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SubjectRe: top stack (l)users for 2.5.69
Jörn Engel wrote:
>>The stack overflow checking in -mjb uses gcc's mcount mechanism to
>>detect overflows. It should get called on every single function call.
>
> Nice trick. Do you have better documentation on that machanism than
> man gcc? The paragraph to -p is quite short and I cannot make the
> connection to the rest of the patch immediately.

It is a nice trick, but I didn't write it :) I stole the code from Ben
LaHaise, around 2.5.20. All that I've needed to know to maintain the
patch is that a "jmp mcount" gets placed in the critical places.

I've attached a fairly recent version of the stack check patch. If you
need some more examples, check out kernprof's use of it. It's acg
functionality used mcount as well.
--
Dave Hansen
haveblue@us.ibm.com
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet irqstack-2.5.59-1 -> 1.962
# arch/i386/kernel/process.c 1.32.1.4 -> 1.40
# arch/i386/kernel/irq.c 1.23.1.2 -> 1.26
# Makefile 1.344.2.13 -> 1.349
# include/asm-i386/thread_info.h 1.10.1.4 -> 1.16
# arch/i386/Kconfig 1.13.2.22 -> 1.19
# arch/i386/kernel/entry.S 1.38.1.9 -> 1.53
# arch/i386/Makefile 1.24.2.17 -> 1.33
# arch/i386/boot/compressed/misc.c 1.9.1.1 -> 1.12
# arch/i386/kernel/init_task.c 1.6.1.1 -> 1.8
# arch/i386/kernel/i386_ksyms.c 1.36.2.6 -> 1.44
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/01/27 haveblue@elm3b96.(none) 1.958.1.2
# import new irqstack patch
# covers BUILD_INTERRUPT, as well as common_interrupt
# --------------------------------------------
# 03/01/27 haveblue@elm3b96.(none) 1.961
# Merge elm3b96.(none):/work/dave/bk/linux-2.5-irq-stack
# into elm3b96.(none):/work/dave/bk/linux-2.5-irq-stack+overflow-detect
# --------------------------------------------
# 03/01/27 haveblue@elm3b96.(none) 1.962
# Merge elm3b96.(none):/work/dave/bk/linux-2.5-overflow-detect
# into elm3b96.(none):/work/dave/bk/linux-2.5-irq-stack+overflow-detect
# --------------------------------------------
#
diff -Nru a/arch/i386/Kconfig b/arch/i386/Kconfig
--- a/arch/i386/Kconfig Mon Jan 27 11:40:03 2003
+++ b/arch/i386/Kconfig Mon Jan 27 11:40:03 2003
@@ -1624,6 +1624,25 @@
If you don't debug the kernel, you can say N, but we may not be able
to solve problems without frame pointers.

+config X86_STACK_CHECK
+ bool "Detect stack overflows"
+ depends on FRAME_POINTER
+ help
+ Say Y here to have the kernel attempt to detect when the per-task
+ kernel stack overflows. This is much more robust checking than
+ the above overflow check, which will only occasionally detect
+ an overflow. The level of guarantee here is much greater.
+
+ Some older versions of gcc don't handle the -p option correctly.
+ Kernprof is affected by the same problem, which is described here:
+ http://oss.sgi.com/projects/kernprof/faq.html#Q9
+
+ Basically, if you get oopses in __free_pages_ok during boot when
+ you have this turned on, you need to fix gcc. The Redhat 2.96
+ version and gcc-3.x seem to work.
+
+ If not debugging a stack overflow problem, say N
+
config X86_EXTRA_IRQS
bool
depends on X86_LOCAL_APIC || X86_VOYAGER
diff -Nru a/arch/i386/Makefile b/arch/i386/Makefile
--- a/arch/i386/Makefile Mon Jan 27 11:40:03 2003
+++ b/arch/i386/Makefile Mon Jan 27 11:40:03 2003
@@ -76,6 +76,10 @@
# default subarch .h files
mflags-y += -Iinclude/asm-i386/mach-default

