Re: [Crash-utility] [PATCH v2] x86_64: Make the conversion between 4level and 5level paging automatically

Hi Dave, At 07/11/2018 03:33 AM, Dave Anderson wrote: I have no idea to check if 5level paging is used in User-space. You gave me some methods, and I have try: -The MAP_FIXED flag -check if the contents of the page directory or p4d is 'flods' Now, I found a rough way. As We all know, in x86_64_uvtop_level4(), the user virtual address is either 4-level or 5-level paging. Can we do like that: if (machdep->flags & VM_5LEVEL) 1) Using 5-level parsing code... 2) Check if it is success If failed, Using 4-level parsing code... else Always using 4-level parsing code... 3) go on... Thanks, dou --------------8<---------------- diff --git a/x86_64.c b/x86_64.c index 07b6aa9..0e12825 100644 --- a/x86_64.c +++ b/x86_64.c @@ -1915,22 +1915,21 @@ x86_64_uvtop_level4(struct task_context *tc, ulong uvaddr, physaddr_t *paddr, in goto no_upage; /* If the VM is in 5-level page table */ - if (machdep->flags & VM_5LEVEL && x86_64_task_uses_5level(tc)) { + if (machdep->flags & VM_5LEVEL) { ulong p4d_pte; /* * p4d = p4d_offset(pgd, address); */ p4d_pte = x86_64_p4d_offset(pgd_pte, uvaddr, verbose, FALSE); - if (!(p4d_pte & _PAGE_PRESENT)) - goto no_upage; - /* - * pud = pud_offset(p4d, address); - */ - pud_pte = x86_64_pud_offset(p4d_pte, uvaddr, verbose, FALSE); + if (!(p4d_pte & _PAGE_PRESENT)) { + /* pud = pud_offset(pgd, address); */ + pud_pte = x86_64_pud_offset(pgd_pte, uvaddr, verbose, FALSE); + } else { + /* pud = pud_offset(p4d, address); */ + pud_pte = x86_64_pud_offset(p4d_pte, uvaddr, verbose, FALSE); + } } else { - /* - * pud = pud_offset(pgd, address); - */ + /* pud = pud_offset(pgd, address); */ pud_pte = x86_64_pud_offset(pgd_pte, uvaddr, verbose, FALSE); }