Drop support for ACPI 3 E820 extended memory attributes

Drop all support for ACPI 3 E820 extended memory attributes.  There
are BIOSes in the field that report completely bogus information here,
resulting in no memory at all being detected (we then fall back to
E801 detection, but that is problematic in its own ways.)

There is strong reasons to believe at this point that the extended
memory attributes are not usable in their current form, so drop them
and revert back to simple 20-byte support, including for MEMDISK
spoofing.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

10 files changed, 36 insertions, 87 deletions

diff --git a/NEWS b/NEWS
index aadf835d..7acd25b1 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,7 @@ Changes in 3.81:
 	  This unfortunately means that the isohybrid handoff protocol
 	  has changed, so the isohybrid utility must version-match
 	  isolinux.bin.
+	* Drop support for ACPI 3 extended memory flags.
 
 Changes in 3.80:
 	* New shuffler mechanism and API.
diff --git a/com32/lib/syslinux/memscan.c b/com32/lib/syslinux/memscan.c
index 1f9bd8a7..07439207 100644
--- a/com32/lib/syslinux/memscan.c
+++ b/com32/lib/syslinux/memscan.c
@@ -45,7 +45,6 @@ struct e820_entry {
   uint64_t start;
   uint64_t len;
   uint32_t type;
-  uint32_t extattr;
 };
 
 int syslinux_scan_memory(scan_memory_callback_t callback, void *data)
@@ -82,8 +81,6 @@ int syslinux_scan_memory(scan_memory_callback_t callback, void *data)
   ireg.es       = SEG(e820buf);
   ireg.edi.w[0] = OFFS(e820buf);
   memset(e820buf, 0, sizeof *e820buf);
-  /* Set this in case the BIOS doesn't, but doesn't change %ecx to match. */
-  e820buf->extattr = 1;
 
   do {
     __intcall(0x15, &ireg, &oreg);
@@ -93,12 +90,6 @@ int syslinux_scan_memory(scan_memory_callback_t callback, void *data)
 	(oreg.ecx.l < 20))
       break;
 
-    if (oreg.ecx.l < 24)
-      e820buf->extattr = 1;	/* Enabled, normal */
-
-    if (!(e820buf->extattr & 1))
-      continue;
-
     start = e820buf->start;
     len = e820buf->len;
 
diff --git a/com32/mboot/mem.c b/com32/mboot/mem.c
index e9d8bbdb..07ccb627 100644
--- a/com32/mboot/mem.c
+++ b/com32/mboot/mem.c
@@ -42,7 +42,6 @@ struct e820_entry {
   uint64_t start;
   uint64_t len;
   uint32_t type;
-  uint32_t extattr;
 };
 
 #define RANGE_ALLOC_BLOCK	128
@@ -83,8 +82,6 @@ static int mboot_scan_memory(struct AddrRangeDesc **ardp, uint32_t *dosmem)
   ireg.es       = SEG(e820buf);
   ireg.edi.w[0] = OFFS(e820buf);
   memset(e820buf, 0, sizeof *e820buf);
-  /* Set this in case the BIOS doesn't, but doesn't change %ecx to match. */
-  e820buf->extattr = 1;
 
   do {
     __intcall(0x15, &ireg, &oreg);
@@ -94,12 +91,6 @@ static int mboot_scan_memory(struct AddrRangeDesc **ardp, uint32_t *dosmem)
 	(oreg.ecx.l < 20))
       break;
 
