Support a relocatable ebda segment.

Some option roms will try to relocate the ebda.
Also fix an apparent typo in the assignment of ivecs[0x46].

6 files changed, 47 insertions, 46 deletions

diff --git a/src/ata.c b/src/ata.c
index 53f91963..a8aee7b8 100644
--- a/src/ata.c
+++ b/src/ata.c
@@ -600,20 +600,21 @@ fill_fdpt(int driveid)
     if (driveid > 1)
         return;
 
-    u16 nlc   = GET_EBDA(ata.devices[driveid].lchs.cylinders);
-    u16 nlh   = GET_EBDA(ata.devices[driveid].lchs.heads);
-    u16 nlspt = GET_EBDA(ata.devices[driveid].lchs.spt);
-
-    u16 npc   = GET_EBDA(ata.devices[driveid].pchs.cylinders);
-    u16 nph   = GET_EBDA(ata.devices[driveid].pchs.heads);
-    u16 npspt = GET_EBDA(ata.devices[driveid].pchs.spt);
-
-    SET_EBDA(fdpt[driveid].precompensation, 0xffff);
-    SET_EBDA(fdpt[driveid].drive_control_byte, 0xc0 | ((nph > 8) << 3));
-    SET_EBDA(fdpt[driveid].landing_zone, npc);
-    SET_EBDA(fdpt[driveid].cylinders, nlc);
-    SET_EBDA(fdpt[driveid].heads, nlh);
-    SET_EBDA(fdpt[driveid].sectors, nlspt);
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
+    u16 nlc   = ebda->ata.devices[driveid].lchs.cylinders;
+    u16 nlh   = ebda->ata.devices[driveid].lchs.heads;
+    u16 nlspt = ebda->ata.devices[driveid].lchs.spt;
+
+    u16 npc   = ebda->ata.devices[driveid].pchs.cylinders;
+    u16 nph   = ebda->ata.devices[driveid].pchs.heads;
+    u16 npspt = ebda->ata.devices[driveid].pchs.spt;
+
+    ebda->fdpt[driveid].precompensation = 0xffff;
+    ebda->fdpt[driveid].drive_control_byte = 0xc0 | ((nph > 8) << 3);
+    ebda->fdpt[driveid].landing_zone = npc;
+    ebda->fdpt[driveid].cylinders = nlc;
+    ebda->fdpt[driveid].heads = nlh;
+    ebda->fdpt[driveid].sectors = nlspt;
 
     if (nlc == npc && nlh == nph && nlspt == npspt)
         // no logical CHS mapping used, just physical CHS
@@ -622,17 +623,14 @@ fill_fdpt(int driveid)
 
     // complies with Phoenix style Translated Fixed Disk Parameter
     // Table (FDPT)
-    SET_EBDA(fdpt[driveid].phys_cylinders, npc);
-    SET_EBDA(fdpt[driveid].phys_heads, nph);
-    SET_EBDA(fdpt[driveid].phys_sectors, npspt);
-    SET_EBDA(fdpt[driveid].a0h_signature, 0xa0);
+    ebda->fdpt[driveid].phys_cylinders = npc;
+    ebda->fdpt[driveid].phys_heads = nph;
+    ebda->fdpt[driveid].phys_sectors = npspt;
+    ebda->fdpt[driveid].a0h_signature = 0xa0;
 
     // Checksum structure.
-    u8 *p = MAKE_FARPTR(SEG_EBDA, offsetof(struct extended_bios_data_area_s
-                                           , fdpt[driveid]));
-    u8 sum = checksum(p, FIELD_SIZEOF(struct extended_bios_data_area_s
-                                      , fdpt[driveid]) - 1);
-    SET_EBDA(fdpt[driveid].checksum, -sum);
+    u8 sum = checksum((u8*)&ebda->fdpt[driveid], sizeof(ebda->fdpt[driveid])-1);
+    ebda->fdpt[driveid].checksum = -sum;
 }
 
 static u8
diff --git a/src/biosvar.h b/src/biosvar.h
index f2cb47f6..84c46282 100644
--- a/src/biosvar.h
+++ b/src/biosvar.h
@@ -294,14 +294,19 @@ struct extended_bios_data_area_s {
     u8 resume_stack[128] __aligned(8);
 } PACKED;
 
-#define EBDA_SIZE DIV_ROUND_UP(sizeof(struct extended_bios_data_area_s), 1024)
-#define BASE_MEM_IN_K (640 - EBDA_SIZE)
-
 // Accessor functions
 #define GET_EBDA(var) \
-    GET_FARVAR(SEG_EBDA, ((struct extended_bios_data_area_s *)0)->var)
+    GET_FARVAR(GET_BDA(ebda_seg), ((struct extended_bios_data_area_s *)0)->var)
 #define SET_EBDA(var, val) \
-    SET_FARVAR(SEG_EBDA, ((struct extended_bios_data_area_s *)0)->var, (val))
+    SET_FARVAR(GET_BDA(ebda_seg), ((struct extended_bios_data_area_s *)0)->var, (val))
+static inline struct extended_bios_data_area_s *
+get_ebda_ptr()
+{
+    extern void *__force_link_error__get_ebda_ptr_only_in_32bit();
+    if (MODE16)
+        return __force_link_error__get_ebda_ptr_only_in_32bit();
+    return (void*)MAKE_FARPTR(GET_BDA(ebda_seg), 0);
+}
 
 
 /****************************************************************
diff --git a/src/config.h b/src/config.h
index 1a1499ab..13a023a7 100644
--- a/src/config.h
+++ b/src/config.h
@@ -108,7 +108,6 @@
 
