malloc (untested)

[bootcensus] / src / boot / boot2.s

diff --git a/src/boot/boot2.s b/src/boot/boot2.s
index 59096ac..2a163e1 100644 (file)
--- a/src/boot/boot2.s
+++ b/src/boot/boot2.s
@@ -15,6 +15,8 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 # this is the second-stage boot loader
+# plus some other code that needs to run below 1mb (int86 implementation).
+
        .code16
        .section .boot2,"ax"
 
@@ -683,15 +685,21 @@ detect_mem_e801:
        movzx %cx, %eax
        # first size is in KB, convert to bytes
        shl $10, %eax
-       mov %eax, 4(%esi)
-       cmp $0, %dx
+       jnc 0f
+       # overflow means it's >4GB, clamp to 4GB
+       mov $0xffffffff, %eax
+0:     mov %eax, 4(%esi)
        incl boot_mem_map_size
+       cmp $0, %dx
        jz e801_done
        movl $0x1000000, 8(%esi)
        movzx %dx, %eax
        # second size is in 64kb blocks, convert to bytes
        shl $16, %eax
-       mov %eax, 12(%esi)
+       jnc 0f
+       # overflow means it's >4GB, clamp to 4GB
+       mov $0xffffffff, %eax
+0:     mov %eax, 12(%esi)
        incl boot_mem_map_size
 e801_done:
        clc