Hey all,
This patch builds upon the 4KB stack patch by adding a stack check
debug option. It is set to trigger if less than 512 bytes of the
stack are remaining, and hooks into code by means of gcc's -p option,
which inserts calls to the mcount function. When an overflow is
detected, the code switches to a safety stack, and then proceeds
to dump a backtrace and panic. Comments?
-ben
--
"You will be reincarnated as a toad; and you will be much happier."
:r ~/patches/v2.5.20/v2.5.20-stackcheck-A0.diff
diff -urN smallstack-2.5.20.diff/arch/i386/Makefile stackcheck-2.5.20.diff/arch/i386/Makefile
--- smallstack-2.5.20.diff/arch/i386/Makefile Fri May 31 23:16:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/Makefile Tue Jun 4 21:10:16 2002
@@ -86,6 +86,10 @@
CFLAGS += -march=i586
endif
+ifdef CONFIG_X86_STACK_CHECK
+CFLAGS += -p
+endif
+
HEAD := arch/i386/kernel/head.o arch/i386/kernel/init_task.o
SUBDIRS += arch/i386/kernel arch/i386/mm arch/i386/lib
diff -urN smallstack-2.5.20.diff/arch/i386/boot/compressed/misc.c stackcheck-2.5.20.diff/arch/i386/boot/compressed/misc.c
--- smallstack-2.5.20.diff/arch/i386/boot/compressed/misc.c Mon Nov 12 12:59:43 2001
+++ stackcheck-2.5.20.diff/arch/i386/boot/compressed/misc.c Tue Jun 4 21:11:22 2002
@@ -381,3 +381,7 @@
if (high_loaded) close_output_buffer_if_we_run_high(mv);
return high_loaded;
}
+
+/* We don't actually check for stack overflows this early. */
+__asm__(".globl mcount ; mcount: ret\n");
+
diff -urN smallstack-2.5.20.diff/arch/i386/kernel/i386_ksyms.c stackcheck-2.5.20.diff/arch/i386/kernel/i386_ksyms.c
--- smallstack-2.5.20.diff/arch/i386/kernel/i386_ksyms.c Fri May 31 23:16:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/kernel/i386_ksyms.c Tue Jun 4 21:29:09 2002
@@ -176,3 +176,8 @@
EXPORT_SYMBOL(is_sony_vaio_laptop);
EXPORT_SYMBOL(__PAGE_KERNEL);
+
+#ifdef CONFIG_X86_STACK_CHECK
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
On Tue, Jun 04, 2002 at 11:05:23PM -0400, Benjamin LaHaise wrote:
> Hey all,
>
> This patch builds upon the 4KB stack patch by adding a stack check
> debug option. It is set to trigger if less than 512 bytes of the
> stack are remaining, and hooks into code by means of gcc's -p option,
> which inserts calls to the mcount function. When an overflow is
> detected, the code switches to a safety stack, and then proceeds
> to dump a backtrace and panic. Comments?
Ugh, yet another brown paper bag. -A1 should have the missing hunks.
-ben
:r ~/patches/v2.5.20/v2.5.20-stackcheck-A1.diff
diff -urN smallstack-2.5.20.diff/arch/i386/Makefile stackcheck-2.5.20.diff/arch/i386/Makefile
--- smallstack-2.5.20.diff/arch/i386/Makefile Tue Jun 4 18:00:16 2002
+++ stackcheck-2.5.20.diff/arch/i386/Makefile Tue Jun 4 21:10:16 2002
@@ -86,6 +86,10 @@
CFLAGS += -march=i586
endif
+ifdef CONFIG_X86_STACK_CHECK
+CFLAGS += -p
+endif
+
HEAD := arch/i386/kernel/head.o arch/i386/kernel/init_task.o
SUBDIRS += arch/i386/kernel arch/i386/mm arch/i386/lib
diff -urN smallstack-2.5.20.diff/arch/i386/boot/compressed/misc.c stackcheck-2.5.20.diff/arch/i386/boot/compressed/misc.c
--- smallstack-2.5.20.diff/arch/i386/boot/compressed/misc.c Mon Nov 12 12:59:43 2001
+++ stackcheck-2.5.20.diff/arch/i386/boot/compressed/misc.c Tue Jun 4 21:11:22 2002
@@ -381,3 +381,7 @@
if (high_loaded) close_output_buffer_if_we_run_high(mv);
return high_loaded;
}
+
+/* We don't actually check for stack overflows this early. */
+__asm__(".globl mcount ; mcount: ret\n");
+
