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-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of XuYifeng Sent: Tuesday, October 23, 2001 9:00 PM To: [EMAIL PROTECTED] Subject: A stupid question about pmap Hi, I am learning pmap code in FreeBSD 4.4-stable, and confused by some code, for example, in function get_ptbase, the code is: -------- static unsigned * get_ptbase(pmap) pmap_t pmap; { unsigned frame = (unsigned) pmap->pm_pdir[PTDPTDI] & PG_FRAME; /* are we current address space or kernel? */ if (pmap == kernel_pmap || frame == (((unsigned) PTDpde) & PG_FRAME)){ return (unsigned *) PTmap; } /* otherwise, we are alternate address space */ if (frame != (((unsigned) APTDpde) & PG_FRAME)) { APTDpde = (pd_entry_t) (frame | PG_RW | PG_V); #if defined(SMP) /* The page directory is not shared between CPUs */ cpu_invltlb(); #else invltlb(); #endif } return (unsigned *) APTmap; } ----- I know pm_pdir[PTDPTDI] contains page directory page's physical address, while PTDpde is a virtual address to access page directory's page directory entry which is recursivly mapped on virtual address space. question is why could (pmap->pm_pdir[PTDPTDI] & PG_FRAME) and (PTDpde & PG_FRAME) be same thing? a physical address = a virtual address? I am really confused by this. Any help will be appreciated, --- XuYifeng To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-questions" in the body of the message To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
