x86: replace hard coded reservations in 64-bit early boot code with dynamic table

On x86-64 there are several memory allocations before bootmem. To avoid
them stomping on each other they used to be all hard coded in bad_area().
Replace this with an array that is filled as needed.

This cleans up the code considerably and allows to expand its use.

Cc: peterz@infradead.org
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 87e031d4abf1..58438bafedca 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -21,6 +21,7 @@
 #include <asm/tlbflush.h>
 #include <asm/sections.h>
 #include <asm/kdebug.h>
+#include <asm/e820.h>
 
 static void __init zap_identity_mappings(void)
 {
@@ -48,6 +49,35 @@ static void __init copy_bootdata(char *real_mode_data)
         }
 }
 
+#define EBDA_ADDR_POINTER 0x40E
+
+static __init void reserve_ebda(void)
+{
+        unsigned ebda_addr, ebda_size;
+
+        /*
+         * there is a real-mode segmented pointer pointing to the
+         * 4K EBDA area at 0x40E
+         */
+        ebda_addr = *(unsigned short *)__va(EBDA_ADDR_POINTER);
+        ebda_addr <<= 4;
+
+        if (!ebda_addr)
+                return;
+
+        ebda_size = *(unsigned short *)__va(ebda_addr);
+
+        /* 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;
+
+        reserve_early(ebda_addr, ebda_addr + ebda_size);
+}
+
 void __init x86_64_start_kernel(char * real_mode_data)
 {
         int i;
@@ -75,5 +105,23 @@ void __init x86_64_start_kernel(char * real_mode_data)
         pda_init(0);
         copy_bootdata(__va(real_mode_data));
 
+        reserve_early(__pa_symbol(&_text), __pa_symbol(&_end));
+
+        /* Reserve INITRD */
+        if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
+                unsigned long ramdisk_image = boot_params.hdr.ramdisk_image;
+                unsigned long ramdisk_size  = boot_params.hdr.ramdisk_size;
+                unsigned long ramdisk_end   = ramdisk_image + ramdisk_size;
+                reserve_early(ramdisk_image, ramdisk_end);
+        }
+
+        reserve_ebda();
+
+        /*
+         * At this point everything still needed from the boot loader
+         * or BIOS or kernel text should be early reserved or marked not
+         * RAM in e820. All other memory is free game.
+         */
+
         start_kernel();
 }