[Xen-changelog] [xen-unstable] mini-os: work around ld bug causing stupid CTOR count

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jeremy Fitzhardinge <jeremy@xxxxxxxx>
# Date 1313744262 -3600
# Node ID 9957bef3e7b4511f83ed8883cd5ecd49ea3ee95d
# Parent  e35c5202625ef5534561f84352833ad9467d986c
mini-os: work around ld bug causing stupid CTOR count

I'm seeing pvgrub crashing when running CTORs.  It appears its because
the magic in the linker script is generating junk.  If I get ld to
output a map, I see:

.ctors          0x0000000000097000       0x18
                0x0000000000097000                __CTOR_LIST__ = .
                0x0000000000097000        0x4 LONG 0x25c04
                (((__CTOR_END__ - __CTOR_LIST__) / 0x4) - 0x2)
 *(.ctors)
 .ctors         0x0000000000097004       0x10
                
/home/jeremy/hg/xen/unstable/stubdom/mini-os-x86_32-grub/mini-os.o
                0x0000000000097014        0x4 LONG 0x0
                0x0000000000097018                __CTOR_END__ = .

In other words, somehow ((0x97018-0x97000) / 4) - 2 = 0x25c04

The specific crash is that the ctor loop tries to call the NULL
sentinel.  I'm seeing the same with the DTOR list.

Avoid this by terminating the loop with the NULL sentinel, and get rid
of the CTOR count entirely.

From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Signed-off-by: Keir Fraser <keir@xxxxxxx>
---


diff -r e35c5202625e -r 9957bef3e7b4 extras/mini-os/arch/ia64/minios-ia64.lds
--- a/extras/mini-os/arch/ia64/minios-ia64.lds  Fri Aug 19 09:55:20 2011 +0100
+++ b/extras/mini-os/arch/ia64/minios-ia64.lds  Fri Aug 19 09:57:42 2011 +0100
@@ -55,7 +55,6 @@
   .ctors : AT(ADDR(.ctors) - (((5<<(61))+0x100000000) - (1 << 20)))
        {
         __CTOR_LIST__ = .;
-        QUAD((__CTOR_END__ - __CTOR_LIST__) / 8 - 2)
         *(.ctors)
        CONSTRUCTORS
         QUAD(0)
@@ -65,7 +64,6 @@
   .dtors : AT(ADDR(.dtors) - (((5<<(61))+0x100000000) - (1 << 20)))
         {
         __DTOR_LIST__ = .;
-        QUAD((__DTOR_END__ - __DTOR_LIST__) / 8 - 2)
         *(.dtors)
         QUAD(0)
         __DTOR_END__ = .;
diff -r e35c5202625e -r 9957bef3e7b4 extras/mini-os/arch/x86/minios-x86_32.lds
--- a/extras/mini-os/arch/x86/minios-x86_32.lds Fri Aug 19 09:55:20 2011 +0100
+++ b/extras/mini-os/arch/x86/minios-x86_32.lds Fri Aug 19 09:57:42 2011 +0100
@@ -30,7 +30,6 @@
 
   .ctors : {
         __CTOR_LIST__ = .;
-        LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
         *(.ctors)
        CONSTRUCTORS
         LONG(0)
@@ -39,7 +38,6 @@
 
   .dtors : {
         __DTOR_LIST__ = .;
-        LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2)
         *(.dtors)
         LONG(0)
         __DTOR_END__ = .;
diff -r e35c5202625e -r 9957bef3e7b4 extras/mini-os/arch/x86/minios-x86_64.lds
--- a/extras/mini-os/arch/x86/minios-x86_64.lds Fri Aug 19 09:55:20 2011 +0100
+++ b/extras/mini-os/arch/x86/minios-x86_64.lds Fri Aug 19 09:57:42 2011 +0100
@@ -30,7 +30,6 @@
 
   .ctors : {
         __CTOR_LIST__ = .;
-        QUAD((__CTOR_END__ - __CTOR_LIST__) / 8 - 2)
         *(.ctors)
        CONSTRUCTORS
         QUAD(0)
@@ -39,7 +38,6 @@
 
   .dtors : {
         __DTOR_LIST__ = .;
-        QUAD((__DTOR_END__ - __DTOR_LIST__) / 8 - 2)
         *(.dtors)
         QUAD(0)
         __DTOR_END__ = .;
diff -r e35c5202625e -r 9957bef3e7b4 extras/mini-os/main.c
--- a/extras/mini-os/main.c     Fri Aug 19 09:55:20 2011 +0100
+++ b/extras/mini-os/main.c     Fri Aug 19 09:57:42 2011 +0100
@@ -153,7 +153,7 @@
 
     __libc_init_array();
     environ = envp;
-    for (i = 1; i <= __CTOR_LIST__[0]; i++)
+    for (i = 0; __CTOR_LIST__[i] != 0; i++)
         ((void((*)(void)))__CTOR_LIST__[i]) ();
     tzset();
 
@@ -164,7 +164,7 @@
 {
     int i;
 
-    for (i = 1; i <= __DTOR_LIST__[0]; i++)
+    for (i = 0; __DTOR_LIST__[i] != 0; i++)
         ((void((*)(void)))__DTOR_LIST__[i]) ();
     close_all_files();
     __libc_fini_array();

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