppc/spapr_vof_partition.c
@@ -0,0 +1,176 @@
+/*
+ * QEMU PowerPC sPAPR VOF Partition Table Support.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This implements partition table detection for VOF boot,
+ * supporting MBR and GPT partition tables with focus on PReP boot partition.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/bswap.h"
+#include "qemu/error-report.h"
+#include "system/block-backend-io.h"
+#include "hw/ppc/spapr_vof.h"
+
+#define SECTOR_SIZE              512
+#define MBR_PARTITION_ENTRY_SIZE 16
+#define MBR_PARTITION_TABLE_OFFSET 446
+#define MBR_NUM_PARTITIONS       4
+
+#define PARTITION_TYPE_PREP      0x41  /* PReP Boot partition */
+#define PARTITION_TYPE_GPT       0xEE
+
+#define GPT_SIGNATURE            "EFI PART"
+#define GPT_SIGNATURE_SIZE       8
+
+/* PReP Boot: 9E1A2D38-C612-4316-AA26-8B49521E5A8B */
+static const uint8_t GUID_PREP_BOOT[16] = {
+    0x38, 0x2D, 0x1A, 0x9E, 0x12, 0xC6, 0x16, 0x43,
+    0xAA, 0x26, 0x8B, 0x49, 0x52, 0x1E, 0x5A, 0x8B
+};
+
+typedef struct MBRPartitionEntry {
+    uint8_t  boot_flag;
+    uint8_t  start_chs[3];
+    uint8_t  type;
+    uint8_t  end_chs[3];
+    uint32_t start_lba;
+    uint32_t num_sectors;
+} QEMU_PACKED MBRPartitionEntry;
+
+typedef struct GPTHeader {
+    char     signature[8];
+    uint32_t revision;
+    uint32_t header_size;
+    uint32_t header_crc32;
+    uint32_t reserved;
+    uint64_t current_lba;
+    uint64_t backup_lba;
+    uint64_t first_usable_lba;
+    uint64_t last_usable_lba;
+    uint8_t  disk_guid[16];
+    uint64_t partition_entries_lba;
+    uint32_t num_partition_entries;
+    uint32_t partition_entry_size;
+    uint32_t partition_array_crc32;
+} QEMU_PACKED GPTHeader;
+
+typedef struct GPTPartitionEntry {
+    uint8_t  type_guid[16];
+    uint8_t  partition_guid[16];
+    uint64_t first_lba;
+    uint64_t last_lba;
+    uint64_t attributes;
+    uint16_t name[36];
+} QEMU_PACKED GPTPartitionEntry;
+
+static bool find_prep_partition_gpt(BlockBackend *blk,
+                                    uint64_t *offset, uint64_t *size)
+{
+    uint8_t lba1[SECTOR_SIZE];
+    GPTHeader *header;
+    uint64_t entries_lba;
+    uint32_t num_entries;
+    uint32_t entry_size;
+    uint64_t current_entry_offset;
+    uint8_t *buf;
+    GPTPartitionEntry *current_entry;
+    uint32_t i;
+    int ret;
+
+    ret = blk_pread(blk, SECTOR_SIZE, SECTOR_SIZE, lba1, 0);
+    if (ret < 0) {
+        warn_report("GPT: failed to read LBA1 (ret=%d)", ret);
+        return false;
+    }
+
+    header = (GPTHeader *)lba1;
+
+    if (memcmp(header->signature, GPT_SIGNATURE, GPT_SIGNATURE_SIZE) != 0) {
+        return false;
+    }
+
+    entries_lba = le64_to_cpu(header->partition_entries_lba);
+    num_entries = le32_to_cpu(header->num_partition_entries);
+    entry_size = le32_to_cpu(header->partition_entry_size);
+
+    if (num_entries > 128) {
+        num_entries = 128;
+    }
+
+    if (entry_size < 128) {
+        return false;
+    }
+
+    buf = g_malloc(entry_size);
+    for (i = 0; i < num_entries; i++) {
+        current_entry_offset = (entries_lba * SECTOR_SIZE) +
+                               ((uint64_t)i * entry_size);
+
+        ret = blk_pread(blk, current_entry_offset, entry_size, buf, 0);
+        if (ret < 0) {
+            warn_report("GPT: failed to read partition entry %u "
+                        "(ret=%d)", i, ret);
+            g_free(buf);
+            return false;
+        }
+
+        current_entry = (GPTPartitionEntry *)buf;
+        if (memcmp(current_entry->type_guid, GUID_PREP_BOOT,
+                   sizeof(GUID_PREP_BOOT)) == 0) {
+            *offset = le64_to_cpu(current_entry->first_lba) * SECTOR_SIZE;
+            *size = (le64_to_cpu(current_entry->last_lba) -
+                     le64_to_cpu(current_entry->first_lba) + 1) * SECTOR_SIZE;
+            g_free(buf);
+            return true;
+        }
+    }
+    g_free(buf);
+    return false;
+}
+
+static bool find_prep_partition_mbr(BlockBackend *blk,
+                                    uint64_t *offset, uint64_t *size)
+{
+    uint8_t mbr[SECTOR_SIZE];
+    MBRPartitionEntry *entry;
+    int ret;
+    int i;
+
+    ret = blk_pread(blk, 0, SECTOR_SIZE, mbr, 0);
+    if (ret < 0) {
+        warn_report("MBR: failed to read MBR sector (ret=%d)", ret);
+        return false;
+    }
+
+    /* MBR boot signature: byte 510 = 0x55, byte 511 = 0xAA */
+    if (mbr[510] != 0x55 || mbr[511] != 0xAA) {
+        return false;
+    }
+
+    for (i = 0; i < MBR_NUM_PARTITIONS; i++) {
+        entry = (MBRPartitionEntry *)&mbr[MBR_PARTITION_TABLE_OFFSET +
+                                          i * MBR_PARTITION_ENTRY_SIZE];
+
+        if (entry->type == PARTITION_TYPE_GPT) {
+            return find_prep_partition_gpt(blk, offset, size);
+        }
+
+        if (entry->type == PARTITION_TYPE_PREP) {
+            *offset = (uint64_t)le32_to_cpu(entry->start_lba) * SECTOR_SIZE;
+            *size = (uint64_t)le32_to_cpu(entry->num_sectors) * SECTOR_SIZE;
+            return true;
+        }
+    }
+    return false;
+}
+
+bool spapr_vof_find_prep_partition(BlockBackend *blk,
+                                   uint64_t *offset, uint64_t *size)
+{
+    if (!blk) {
+        return false;
+    }
+    return find_prep_partition_mbr(blk, offset, size);
+}
diff --git a/include/hw/ppc/spapr_vof.h b/include/hw/ppc/spapr_vof.h
new file mode 100644
index 0000000000..08787d2aeb
--- /dev/null
+++ b/include/hw/ppc/spapr_vof.h
@@ -0,0 +1,14 @@
+/*
+ * QEMU PowerPC sPAPR VOF Support
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef HW_SPAPR_VOF_H
+#define HW_SPAPR_VOF_H
+
+typedef struct BlockBackend BlockBackend;
+
+bool spapr_vof_find_prep_partition(BlockBackend *blk,
+                                   uint64_t *offset, uint64_t *size);
+
+#endif /* HW_SPAPR_VOF_H */
-- 
2.54.0