Segmentation fault to detect resident memory size

Segmentation fault to detect resident memory size

[Mauricio Lin]

Hi all,

I had implemented a new entry in proc directory called smaps for
kernel 2.6.1 and it is working.

I have tried to upgrade it to kernel 2.6.9 but a segmentation fault is
thrown on my shell when I cat the /proc/PID/smaps entry.

Below is the code. It is the same code I had implemented for kernel
2.6.1 but it is not working for kernel 2.6.9. I have done some
debugging and I notice if I comment the instructions after the second
"if statement" the segmentation fault problem is removed. But if I
write a simple printk after it a segmentation fault is invoked.  It is
very strange. I do not know what is going on. Does anyone can help me?


void resident_mem_size(struct mm_struct *mm, unsigned long start_address,
			unsigned long end_address, unsigned long *size) {
	pgd_t *my_pgd;
	pmd_t *my_pmd;
	pte_t *my_pte;
	unsigned long page;

	for (page = start_address; page < end_address; page += PAGE_SIZE) {
		my_pgd = pgd_offset(mm, page);
		if (pgd_none(*my_pgd) || pgd_bad(*my_pgd)) continue;
		my_pmd = pmd_offset(my_pgd, page);
		if (pmd_none(*my_pmd) || pmd_bad(*my_pmd)) continue;
		my_pte = pte_offset_map(my_pmd, page);
		if (pte_present(*my_pte)) {
			*size += PAGE_SIZE;
		}
	  }
}

Mauricio Lin.