x86, reboot: Fix relocations in reboot_32.S

The use of base for %ebx in this file is arbitrary, *except* that we
also use it to compute the real-mode segment.  Therefore, make it so
that r_base really is the true address to which %ebx points.

This resolves kernel bugzilla 33302.

Reported-and-tested-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/n/tip-08os5wi3yq1no0y4i5m4z7he@git.kernel.org

diff --git a/arch/x86/kernel/reboot_32.S b/arch/x86/kernel/reboot_32.S
index 29092b38d816ee2577e5e89fb74cc023dbafc411..1d5c46df0d787abc497a1d025a9a8fd2cd347026 100644 (file)
--- a/arch/x86/kernel/reboot_32.S
+++ b/arch/x86/kernel/reboot_32.S
@@ -21,26 +21,26 @@ r_base = .
        /* Get our own relocated address */
        call    1f
 1:     popl    %ebx
-       subl    $1b, %ebx
+       subl    $(1b - r_base), %ebx
 
        /* Compute the equivalent real-mode segment */
        movl    %ebx, %ecx
        shrl    $4, %ecx
        
        /* Patch post-real-mode segment jump */
-       movw    dispatch_table(%ebx,%eax,2),%ax
-       movw    %ax, 101f(%ebx)
-       movw    %cx, 102f(%ebx)
+       movw    (dispatch_table - r_base)(%ebx,%eax,2),%ax
+       movw    %ax, (101f - r_base)(%ebx)
+       movw    %cx, (102f - r_base)(%ebx)
 
        /* Set up the IDT for real mode. */
-       lidtl   machine_real_restart_idt(%ebx)
+       lidtl   (machine_real_restart_idt - r_base)(%ebx)
 
        /*
         * Set up a GDT from which we can load segment descriptors for real
         * mode.  The GDT is not used in real mode; it is just needed here to
         * prepare the descriptors.
         */
-       lgdtl   machine_real_restart_gdt(%ebx)
+       lgdtl   (machine_real_restart_gdt - r_base)(%ebx)
 
        /*
         * Load the data segment registers with 16-bit compatible values