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How to create SIGSEGV at particular memory?

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# 1  
Old 03-24-2011
Question How to create SIGSEGV at particular memory?
Hi
I want to create a SIGSEGV when program tries to access one particular area in memory. Is this possible. If so whats the command.
# 2  
Old 03-24-2011
You can't protect an individual address. You can only protect entire pages -- 4K blocks on PC systems, 8K blocks on some others -- with mprotect. You can call mprotect on any valid memory in your process but it must be on page boundaries.

Code:
char *mem;
// Allocate a page of memory that's guaranteed to be aligned
posix_memalign(&mem, getpagesize(), getpagesize());
// Write A into it
memset(mem, 'A', getpagesize());
// Prevent any access to this memory
mprotect(mem, getpagesize(), PROT_NONE);
// Either a segfault or bus error
printf("mem[0]=%d\n", mem[0]);

# 3  
Old 03-24-2011
Thanks
This is fine. But I want to protect only some byte of memory.
Else is there any way to trigger an function (like HANDLER) when some data been written over that memory?
# 4  
Old 03-24-2011
Quote:
Originally Posted by jionnet
This is fine. But I want to protect only some byte of memory.
Doesn't work that way.

Did you see my suggestion in the other thread of using pointers to pages?
Quote:
Else is there any way to trigger an function (like HANDLER) when some data been written over that memory?
You could use a hardware memory watch in a debugger. These are very limited in capability and system+architecture dependent -- an AMD64 processor running in 64-bit mode can only watch four different 32-bit spots of memory in hardware AFAIK.
# 5  
Old 03-24-2011
Thanks
I'd seen the reply...
I guess that should solve my problem...
I'll come back if some problem hits me.
Thanks again....
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