+ifdef CONFIG_X86_STACK_CHECK
+CFLAGS += -p
+endif
+
HEAD := arch/i386/kernel/head.o arch/i386/kernel/init_task.o

libs-y += arch/i386/lib/
diff -Nru a/arch/i386/boot/compressed/misc.c b/arch/i386/boot/compressed/misc.c
--- a/arch/i386/boot/compressed/misc.c Mon Jan 27 11:40:03 2003
+++ b/arch/i386/boot/compressed/misc.c Mon Jan 27 11:40:03 2003
@@ -377,3 +377,7 @@
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 -Nru a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S Mon Jan 27 11:40:03 2003
+++ b/arch/i386/kernel/entry.S Mon Jan 27 11:40:03 2003
@@ -597,6 +597,61 @@
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 $STACK_WARN,%eax /* more than half the stack is used*/
+ jle 1f
+2:
+ popl %eax
+ ret
+1:
+ lock; btsl $0,stack_overflowed
+ 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
+
+ call stack_overflow
+
+ # pop off call arguments
+ addl $8,%esp
+
+ popl %eax
+ popf
+ movl %eax,%esp
+ popl %eax
+ movl $0,stack_overflowed
+ ret
+
+#warning stack check enabled
+#endif
+
.data
ENTRY(sys_call_table)
.long sys_restart_syscall /* 0 - old "setup()" system call, used for restarting */
diff -Nru a/arch/i386/kernel/i386_ksyms.c b/arch/i386/kernel/i386_ksyms.c
--- a/arch/i386/kernel/i386_ksyms.c Mon Jan 27 11:40:03 2003
+++ b/arch/i386/kernel/i386_ksyms.c Mon Jan 27 11:40:03 2003
@@ -214,3 +214,8 @@
EXPORT_SYMBOL(edd);
EXPORT_SYMBOL(eddnr);
#endif
+
+#ifdef CONFIG_X86_STACK_CHECK
+extern void mcount(void);
+EXPORT_SYMBOL(mcount);
+#endif
diff -Nru a/arch/i386/kernel/init_task.c b/arch/i386/kernel/init_task.c
--- a/arch/i386/kernel/init_task.c Mon Jan 27 11:40:03 2003
+++ b/arch/i386/kernel/init_task.c Mon Jan 27 11:40:03 2003
@@ -16,6 +16,10 @@
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 -Nru a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
--- a/arch/i386/kernel/process.c Mon Jan 27 11:40:03 2003
+++ b/arch/i386/kernel/process.c Mon Jan 27 11:40:03 2003
@@ -159,7 +159,22 @@

__setup("idle=", idle_setup);

-void show_regs(struct pt_regs * regs)
+void stack_overflow(unsigned long esp, unsigned long eip)
+{
+ int panicing = ((esp&(THREAD_SIZE-1)) <= STACK_PANIC);
+
+ if (panicing)
+ print_symbol("stack overflow from %s\n", eip);
+ else
+ print_symbol("excessive stack use from %s\n", eip);
+ printk("esp: %p\n", (void*)esp);
+ show_trace((void*)esp);
+
+ if (panicing)
+ panic("stack overflow\n");
+}
+
+asmlinkage void show_regs(struct pt_regs * regs)
{
unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;

diff -Nru a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h
--- a/include/asm-i386/thread_info.h Mon Jan 27 11:40:03 2003
+++ b/include/asm-i386/thread_info.h Mon Jan 27 11:40:03 2003
@@ -63,6 +63,8 @@
*/
#define THREAD_ORDER 1
#define INIT_THREAD_SIZE THREAD_SIZE
+#define STACK_PANIC 0x200ul
+#define STACK_WARN ((THREAD_SIZE)>>1)

#ifndef __ASSEMBLY__
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