forked from luck/tmp_suning_uos_patched
x86/vsyscall/64: Explicitly set _PAGE_USER in the pagetable hierarchy
The kernel is very erratic as to which pagetables have _PAGE_USER set. The vsyscall page gets lucky: it seems that all of the relevant pagetables are among the apparently arbitrary ones that set _PAGE_USER. Rather than relying on chance, just explicitly set _PAGE_USER. This will let us clean up pagetable setup to stop setting _PAGE_USER. The added code can also be reused by pagetable isolation to manage the _PAGE_USER bit in the usermode tables. [ tglx: Folded paravirt fix from Juergen Gross ] Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Laight <David.Laight@aculab.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -37,6 +37,7 @@
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#include <asm/unistd.h>
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#include <asm/fixmap.h>
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#include <asm/traps.h>
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#include <asm/paravirt.h>
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#define CREATE_TRACE_POINTS
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#include "vsyscall_trace.h"
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@ -329,16 +330,47 @@ int in_gate_area_no_mm(unsigned long addr)
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return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR;
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}
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/*
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* The VSYSCALL page is the only user-accessible page in the kernel address
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* range. Normally, the kernel page tables can have _PAGE_USER clear, but
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* the tables covering VSYSCALL_ADDR need _PAGE_USER set if vsyscalls
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* are enabled.
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*
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* Some day we may create a "minimal" vsyscall mode in which we emulate
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* vsyscalls but leave the page not present. If so, we skip calling
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* this.
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*/
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static void __init set_vsyscall_pgtable_user_bits(void)
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{
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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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pmd_t *pmd;
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pgd = pgd_offset_k(VSYSCALL_ADDR);
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set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
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p4d = p4d_offset(pgd, VSYSCALL_ADDR);
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#if CONFIG_PGTABLE_LEVELS >= 5
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p4d->p4d |= _PAGE_USER;
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#endif
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pud = pud_offset(p4d, VSYSCALL_ADDR);
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set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));
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pmd = pmd_offset(pud, VSYSCALL_ADDR);
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set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER));
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}
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void __init map_vsyscall(void)
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{
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extern char __vsyscall_page;
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unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
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if (vsyscall_mode != NONE)
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if (vsyscall_mode != NONE) {
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__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
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vsyscall_mode == NATIVE
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? PAGE_KERNEL_VSYSCALL
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: PAGE_KERNEL_VVAR);
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set_vsyscall_pgtable_user_bits();
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}
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BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
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(unsigned long)VSYSCALL_ADDR);
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