From 257062b1500733a1e27e59df2166edb8cc8bf9a9 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Wed, 30 Jan 2008 13:33:04 +0100
Subject: [PATCH] --- yaml --- r: 80251 b: refs/heads/master c:
 acd644bb4abb4d9f0ba6b9ec2b356263971ef9d0 h: refs/heads/master i:   80249:
 5c337c260580d77c9443f42a29f839694876d77c   80247:
 518336cf155df30c86719a03299a79a1e0ae9ffd v: v3

---
 [refs]                     |  2 +-
 trunk/arch/x86/boot/main.c | 24 ++++++++++++++++++------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index 0e20a41c2efd..548730be2d68 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1a8514e04e3f0249a75f66225e99cdf48d305be7
+refs/heads/master: acd644bb4abb4d9f0ba6b9ec2b356263971ef9d0
diff --git a/trunk/arch/x86/boot/main.c b/trunk/arch/x86/boot/main.c
index 22ca62ba40c8..7828da5cfd07 100644
--- a/trunk/arch/x86/boot/main.c
+++ b/trunk/arch/x86/boot/main.c
@@ -100,20 +100,32 @@ static void set_bios_mode(void)
 #endif
 }
 
-void main(void)
+static void init_heap(void)
 {
-	/* First, copy the boot header into the "zeropage" */
-	copy_boot_params();
+	char *stack_end;
 
-	/* End of heap check */
 	if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
-		heap_end = (char *)(boot_params.hdr.heap_end_ptr
-				    +0x200-STACK_SIZE);
+		asm("leal %P1(%%esp),%0"
+		    : "=r" (stack_end) : "i" (-STACK_SIZE));
+
+		heap_end = (char *)
+			((size_t)boot_params.hdr.heap_end_ptr + 0x200);
+		if (heap_end > stack_end)
+			heap_end = stack_end;
 	} else {
 		/* Boot protocol 2.00 only, no heap available */
 		puts("WARNING: Ancient bootloader, some functionality "
 		     "may be limited!\n");
 	}
+}
+
+void main(void)
+{
+	/* First, copy the boot header into the "zeropage" */
+	copy_boot_params();
+
+	/* End of heap check */
+	init_heap();
 
 	/* Make sure we have all the proper CPU support */
 	if (validate_cpu()) {