diff -urN smallstack-2.5.20.diff/arch/i386/config.in stackcheck-2.5.20.diff/arch/i386/config.in
--- smallstack-2.5.20.diff/arch/i386/config.in Tue Jun 4 23:27:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/config.in Tue Jun 4 21:13:33 2002
@@ -415,6 +415,7 @@
if [ "$CONFIG_HIGHMEM" = "y" ]; then
bool ' Highmem debugging' CONFIG_DEBUG_HIGHMEM
fi
+ bool ' Check for stack overflows' CONFIG_X86_STACK_CHECK
fi
endmenu
diff -urN smallstack-2.5.20.diff/arch/i386/kernel/entry.S stackcheck-2.5.20.diff/arch/i386/kernel/entry.S
--- smallstack-2.5.20.diff/arch/i386/kernel/entry.S Tue Jun 4 23:27:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/kernel/entry.S Tue Jun 4 22:47:27 2002
@@ -563,6 +563,61 @@
pushl $do_spurious_interrupt_bug
jmp error_code
+#ifdef CONFIG_X86_STACK_CHECK
+.data
+ .globl stack_overflowed
+stack_overflowed:
+ .long 0
+
+.text
+
+ENTRY(mcount)
+ push %eax
+ movl $(THREAD_SIZE - 1),%eax
+ andl %esp,%eax
+ cmpl $0x200,%eax /* 512 byte danger zone */
+ jle 1f
+2:
+ popl %eax
+ ret
+1:
+ lock; btsl $0,stack_overflowed /* Prevent reentry via printk */
+ jc 2b
+
+ # switch to overflow stack
+ movl %esp,%eax
+ movl $(stack_overflow_stack + THREAD_SIZE - 4),%esp
+
+ pushf
+ cli
+ pushl %eax
+
+ # push eip then esp of error for stack_overflow_panic
+ pushl 4(%eax)
+ pushl %eax
+
+ # update the task pointer and cpu in the overflow stack's thread_info.
+ GET_THREAD_INFO_WITH_ESP(%eax)
+ movl TI_TASK(%eax),%ebx
+ movl %ebx,stack_overflow_stack+TI_TASK
+ movl TI_CPU(%eax),%ebx
+ movl %ebx,stack_overflow_stack+TI_CPU
+
+ # never neverland
+ call stack_overflow_panic
+
+ addl $8,%esp
+
+ popf
+ popl %eax
+ movl %eax,%esp
+ popl %eax
+ movl $0,stack_overflowed
+ ret
+
+#warning stack check enabled
+#endif
+
.data
ENTRY(sys_call_table)
.long sys_ni_syscall /* 0 - old "setup()" system call*/
diff -urN smallstack-2.5.20.diff/arch/i386/kernel/i386_ksyms.c stackcheck-2.5.20.diff/arch/i386/kernel/i386_ksyms.c
--- smallstack-2.5.20.diff/arch/i386/kernel/i386_ksyms.c Tue Jun 4 18:00:16 2002
+++ stackcheck-2.5.20.diff/arch/i386/kernel/i386_ksyms.c Tue Jun 4 21:29:09 2002
@@ -176,3 +176,8 @@
EXPORT_SYMBOL(is_sony_vaio_laptop);
EXPORT_SYMBOL(__PAGE_KERNEL);
+
+#ifdef CONFIG_X86_STACK_CHECK
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
diff -urN smallstack-2.5.20.diff/arch/i386/kernel/init_task.c stackcheck-2.5.20.diff/arch/i386/kernel/init_task.c
--- smallstack-2.5.20.diff/arch/i386/kernel/init_task.c Tue Jun 4 23:27:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/kernel/init_task.c Tue Jun 4 22:23:10 2002
@@ -16,6 +16,11 @@
union thread_union init_irq_union
__attribute__((__section__(".data.init_task")));
+#ifdef CONFIG_X86_STACK_CHECK
+union thread_union stack_overflow_stack
+ __attribute__((__section__(".data.init_task")));
+#endif
+
/*
* Initial thread structure.
*
diff -urN smallstack-2.5.20.diff/arch/i386/kernel/process.c stackcheck-2.5.20.diff/arch/i386/kernel/process.c
--- smallstack-2.5.20.diff/arch/i386/kernel/process.c Tue Jun 4 23:27:35 2002
+++ stackcheck-2.5.20.diff/arch/i386/kernel/process.c Tue Jun 4 22:13:07 2002
@@ -444,6 +444,16 @@
extern void show_trace(unsigned long* esp);
+#ifdef CONFIG_X86_STACK_CHECK
+void stack_overflow_panic(void *esp, void *eip)
+{
+ printk("stack overflow from %p. esp: %p\n", eip, esp);
+ show_trace(esp);
+ panic("stack overflow\n");
+}
+
+#endif
+
void show_regs(struct pt_regs * regs)
{
unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;