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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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      Last update: 2005-03-22 13:35    [W:0.035 / U:59.496 seconds]
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