Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hpa/linux-2.6-x86setup

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hpa/linux-2.6-x86setup:
  x86 setup: sizeof() is unsigned, unbreak comparisons
  x86 setup: handle boot loaders which set up the stack incorrectly

5 files changed, 51 insertions, 25 deletions

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 5f9a2e72a731..d2b5adf46512 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -17,6 +17,8 @@
 #ifndef BOOT_BOOT_H
 #define BOOT_BOOT_H
 
+#define STACK_SIZE      512     /* Minimum number of bytes for stack */
+
 #ifndef __ASSEMBLY__
 
 #include <stdarg.h>
@@ -198,8 +200,6 @@ static inline int isdigit(int ch)
 }
 
 /* Heap -- available for dynamic lists. */
-#define STACK_SIZE      512     /* Minimum number of bytes for stack */
-
 extern char _end[];
 extern char *HEAP;
 extern char *heap_end;
@@ -216,9 +216,9 @@ static inline char *__get_heap(size_t s, size_t a, size_t n)
 #define GET_HEAP(type, n) \
         ((type *)__get_heap(sizeof(type),__alignof__(type),(n)))
 
-static inline int heap_free(void)
+static inline bool heap_free(size_t n)
 {
-        return heap_end-HEAP;
+        return (int)(heap_end-HEAP) >= (int)n;
 }
 
 /* copy.S */
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 8353c81c41c0..6ef5a060fa11 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -173,7 +173,8 @@ ramdisk_size:	.long	0		# its size in bytes
 bootsect_kludge:
                 .long   0               # obsolete
 
-heap_end_ptr:   .word   _end+1024       # (Header version 0x0201 or later)
+heap_end_ptr:   .word   _end+STACK_SIZE-512
+                                        # (Header version 0x0201 or later)
                                         # space from here (exclusive) down to
                                         # end of setup code can be used by setup
                                         # for local heap purposes.
@@ -230,28 +231,53 @@ start_of_setup:
         int     $0x13
 #endif
 
-# We will have entered with %cs = %ds+0x20, normalize %cs so
-# it is on par with the other segments.
-        pushw   %ds
-        pushw   $setup2
-        lretw
-
-setup2:
 # Force %es = %ds
         movw    %ds, %ax
         movw    %ax, %es
         cld
 
-# Stack paranoia: align the stack and make sure it is good
-# for both 16- and 32-bit references.  In particular, if we
-# were meant to have been using the full 16-bit segment, the
-# caller might have set %sp to zero, which breaks %esp-based
-# references.
-        andw    $~3, %sp        # dword align (might as well...)
-        jnz     1f
-        movw    $0xfffc, %sp    # Make sure we're not zero
-1:      movzwl  %sp, %esp       # Clear upper half of %esp
-        sti
+# Apparently some ancient versions of LILO invoked the kernel
+# with %ss != %ds, which happened to work by accident for the
+# old code.  If the CAN_USE_HEAP flag is set in loadflags, or
+# %ss != %ds, then adjust the stack pointer.
+
+        # Smallest possible stack we can tolerate
+        movw    $(_end+STACK_SIZE), %cx
+
+        movw    heap_end_ptr, %dx
+        addw    $512, %dx
+        jnc     1f
+        xorw    %dx, %dx        # Wraparound - whole segment available
+1:      testb   $CAN_USE_HEAP, loadflags
+        jnz     2f
+
+        # No CAN_USE_HEAP
+        movw    %ss, %dx
+        cmpw    %ax, %dx        # %ds == %ss?
+        movw    %sp, %dx
+        # If so, assume %sp is reasonably set, otherwise use
+        # the smallest possible stack.
+        jne     4f              # -> Smallest possible stack...
+
+        # Make sure the stack is at least minimum size.  Take a value
+        # of zero to mean "full segment."
+2:
+        andw    $~3, %dx        # dword align (might as well...)
+        jnz     3f
+        movw    $0xfffc, %dx    # Make sure we're not zero
+3:      cmpw    %cx, %dx
+        jnb     5f
+4:      movw    %cx, %dx        # Minimum value we can possibly use
+5:      movw    %ax, %ss
+        movzwl  %dx, %esp       # Clear upper half of %esp
+        sti                     # Now we should have a working stack
+
+# We will have entered with %cs = %ds+0x20, normalize %cs so
+# it is on par with the other segments.
+        pushw   %ds
+        pushw   $6f
+        lretw
+6:
 
 # Check signature at end of setup
         cmpl    $0x5a5aaa55, setup_sig
diff --git a/arch/x86/boot/video-bios.c b/arch/x86/boot/video-bios.c
index 68e65d95cdfd..ed0672a81870 100644
--- a/arch/x86/boot/video-bios.c
+++ b/arch/x86/boot/video-bios.c
@@ -79,7 +79,7 @@ static int bios_probe(void)
         video_bios.modes = GET_HEAP(struct mode_info, 0);
 
         for (mode = 0x14; mode <= 0x7f; mode++) {
-                if (heap_free() < sizeof(struct mode_info))
+                if (!heap_free(sizeof(struct mode_info)))
                         break;
 
                 if (mode_defined(VIDEO_FIRST_BIOS+mode))
diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
index 192190710710..4716b9a96357 100644
--- a/arch/x86/boot/video-vesa.c
+++ b/arch/x86/boot/video-vesa.c
@@ -57,7 +57,7 @@ static int vesa_probe(void)
         while ((mode = rdfs16(mode_ptr)) != 0xffff) {
                 mode_ptr += 2;
 
-                if (heap_free() < sizeof(struct mode_info))
+                if (!heap_free(sizeof(struct mode_info)))
                         break;  /* Heap full, can't save mode info */
 
                 if (mode & ~0x1ff)
diff --git a/arch/x86/boot/video.c b/arch/x86/boot/video.c
index e4ba897bf9a3..ad9712f01739 100644
--- a/arch/x86/boot/video.c
+++ b/arch/x86/boot/video.c
@@ -371,7 +371,7 @@ static void save_screen(void)
         saved.curx = boot_params.screen_info.orig_x;
         saved.cury = boot_params.screen_info.orig_y;
 
-        if (heap_free() < saved.x*saved.y*sizeof(u16)+512)
+        if (!heap_free(saved.x*saved.y*sizeof(u16)+512))
                 return;         /* Not enough heap to save the screen */
 
         saved.data = GET_HEAP(u16, saved.x*saved.y);