Messages in this thread | | | From | gjohnson@research ... | Subject | Resolving physical addresses | Date | Fri, 9 Mar 2001 16:45:28 +1100 (EST) |
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Hi Kernel-dudes,
I have used this snippet of code previously in a 2.2 kernel to get the physical address of the user virtual address 'addr'. It worked fine under 2.2, but gives me crap under 2.4. I have looked at bits of code in the 2.4 memory manager that do similar stuff, and it looks much the same. I call 'mlock' (as root) on the allocated buffer in the user app before my driver gets called to run this code.
I have tried this on a dual CPU system with both a UP and MP kernel.
Is there something that I should be doing different in the 2.4 case, or is maybe 'mlock' broken?
I also used 'map_user_kiobuf' on the same buffer and when I look at iobuf->locked, it says it ain't.
Any ideas, or is there an easier way to get physical address of a user allocated buffer. The kiobuf is a bit obscure to divine from the source.
Regards
Greg.
pgd_t *pgd; /* PaGe Directory */ pmd_t *pmd; /* Page Mid-level Directory */ pte_t *pte; /* Page Table Entry */ unsigned long kern_addr; /* Kernel address of addr. */ unsigned long addr_ofst; /* Offset of addr within a page */
/* Get the page table entry of the page that addr belongs */ pgd = pgd_offset(current->mm, (unsigned long) addr); pmd = pmd_offset(pgd, (unsigned long) addr); pte = pte_offset(pmd, (unsigned long) addr);
/* Calculate the offset of addr within a page and add to kern_addr */ kern_addr = (unsigned long) pte_page(*pte); addr_ofst = addr & (PAGE_SIZE - 1); kern_addr += addr_ofst;
-- +------------------------------------------------------+ | Do you want to know more? www.geocities.com/worfsom/ | | ..ooOO Greg Johnson OOoo.. | | HW/SW Engineer gjohnson@research.canon.com.au | | Canon Information Systems Research Australia (CISRA) | | 1 Thomas Holt Dr., North Ryde, NSW, 2113, Australia | | "I FLEXed my BISON and it went YACC!" - me. | +------------------------------------------------------+
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