-    if (oreg.ecx.l < 24)
-      e820buf->extattr = 1;	/* Enabled, normal */
-
-    if (!(e820buf->extattr & 1))
-      continue;
-
     if (ard_count >= ard_space) {
       ard_space += RANGE_ALLOC_BLOCK;
       *ardp = ard = realloc(ard, ard_space*sizeof *ard);
diff --git a/core/highmem.inc b/core/highmem.inc
index c7e602f8..1f8349bd 100644
--- a/core/highmem.inc
+++ b/core/highmem.inc
@@ -43,9 +43,8 @@ get_e820:
 .start_over:
 		mov di,E820Buf
 		xor ax,ax
-		mov cx,12
+		mov cx,10
 		rep stosw			; Clear buffer
-		mov byte [di-4],01h		; Initial extattr value
 		xor ebx,ebx			; Start with first record
 		jmp short .do_e820		; Skip "at end" check first time!
 .int_loop:	and ebx,ebx			; If we're back at beginning...
@@ -53,7 +52,7 @@ get_e820:
 .do_e820:	mov eax,0000E820h
 		mov edx,534D4150h		; "SMAP" backwards
 		xor ecx,ecx
-		mov cl,24			; ECX <- 24 (size of buffer)
+		mov cl,20			; ECX <- 20 (size of buffer)
 		mov di,E820Buf
 		int 15h
 		jnc .no_carry
@@ -64,15 +63,9 @@ get_e820:
 .no_carry:
 		cmp eax,534D4150h
 		jne no_e820
-		cmp cl,24
-		jb .no_ext_attr
-		;
-		; Some blithering idiot added a whole new field to E820,
-		; completely without regard for its implications...
-		;
-		test byte [E820Buf+20],1	; AddressRangeEnabled
-		jz .not_ram
-.no_ext_attr:
+		cmp cx,20
+		jb no_e820
+
 ;
 ; Look for a memory block starting at <= 1 MB and continuing upward
 ;
@@ -159,7 +152,7 @@ got_highmem:
 
 		section .bss
 		alignb 4
-E820Buf		resd 6			; INT 15:E820 data buffer
+E820Buf		resd 5			; INT 15:E820 data buffer
 E820Mem		resd 1			; Memory detected by E820
 E820Max		resd 1			; Is E820 memory capped?
 HighMemSize	resd 1			; End of memory pointer (bytes)
diff --git a/memdisk/e820.h b/memdisk/e820.h
index 429b98c2..04b44484 100644
--- a/memdisk/e820.h
+++ b/memdisk/e820.h
@@ -21,7 +21,6 @@
 struct e820range {
   uint64_t start;
   uint32_t type;
-  uint32_t extattr;
 } __attribute__((packed));
 
 extern struct e820range ranges[];
@@ -29,6 +28,6 @@ extern int nranges;
 extern uint32_t dos_mem, low_mem, high_mem;
 
 extern void e820map_init(void);
-extern void insertrange(uint64_t, uint64_t, uint32_t, uint32_t);
+extern void insertrange(uint64_t, uint64_t, uint32_t);
 extern void get_mem(void);
 extern void parse_mem(void);
diff --git a/memdisk/e820func.c b/memdisk/e820func.c
index ccfc38ea..80471a9b 100644
--- a/memdisk/e820func.c
+++ b/memdisk/e820func.c
@@ -37,8 +37,7 @@ void e820map_init(void)
   ranges[1].type = -1U;
 }
 
-static void insertrange_at(int where, uint64_t start,
-			   uint32_t type, uint32_t extattr)
+static void insertrange_at(int where, uint64_t start, uint32_t type)
 {
   int i;
 
@@ -47,18 +46,16 @@ static void insertrange_at(int where, uint64_t start,
 
   ranges[where].start   = start;
   ranges[where].type    = type;
-  ranges[where].extattr = extattr;
 
   nranges++;
   ranges[nranges].start   = 0ULL;
   ranges[nranges].type    = -1U;
-  ranges[nranges].extattr = 0;
 }
 
-void insertrange(uint64_t start, uint64_t len, uint32_t type, uint32_t extattr)
+void insertrange(uint64_t start, uint64_t len, uint32_t type)
 {
   uint64_t last;
-  uint32_t oldtype, oldattr;
+  uint32_t oldtype;
   int i, j;
 
   /* Remove this to make len == 0 mean all of memory */
@@ -69,40 +66,34 @@ void insertrange(uint64_t start, uint64_t len, uint32_t type, uint32_t extattr)
 
   i = 0;
   oldtype = -2U;
-  oldattr = 0;
   while ( start > ranges[i].start && ranges[i].type != -1U ) {
     oldtype = ranges[i].type;
-    oldattr = ranges[i].extattr;
     i++;
   }
 
   /* Consider the replacement policy.  This current one is "overwrite." */
 
   if ( start < ranges[i].start || ranges[i].type == -1U )
-    insertrange_at(i++, start, type, extattr);
+    insertrange_at(i++, start, type);
 
   while ( i == 0 || last > ranges[i].start-1 ) {
     oldtype = ranges[i].type;
-    oldattr = ranges[i].extattr;
     ranges[i].type    = type;
-    ranges[i].extattr = extattr;
     i++;
   }
 
   if ( last < ranges[i].start-1 )
-    insertrange_at(i, last+1, oldtype, oldattr);
+    insertrange_at(i, last+1, oldtype);
 