 // Important real-mode segments
 #define SEG_BIOS     0xf000
-#define SEG_EBDA     0x9fc0
 #define SEG_BDA      0x0000
 
 // Segment definitions in protected mode (see rombios32_gdt in romlayout.S)
diff --git a/src/disk.c b/src/disk.c
index 23501ff3..da12d392 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -409,7 +409,7 @@ disk_1348(struct bregs *regs, u8 device)
 
     SET_INT13DPT(regs, size, 30);
 
-    SET_INT13DPT(regs, dpte_segment, SEG_EBDA);
+    SET_INT13DPT(regs, dpte_segment, GET_BDA(ebda_seg));
     SET_INT13DPT(regs, dpte_offset
                  , offsetof(struct extended_bios_data_area_s, ata.dpte));
 
@@ -453,7 +453,7 @@ disk_1348(struct bregs *regs, u8 device)
     SET_EBDA(ata.dpte.reserved, 0);
     SET_EBDA(ata.dpte.revision, 0x11);
 
-    u8 *p = MAKE_FARPTR(SEG_EBDA
+    u8 *p = MAKE_FARPTR(GET_BDA(ebda_seg)
                         , offsetof(struct extended_bios_data_area_s, ata.dpte));
     SET_EBDA(ata.dpte.checksum, -checksum(p, 15));
 
diff --git a/src/optionroms.c b/src/optionroms.c
index 89381634..b7bc1108 100644
--- a/src/optionroms.c
+++ b/src/optionroms.c
@@ -96,10 +96,6 @@ callrom(struct rom_header *rom, u16 offset, u16 bdf)
     call16big(&br);
 
     debug_serial_setup();
-
-    if (GET_BDA(ebda_seg) != SEG_EBDA)
-        BX_PANIC("Option rom at %x:%x attempted to move ebda from %x to %x\n"
-                 , seg, offset, SEG_EBDA, GET_BDA(ebda_seg));
 }
 
 // Verify that an option rom looks valid
@@ -154,14 +150,13 @@ get_pci_rom(struct rom_header *rom)
 static void
 add_ipl(struct rom_header *rom, struct pnp_data *pnp)
 {
-#define ebda ((struct extended_bios_data_area_s *)MAKE_FARPTR(SEG_EBDA, 0))
-
     // Found a device that thinks it can boot the system.  Record
     // its BEV and product name string.
 
     if (! CONFIG_BOOT)
         return;
 
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     if (ebda->ipl.count >= ARRAY_SIZE(ebda->ipl.table))
         return;
 
diff --git a/src/post.c b/src/post.c
index f55d53d0..59516446 100644
--- a/src/post.c
+++ b/src/post.c
@@ -19,7 +19,6 @@
 #include "bregs.h" // struct bregs
 
 #define bda ((struct bios_data_area_s *)MAKE_FARPTR(SEG_BDA, 0))
-#define ebda ((struct extended_bios_data_area_s *)MAKE_FARPTR(SEG_EBDA, 0))
 
 void
 __set_irq(int vector, void *loc)
@@ -39,8 +38,6 @@ init_bda()
     dprintf(3, "init bda\n");
     memset(bda, 0, sizeof(*bda));
 
-    SET_BDA(mem_size_kb, BASE_MEM_IN_K);
-
     // Initialize all vectors to a dummy handler.
     int i;
     for (i=0; i<256; i++)
@@ -78,14 +75,19 @@ init_bda()
 static void
 init_ebda()
 {
+    int esize = DIV_ROUND_UP(sizeof(struct extended_bios_data_area_s), 1024);
+    SET_BDA(mem_size_kb, 640 - esize);
+    u16 eseg = FARPTR_TO_SEG((640 - esize) * 1024);
+    SET_BDA(ebda_seg, eseg);
+
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     memset(ebda, 0, sizeof(*ebda));
-    ebda->size = EBDA_SIZE;
-    SET_BDA(ebda_seg, SEG_EBDA);
-    SET_BDA(ivecs[0x41].seg, SEG_EBDA);
+    ebda->size = esize;
+    SET_BDA(ivecs[0x41].seg, eseg);
     SET_BDA(ivecs[0x41].offset
             , offsetof(struct extended_bios_data_area_s, fdpt[0]));
-    SET_BDA(ivecs[0x46].seg, SEG_EBDA);
-    SET_BDA(ivecs[0x41].offset
+    SET_BDA(ivecs[0x46].seg, eseg);
+    SET_BDA(ivecs[0x46].offset
             , offsetof(struct extended_bios_data_area_s, fdpt[1]));
 }
 
@@ -123,7 +125,8 @@ ram_probe(void)
     add_e820(0xa0000, 0x50000, E820_HOLE);
 
     // Mark known areas as reserved.
-    add_e820((u32)MAKE_FARPTR(SEG_EBDA, 0), EBDA_SIZE * 1024, E820_RESERVED);
+    add_e820((u32)MAKE_FARPTR(GET_BDA(ebda_seg), 0), GET_EBDA(size) * 1024
+             , E820_RESERVED);
     add_e820(BUILD_BIOS_ADDR, BUILD_BIOS_SIZE, E820_RESERVED);
 
     dprintf(1, "ram_size=0x%08x\n", GET_EBDA(ram_size));
@@ -153,6 +156,7 @@ init_boot_vectors()
     dprintf(3, "init boot device ordering\n");
 
     // Floppy drive
+    struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     struct ipl_entry_s *ip = &ebda->ipl.table[0];
     ip->type = IPL_TYPE_FLOPPY;
     ip++;