Name: Poison __init regions
Author: Rusty Russell
Status: Experimental

Adds a CONFIG_POISON_INIT and an arch-specific "poison_code()" function.

Index: linux-2.6.10-rc2-bk9-Misc/arch/i386/mm/init.c
===================================================================
--- linux-2.6.10-rc2-bk9-Misc.orig/arch/i386/mm/init.c	2004-11-16 15:29:03.000000000 +1100
+++ linux-2.6.10-rc2-bk9-Misc/arch/i386/mm/init.c	2004-11-27 14:46:00.940942776 +1100
@@ -696,6 +696,20 @@
 	return flag;
 }
 
+#ifdef CONFIG_POISON_INIT
+void poison_mem(void *start, void *end)
+{
+	unsigned short bug_opcode = 0x0b0f, *mem;
+
+	for (mem = start; (void *)mem < end; mem++)
+		*mem = bug_opcode;
+}
+
+void free_initmem(void)
+{
+	poison_mem(&__init_begin, &__init_end);
+}
+#else
 void free_initmem(void)
 {
 	unsigned long addr;
@@ -710,6 +724,7 @@
 	}
 	printk (KERN_INFO "Freeing unused kernel memory: %dk freed\n", (__init_end - __init_begin) >> 10);
 }
+#endif /* CONFIG_POISON_INIT */
 
 #ifdef CONFIG_BLK_DEV_INITRD
 void free_initrd_mem(unsigned long start, unsigned long end)
Index: linux-2.6.10-rc2-bk9-Misc/arch/i386/kernel/module.c
===================================================================
--- linux-2.6.10-rc2-bk9-Misc.orig/arch/i386/kernel/module.c	2004-09-28 16:22:02.000000000 +1000
+++ linux-2.6.10-rc2-bk9-Misc/arch/i386/kernel/module.c	2004-11-27 14:46:00.940942776 +1100
@@ -35,12 +35,17 @@
 	return vmalloc_exec(size);
 }
 
-
 /* Free memory returned from module_alloc */
 void module_free(struct module *mod, void *module_region)
 {
+#ifdef CONFIG_POISON_INIT
+	extern void poison_mem(void *start, void *end);
+	if (module_region == mod->module_init)
+		poison_mem(mod->module_init, mod->module_init+mod->init_size);
+	else
+#endif
 	vfree(module_region);
-	/* FIXME: If module_region == mod->init_region, trim exception
+	/* FIXME: If module_region == mod->module_init, trim exception
            table entries. */
 }
 
Index: linux-2.6.10-rc2-bk9-Misc/arch/i386/Kconfig
===================================================================
--- linux-2.6.10-rc2-bk9-Misc.orig/arch/i386/Kconfig	2004-11-16 15:29:02.000000000 +1100
+++ linux-2.6.10-rc2-bk9-Misc/arch/i386/Kconfig	2004-11-27 14:47:29.556471168 +1100
@@ -35,6 +35,13 @@
 
 source "init/Kconfig"
 
+config DEBUG_POISON_INIT
+	bool "Poison init regions"
+	depends on DEBUG_KERNEL
+	help
+	  Say Y here to have the kernel poison, rather than discard,
+	  init sections in the kernel and modules.
+
 menu "Processor type and features"
 
 choice
Index: linux-2.6.10-rc2-bk9-Misc/include/asm-ppc64/bug.h
===================================================================
--- linux-2.6.10-rc2-bk9-Misc.orig/include/asm-ppc64/bug.h	2004-10-19 14:34:20.000000000 +1000
+++ linux-2.6.10-rc2-bk9-Misc/include/asm-ppc64/bug.h	2004-11-27 14:46:00.941942624 +1100
@@ -1,13 +1,15 @@
 #ifndef _PPC64_BUG_H
 #define _PPC64_BUG_H
+#include <linux/stringify.h>
 
 /*
  * Define an illegal instr to trap on the bug.
  * We don't use 0 because that marks the end of a function
  * in the ELF ABI.  That's "Boo Boo" in case you wonder...
  */
-#define BUG_OPCODE .long 0x00b00b00  /* For asm */
-#define BUG_ILLEGAL_INSTR "0x00b00b00" /* For BUG macro */
+#define BUG_WORD 0x00b00b00
+#define BUG_OPCODE .long BUG_WORD  /* For asm */
+#define BUG_ILLEGAL_INSTR __stringify(BUG_WORD) /* For BUG macro */
 
 #ifndef __ASSEMBLY__
 
Index: linux-2.6.10-rc2-bk9-Misc/arch/ppc64/mm/init.c
===================================================================
--- linux-2.6.10-rc2-bk9-Misc.orig/arch/ppc64/mm/init.c	2004-11-16 15:29:12.000000000 +1100
+++ linux-2.6.10-rc2-bk9-Misc/arch/ppc64/mm/init.c	2004-11-27 14:46:00.941942624 +1100
@@ -441,6 +441,27 @@
 
 #endif
 
+#ifdef CONFIG_POISON_INIT
+void poison_mem(void *start, void *end)
+{
+	unsigned long *mem;
+
+	for (mem = start; (void *)mem < end; mem++)
+		*mem = BUG_WORD;
+}
+
+void free_initmem(void)
+{
+	poison_mem(&__init_begin, &__init_end);
+}
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void free_initrd_mem(unsigned long start, unsigned long end)
+{
+	poison_mem((void *)start, (void *)end);
+}
+#endif
+#else
 void free_initmem(void)
 {
 	unsigned long addr;
@@ -469,6 +490,7 @@
 	}
 }
 #endif
+#endif /* CONFIG_POISON_INIT */
 
 static spinlock_t mmu_context_lock = SPIN_LOCK_UNLOCKED;
 static DEFINE_IDR(mmu_context_idr);