   /* Now the map is correct, but quite possibly not optimal.  Scan the
      map for ranges which are redundant and remove them. */
   i = j = 1;
   oldtype = ranges[0].type;
-  oldattr = ranges[0].extattr;
   while ( i < nranges ) {
-    if ( ranges[i].type == oldtype && ranges[i].extattr == oldattr ) {
+    if ( ranges[i].type == oldtype ) {
       i++;
     } else {
       oldtype = ranges[i].type;
-      oldattr = ranges[i].extattr;
       if ( i != j )
 	ranges[j] = ranges[i];
       i++; j++;
diff --git a/memdisk/e820test.c b/memdisk/e820test.c
index 41fee007..2de7fd4e 100644
--- a/memdisk/e820test.c
+++ b/memdisk/e820test.c
@@ -36,17 +36,17 @@ void printranges(void) {
   int i;
 
   for ( i = 0 ; i < nranges ; i++ ) {
-    printf("%016llx %016llx %d %x\n",
+    printf("%016llx %016llx %d\n",
 	   ranges[i].start,
 	   ranges[i+1].start - ranges[i].start,
-	   ranges[i].type, ranges[i].extattr);
+	   ranges[i].type);
   }
 }
 
 int main(void)
 {
   uint64_t start, len;
-  uint32_t type, extattr;
+  uint32_t type;
   char line[BUFSIZ], *p;
 
   e820map_init();
@@ -55,12 +55,11 @@ int main(void)
   while ( fgets(line, BUFSIZ, stdin) ) {
     p = strchr(line, ':');
     p = p ? p+1 : line;
-    extattr = 1;
-    if ( sscanf(p, " %llx %llx %d %x", &start, &len, &type, &extattr) >= 3 ) {
+    if ( sscanf(p, " %llx %llx %d", &start, &len, &type) == 3 ) {
       putchar('\n');
-      printf("%016llx %016llx %d %x <-\n", start, len, type, extattr);
+      printf("%016llx %016llx %d <-\n", start, len, type);
       putchar('\n');
-      insertrange(start, len, type, extattr);
+      insertrange(start, len, type);
       printranges();
     }
   }
diff --git a/memdisk/memdisk.inc b/memdisk/memdisk.inc
index fa4fe3e5..00537a83 100644
--- a/memdisk/memdisk.inc
+++ b/memdisk/memdisk.inc
@@ -540,26 +540,19 @@ int15_e820:
 		jne .renew
 		mov ebx,E820Table
 .renew:
-		add bx,16		; Advance to next
-		mov eax,[bx-8]		; Type
+		add bx,12		; Advance to next
+		mov eax,[bx-4]		; Type
 		and eax,eax		; Null type?
 		jz .renew		; If so advance to next
 		mov [es:di+16],eax
-		and cl,~3
-		cmp ecx,24
-		jb .no_extattr
-		mov eax,[bx-4]		; Extended attributes
-		mov [es:di+20],eax
-		mov ecx,24		; Bytes loaded
-.no_extattr:
-		mov eax,[bx-16]		; Start addr (low)
-		mov edx,[bx-12]		; Start addr (high)
+		mov eax,[bx-12]		; Start addr (low)
+		mov edx,[bx-8]		; Start addr (high)
 		mov [es:di],eax
 		mov [es:di+4],edx
 		mov eax,[bx]		; End addr (low)
 		mov edx,[bx+4]		; End addr (high)
-		sub eax,[bx-16]		; Derive the length
-		sbb edx,[bx-12]
+		sub eax,[bx-12]		; Derive the length
+		sbb edx,[bx-8]
 		mov [es:di+8],eax	; Length (low)
 		mov [es:di+12],edx	; Length (high)
 		cmp dword [bx+8],-1	; Type of next = end?
@@ -568,6 +561,7 @@ int15_e820:
 .notdone:
 		pop eax			; "SMAP"
 		mov edx,eax		; Some systems expect eax = edx = SMAP
+		mov ecx,20		; Bytes loaded
 		pop ds
 int15_success:
 		mov byte [bp+6], 02h	; Clear CF
diff --git a/memdisk/msetup.c b/memdisk/msetup.c
index a2067011..e5111174 100644
--- a/memdisk/msetup.c
+++ b/memdisk/msetup.c
@@ -38,7 +38,6 @@ static inline int get_e820(void)
     uint64_t base;
     uint64_t len;
     uint32_t type;
-    uint32_t extattr;
   } *buf = sys_bounce;
   uint32_t copied;
   int range_count = 0;
@@ -46,7 +45,6 @@ static inline int get_e820(void)
 
