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Jvrn 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--=_courier-15668-1052338587-0001-2 Content-Type: text/plain; name="C-stack_usage_check-2.5.59-8.patch"; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="C-stack_usage_check-2.5.59-8.patch"
# 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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