x86: reserve_early end-of-conventional-memory to 1MB, 64-bit

[sfrench/cifs-2.6.git] / arch / x86 / kernel / head64.c

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 24dbf56928d73877969fae6ebff7deb40d3624fe..b684552347df8e80e2e62beec3c40417a551fbfb 100644 (file)
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -49,45 +49,70 @@ static void __init copy_bootdata(char *real_mode_data)
        }
 }
 
-#define EBDA_ADDR_POINTER 0x40E
+#define BIOS_EBDA_SEGMENT 0x40E
+#define BIOS_LOWMEM_KILOBYTES 0x413
 
+/*
+ * The BIOS places the EBDA/XBDA at the top of conventional
+ * memory, and usually decreases the reported amount of
+ * conventional memory (int 0x12) too.
+ */
 static __init void reserve_ebda(void)
 {
-       unsigned ebda_addr, ebda_size;
+       unsigned int lowmem, ebda_addr;
 
-       /*
-        * there is a real-mode segmented pointer pointing to the
-        * 4K EBDA area at 0x40E
-        */
-       ebda_addr = *(unsigned short *)__va(EBDA_ADDR_POINTER);
+       /* end of low (conventional) memory */
+       lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
+       lowmem <<= 10;
+
+       /* start of EBDA area */
+       ebda_addr = *(unsigned short *)__va(BIOS_EBDA_SEGMENT);
        ebda_addr <<= 4;
 
-       if (!ebda_addr)
-               return;
+       /* Fixup: bios puts an EBDA in the top 64K segment */
+       /* of conventional memory, but does not adjust lowmem. */
+       if ((lowmem - ebda_addr) <= 0x10000)
+               lowmem = ebda_addr;
 
-       ebda_size = *(unsigned short *)__va(ebda_addr);
+       /* Fixup: bios does not report an EBDA at all. */
+       /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
+       if ((ebda_addr == 0) && (lowmem >= 0x9f000))
+               lowmem = 0x9f000;
 
-       /* Round EBDA up to pages */
-       if (ebda_size == 0)
-               ebda_size = 1;
-       ebda_size <<= 10;
-       ebda_size = round_up(ebda_size + (ebda_addr & ~PAGE_MASK), PAGE_SIZE);
-       if (ebda_size > 64*1024)
-               ebda_size = 64*1024;
+       /* Paranoia: should never happen, but... */
+       if (lowmem >= 0x100000)
+               lowmem = 0xa0000;
 
-       reserve_early(ebda_addr, ebda_addr + ebda_size, "EBDA");
+       /* reserve all memory between lowmem and the 1MB mark */
+       reserve_early(lowmem, 0x100000, "BIOS reserved");
 }
 
 void __init x86_64_start_kernel(char * real_mode_data)
 {
        int i;
 
+       /*
+        * Build-time sanity checks on the kernel image and module
+        * area mappings. (these are purely build-time and produce no code)
+        */
+       BUILD_BUG_ON(MODULES_VADDR < KERNEL_IMAGE_START);
+       BUILD_BUG_ON(MODULES_VADDR-KERNEL_IMAGE_START < KERNEL_IMAGE_SIZE);
+       BUILD_BUG_ON(MODULES_LEN + KERNEL_IMAGE_SIZE > 2*PUD_SIZE);
+       BUILD_BUG_ON((KERNEL_IMAGE_START & ~PMD_MASK) != 0);
+       BUILD_BUG_ON((MODULES_VADDR & ~PMD_MASK) != 0);
+       BUILD_BUG_ON(!(MODULES_VADDR > __START_KERNEL));
+       BUILD_BUG_ON(!(((MODULES_END - 1) & PGDIR_MASK) ==
+                               (__START_KERNEL & PGDIR_MASK)));
+
        /* clear bss before set_intr_gate with early_idt_handler */
        clear_bss();
 
        /* Make NULL pointers segfault */
        zap_identity_mappings();
 
+       /* Cleanup the over mapped high alias */
+       cleanup_highmap();
+
        for (i = 0; i < IDT_ENTRIES; i++) {
 #ifdef CONFIG_EARLY_PRINTK
                set_intr_gate(i, &early_idt_handlers[i]);