   memset(&regs, 0, sizeof regs);
   memset(buf, 0, sizeof *buf);
-  buf->extattr = 1;
 
   do {
     regs.eax.l = 0x0000e820;
@@ -61,18 +59,12 @@ static inline int get_e820(void)
     if ( regs.eax.l != 0x534d4150 || copied < 20 )
       break;
 
-    if ( copied < 24 )
-      buf->extattr = 1;
-
-    printf("e820: %08x%08x %08x%08x %d [%x]\n",
+    printf("e820: %08x%08x %08x%08x %d\n",
 	   (uint32_t)(buf->base >> 32), (uint32_t)buf->base,
 	   (uint32_t)(buf->len >> 32), (uint32_t)buf->len,
-	   buf->type, buf->extattr);
-
-    if ( !(buf->extattr & 1) )
-      continue;			/* Disabled range, just ignore */
+	   buf->type);
 
-    insertrange(buf->base, buf->len, buf->type, buf->extattr);
+    insertrange(buf->base, buf->len, buf->type);
     range_count++;
 
   } while ( regs.ebx.l );
@@ -86,7 +78,7 @@ static inline void get_dos_mem(void)
 
   memset(&regs, 0, sizeof regs);
   syscall(0x12, &regs, &regs);
-  insertrange(0, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1, 1);
+  insertrange(0, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1);
   printf(" DOS: %d K\n", regs.eax.w[0]);
 }
 
@@ -102,10 +94,10 @@ static inline int get_e801(void)
 
   if ( !(err = regs.eflags.l & 1) ) {
     if ( regs.eax.w[0] ) {
-      insertrange(0x100000, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1, 1);
+      insertrange(0x100000, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1);
     }
     if ( regs.ebx.w[0] ) {
-      insertrange(0x1000000, (uint64_t)((uint32_t)regs.ebx.w[0] << 16), 1, 1);
+      insertrange(0x1000000, (uint64_t)((uint32_t)regs.ebx.w[0] << 16), 1);
     }
 
     printf("e801: %04x %04x\n", regs.eax.w[0], regs.ebx.w[0]);
@@ -127,7 +119,7 @@ static inline int get_88(void)
 
   if ( !(err = regs.eflags.l & 1) ) {
     if ( regs.eax.w[0] ) {
-      insertrange(0x100000, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1, 1);
+      insertrange(0x100000, (uint64_t)((uint32_t)regs.eax.w[0] << 10), 1);
     }
 
     printf("  88: %04x\n", regs.eax.w[0]);
diff --git a/memdisk/setup.c b/memdisk/setup.c
index 61f9bfb5..94a80113 100644
--- a/memdisk/setup.c
+++ b/memdisk/setup.c
@@ -295,8 +295,6 @@ void unzip_if_needed(uint32_t *where_p, uint32_t *size_p)
       /* Must be memory */
       if ( ranges[i].type != 1 )
 	continue;
-      if (!(ranges[i].extattr & 1))
-	continue;
 
       /* Range start */
       if ( ranges[i].start >= 0xFFFFFFFF )
@@ -752,7 +750,7 @@ __cdecl void setup(__cdecl syscall_t cs_syscall, void *cs_bounce)
   }
 
   /* Reserve the ramdisk memory */
-  insertrange(ramdisk_image, ramdisk_size, 2, 1);
+  insertrange(ramdisk_image, ramdisk_size, 2);
   parse_mem();			/* Recompute variables */
 
   /* Figure out where it needs to go */
@@ -896,7 +894,7 @@ __cdecl void setup(__cdecl syscall_t cs_syscall, void *cs_bounce)
 
   /* Reserve this range of memory */
   wrz_16(BIOS_BASEMEM, driveraddr >> 10);
-  insertrange(driveraddr, dos_mem-driveraddr, 2, 1);
+  insertrange(driveraddr, dos_mem-driveraddr, 2);
   parse_mem();
 
   pptr->mem1mb     = low_mem  >> 10;