linux.c32: cap the stack pointer to 0xfff0

Linux itself is fine with sp = 0 for a 64K segment, but perhaps other
things aren't.  Just to be safe, set the stack pointer to 64K-16
bytes.

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

diff --git a/com32/lib/syslinux/load_linux.c b/com32/lib/syslinux/load_linux.c
index 6380149..82cef8b 100644 (file)
--- a/com32/lib/syslinux/load_linux.c
+++ b/com32/lib/syslinux/load_linux.c
@@ -483,7 +483,8 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
   regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
   regs.cs = (real_mode_base >> 4)+0x20;
   /* regs.ip = 0; */
-  regs.esp.w[0] = cmdline_offset;
+  /* Linux is OK with sp = 0 = 64K, but perhaps other things aren't... */
+  regs.esp.w[0] = min(cmdline_offset, 0xfff0);
 
 #if DEBUG
   dprintf("Final memory map:\n");