EDD probing code for the new x86 setup code

Probe EDD and MBR signatures, in order to make it easier to map
physical hard drives to BIOS drives.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 196 insertions, 0 deletions

diff --git a/arch/i386/boot/edd.c b/arch/i386/boot/edd.c
new file mode 100644
index 000000000000..25a282494f4c
--- /dev/null
+++ b/arch/i386/boot/edd.c
@@ -0,0 +1,196 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/edd.c
+ *
+ * Get EDD BIOS disk information
+ */
+
+#include "boot.h"
+#include <linux/edd.h>
+
+#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
+
+struct edd_dapa {
+        u8      pkt_size;
+        u8      rsvd;
+        u16     sector_cnt;
+        u16     buf_off, buf_seg;
+        u64     lba;
+        u64     buf_lin_addr;
+};
+
+/*
+ * Read the MBR (first sector) from a specific device.
+ */
+static int read_mbr(u8 devno, void *buf)
+{
+        struct edd_dapa dapa;
+        u16 ax, bx, cx, dx, si;
+
+        memset(&dapa, 0, sizeof dapa);
+        dapa.pkt_size = sizeof(dapa);
+        dapa.sector_cnt = 1;
+        dapa.buf_off = (size_t)buf;
+        dapa.buf_seg = ds();
+        /* dapa.lba = 0; */
+
+        ax = 0x4200;            /* Extended Read */
+        si = (size_t)&dapa;
+        dx = devno;
+        asm("pushfl; stc; int $0x13; setc %%al; popfl"
+            : "+a" (ax), "+S" (si), "+d" (dx)
+            : "m" (dapa)
+            : "ebx", "ecx", "edi", "memory");
+
+        if (!(u8)ax)
+                return 0;       /* OK */
+
+        ax = 0x0201;            /* Legacy Read, one sector */
+        cx = 0x0001;            /* Sector 0-0-1 */
+        dx = devno;
+        bx = (size_t)buf;
+        asm("pushfl; stc; int $0x13; setc %%al; popfl"
+            : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)
+            : : "esi", "edi", "memory");
+
+        return -(u8)ax;         /* 0 or -1 */
+}
+
+static u32 read_mbr_sig(u8 devno, struct edd_info *ei)
+{
+        int sector_size;
+        char *mbrbuf_ptr, *mbrbuf_end;
+        u32 mbrsig;
+        u32 buf_base, mbr_base;
+        extern char _end[];
+        static char mbr_buf[1024];
+
+        sector_size = ei->params.bytes_per_sector;
+        if (!sector_size)
+                sector_size = 512; /* Best available guess */
+
+        buf_base = (ds() << 4) + (u32)&_end;
+        mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
+        mbrbuf_ptr = mbr_buf + (mbr_base-buf_base);
+        mbrbuf_end = mbrbuf_ptr + sector_size;
+
+        if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
+                return 0;
+        if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
+                return 0;
+
+        if (read_mbr(devno, mbrbuf_ptr))
+                return 0;
+
+        mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
+        return mbrsig;
+}
+
+static int get_edd_info(u8 devno, struct edd_info *ei)
+{
+        u16 ax, bx, cx, dx, di;
+
+        memset(ei, 0, sizeof *ei);
+
+        /* Check Extensions Present */
+
+        ax = 0x4100;
+        bx = EDDMAGIC1;
+        dx = devno;
+        asm("pushfl; stc; int $0x13; setc %%al; popfl"
+            : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)
+            : : "esi", "edi");
+
+        if ((u8)ax)
+                return -1;      /* No extended information */
+
+        if (bx != EDDMAGIC2)
+                return -1;
+
+        ei->device  = devno;
+        ei->version = ax >> 8;  /* EDD version number */
+        ei->interface_support = cx; /* EDD functionality subsets */
+
+        /* Extended Get Device Parameters */
+
+        ei->params.length = sizeof(ei->params);
+        ax = 0x4800;
+        dx = devno;
+        asm("pushfl; int $0x13; popfl"
+            : "+a" (ax), "+d" (dx)
+            : "S" (&ei->params)
+            : "ebx", "ecx", "edi");
+
+        /* Get legacy CHS parameters */
+
+        /* Ralf Brown recommends setting ES:DI to 0:0 */
+        ax = 0x0800;
+        dx = devno;
+        di = 0;
+        asm("pushw %%es; "
+            "movw %%di,%%es; "
+            "pushfl; stc; int $0x13; setc %%al; popfl; "
+            "popw %%es"
+            : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)
+            : : "esi");
+
+        if ((u8)ax == 0) {
+                ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);
+                ei->legacy_max_head = dx >> 8;
+                ei->legacy_sectors_per_track = cx & 0x3f;
+        }
+
+        return 0;
+}
+
+void query_edd(void)
+{
+        char eddarg[8];
+        int do_mbr = 1;
+        int do_edd = 1;
+        int devno;
+        struct edd_info ei, *edp;
+
+        if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
+                if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip"))
+                        do_mbr = 0;
+                else if (!strcmp(eddarg, "off"))
+                        do_edd = 0;
+        }
+
+        edp = (struct edd_info *)boot_params.eddbuf;
+
+        if (!do_edd)
+                return;
+
+        for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
+                /*
+                 * Scan the BIOS-supported hard disks and query EDD
+                 * information...
+                 */
+                get_edd_info(devno, &ei);
+
+                if (boot_params.eddbuf_entries < EDDMAXNR) {
+                        memcpy(edp, &ei, sizeof ei);
+                        edp++;
+                        boot_params.eddbuf_entries++;
+                }
+
+                if (do_mbr) {
+                        u32 mbr_sig;
+                        mbr_sig = read_mbr_sig(devno, &ei);
+                        boot_params.edd_mbr_sig_buffer[devno-0x80] = mbr_sig;
+                }
+        }
+}
+
+#endif