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Full Discussion: Problem about Kernel oops
Top Forums Programming Problem about Kernel oops Post 302588173 by homeboy on Saturday 7th of January 2012 08:39:39 AM
Old 01-07-2012
Problem about Kernel oops

hello,everyone,I'm reading LDD3.Topics about oops,it said the code bellow would cause a fault condition because "this method copies a string to a local variable,unfortunately,the string is longer than the destination array".Well,hard to understand....Is that right?I thought the fault should be caused by the wrong memset,it overwrite the function stack,the value of __user is 0xff now.will anyone tell me what happened here?Thanks;
Code:
size_t fauly_read(struct file *filp, char __user *buf, size_t count, loff_t *pos)
{
      int ret;
      char stack_buf[4];

      memset(stack_buf, 0xff, 20);
      if(count > 4)
           count  = 4;

      ret = copy_to_user(buf, stack_buf, count);
      if(!ret)
          return count;

      return ret;
}

 

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PAPI_remove_events(3)						       PAPI						     PAPI_remove_events(3)

NAME
PAPI_remove_events - Remove an array of hardware event codes from a PAPI event set. SYNOPSIS
Detailed Description A hardware event can be either a PAPI Preset or a native hardware event code. For a list of PAPI preset events, see PAPI_presets or run the papi_avail utility in the PAPI distribution. PAPI Presets can be passed to PAPI_query_event to see if they exist on the underlying architecture. For a list of native events available on current platform, run papi_native_avail in the PAPI distribution. It should be noted that PAPI_remove_events can partially succeed, exactly like PAPI_add_events. C Prototype: #include <papi.h> int PAPI_remove_events( int EventSet, int * EventCode, int number ); Parameters: EventSet an integer handle for a PAPI event set as created by PAPI_create_eventset *Events an array of defined events number an integer indicating the number of events in the array *EventCode Return values: Positive integer The number of consecutive elements that succeeded before the error. PAPI_EINVAL One or more of the arguments is invalid. PAPI_ENOEVST The EventSet specified does not exist. PAPI_EISRUN The EventSet is currently counting events. PAPI_ECNFLCT The underlying counter hardware can not count this event and other events in the EventSet simultaneously. PAPI_ENOEVNT The PAPI preset is not available on the underlying hardware. Example: int EventSet = PAPI_NULL; int Events[] = {PAPI_TOT_INS, PAPI_FP_OPS}; int ret; // Create an empty EventSet ret = PAPI_create_eventset(&EventSet); if (ret != PAPI_OK) handle_error(ret); // Add two events to our EventSet ret = PAPI_add_events(EventSet, Events, 2); if (ret != PAPI_OK) handle_error(ret); // Start counting ret = PAPI_start(EventSet); if (ret != PAPI_OK) handle_error(ret); // Stop counting, ignore values ret = PAPI_stop(EventSet, NULL); if (ret != PAPI_OK) handle_error(ret); // Remove event ret = PAPI_remove_events(EventSet, Events, 2); if (ret != PAPI_OK) handle_error(ret); * @see PAPI_cleanup_eventset PAPI_destroy_eventset PAPI_event_name_to_code PAPI_presets PAPI_add_event PAPI_add_events.fi Author Generated automatically by Doxygen for PAPI from the source code. Version 5.2.0.0 Tue Jun 17 2014 PAPI_remove_events(3)
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