optionrom: add new PVH option rom

The new pvh.bin option rom can be used with SeaBIOS to boot
uncompressed kernel using the x86/HVM direct boot ABI.

pvh.S contains the entry point of the option rom. It runs
in real mode, loads the e820 table querying the BIOS, and
then it switches to 32bit protected mode and jumps to the
pvh_load_kernel() written in pvh_main.c.
pvh_load_kernel() loads the cmdline and kernel entry_point
using fw_cfg, then it looks for RSDP, fills the
hvm_start_info required by x86/HVM ABI, and finally jumps
to the kernel entry_point.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/pc-bios/optionrom/pvh_main.c b/pc-bios/optionrom/pvh_main.c
new file mode 100644
index 0000000000..1dcc5c9256
--- /dev/null
+++ b/pc-bios/optionrom/pvh_main.c
@@ -0,0 +1,116 @@
+/*
+ * PVH Option ROM for fw_cfg DMA
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (c) 2019 Red Hat Inc.
+ *   Authors:
+ *     Stefano Garzarella <sgarzare@redhat.com>
+ */
+
+asm (".code32"); /* this code will be executed in protected mode */
+
+#include <stddef.h>
+#include <stdint.h>
+#include "optrom.h"
+#include "optrom_fw_cfg.h"
+#include "../../include/hw/xen/start_info.h"
+
+#define RSDP_SIGNATURE          0x2052545020445352LL /* "RSD PTR " */
+#define RSDP_AREA_ADDR          0x000E0000
+#define RSDP_AREA_SIZE          2048
+#define EBDA_BASE_ADDR          0x0000040E
+#define EBDA_SIZE               1024
+
+#define E820_MAXENTRIES         128
+#define CMDLINE_BUFSIZE         4096
+
+/* e820 table filled in pvh.S using int 0x15 */
+struct pvh_e820_table {
+    uint32_t entries;
+    uint32_t reserved;
+    struct hvm_memmap_table_entry table[E820_MAXENTRIES];
+};
+
+struct pvh_e820_table pvh_e820 asm("pvh_e820") __attribute__ ((aligned));
+
+static struct hvm_start_info start_info;
+static uint8_t cmdline_buffer[CMDLINE_BUFSIZE];
+
+
+/* Search RSDP signature. */
+static uintptr_t search_rsdp(uint32_t start_addr, uint32_t end_addr)
+{
+    uint64_t *rsdp_p;
+
+    /* RSDP signature is always on a 16 byte boundary */
+    for (rsdp_p = (uint64_t *)start_addr; rsdp_p < (uint64_t *)end_addr;
+         rsdp_p += 2) {
+        if (*rsdp_p == RSDP_SIGNATURE) {
+            return (uintptr_t)rsdp_p;
+        }
+    }
+
+    return 0;
+}
+
+/* Force the asm name without leading underscore, even on Win32. */
+extern void pvh_load_kernel(void) asm("pvh_load_kernel");
+
+void pvh_load_kernel(void)
+{
+    void *cmdline_addr = &cmdline_buffer;
+    void *kernel_entry;
+    uint32_t cmdline_size, fw_cfg_version = bios_cfg_version();
+
+    start_info.magic = XEN_HVM_START_MAGIC_VALUE;
+    start_info.version = 1;
+
+    /*
+     * pvh_e820 is filled in the pvh.S before to switch in protected mode,
+     * because we can use int 0x15 only in real mode.
+     */
+    start_info.memmap_entries = pvh_e820.entries;
+    start_info.memmap_paddr = (uintptr_t)pvh_e820.table;
+
+    /*
+     * Search RSDP in the main BIOS area below 1 MB.
+     * SeaBIOS store the RSDP in this area, so we try it first.
+     */
+    start_info.rsdp_paddr = search_rsdp(RSDP_AREA_ADDR,
+                                        RSDP_AREA_ADDR + RSDP_AREA_SIZE);
+
+    /* Search RSDP in the EBDA if it is not found */
+    if (!start_info.rsdp_paddr) {
+        /*
+         * Th EBDA address is stored at EBDA_BASE_ADDR. It contains 2 bytes
+         * segment pointer to EBDA, so we must convert it to a linear address.
+         */
+        uint32_t ebda_paddr = ((uint32_t)*((uint16_t *)EBDA_BASE_ADDR)) << 4;
+        if (ebda_paddr > 0x400) {
+            uint32_t *ebda = (uint32_t *)ebda_paddr;
+
+            start_info.rsdp_paddr = search_rsdp(*ebda, *ebda + EBDA_SIZE);
+        }
+    }
+
+    bios_cfg_read_entry(&cmdline_size, FW_CFG_CMDLINE_SIZE, 4, fw_cfg_version);
+    bios_cfg_read_entry(cmdline_addr, FW_CFG_CMDLINE_DATA, cmdline_size,
+                        fw_cfg_version);
+    start_info.cmdline_paddr = (uintptr_t)cmdline_addr;
+
+    bios_cfg_read_entry(&kernel_entry, FW_CFG_KERNEL_ENTRY, 4, fw_cfg_version);
+
+    asm volatile("jmp *%1" : : "b"(&start_info), "c"(kernel_entry));
+}