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    SubjectRe: [PATCH] Make i386 kernel show the segfaults in kernel dmesg, like x86_64.
    Masoud Asgharifard Sharbiani wrote:
    > Hello,
    > This patch makes the i386 behave the same way that x86_64 does when a
    > segfault happens. A line gets printed to the kernel log so that tools
    > that need to check for failures can behave more uniformly between
    > different kernels. Like x86_64, it can be disabled by setting
    > debug.exception-trace sysctl variable to 0 (or by doing
    > echo 0 > /proc/sys/debug/exception-trace)
    >
    > Same behaviour can be extended to other architectures, if needed.
    > cheers,
    > Masoud.
    >
    > Signed-off-by: Masoud Sharbiani <masouds@google.com>
    >
    > diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
    > index 29d7d61..6aa56db 100644
    > --- a/arch/i386/mm/fault.c
    > +++ b/arch/i386/mm/fault.c
    > @@ -283,6 +283,8 @@ static inline int vmalloc_fault(unsigned long address)
    > return 0;
    > }
    >
    > +int exception_trace = 1;
    > +
    > /*
    > * This routine handles page faults. It determines the address,
    > * and the problem, and then passes it off to one of the appropriate
    > @@ -464,7 +466,14 @@ bad_area_nosemaphore:
    > */
    > if (is_prefetch(regs, address, error_code))
    > return;
    > -
    > + if (exception_trace && unhandled_signal(tsk, SIGSEGV)) {
    > + printk(
    > + "%s%s[%d]: segfault at %08lx eip %08lx esp %08lx error %lx\n",
    > + tsk->pid > 1 ? KERN_INFO : KERN_EMERG,
    > + tsk->comm, tsk->pid, address, regs->eip,
    > + regs->esp, error_code);

    Shouldn't we use printk_ratelimit() here, to prevent some nasty person
    from creating some rapidly-segfaulting process that floods the kernel
    logs? (Same with the x86_64 version if it doesn't already..)

    --
    Robert Hancock Saskatoon, SK, Canada
    To email, remove "nospam" from hancockr@nospamshaw.ca
    Home Page: http://www.roberthancock.com/

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