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authorAndy Lutomirski <luto@kernel.org>2017-12-10 22:47:19 -0800
committerIngo Molnar <mingo@kernel.org>2017-12-22 20:13:01 +0100
commit49275fef986abfb8b476e4708aaecc07e7d3e087 (patch)
tree9399ac6f7e74d1422e34de7164d62037fff80c25
parent146122e24bdf208015d629babba673e28d090709 (diff)
downloadlinux-49275fef986abfb8b476e4708aaecc07e7d3e087.tar.bz2
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>
-rw-r--r--arch/x86/entry/vsyscall/vsyscall_64.c34
1 files changed, 33 insertions, 1 deletions
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index f279ba2643dc..daad57c76e42 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -37,6 +37,7 @@
#include <asm/unistd.h>
#include <asm/fixmap.h>
#include <asm/traps.h>
+#include <asm/paravirt.h>
#define CREATE_TRACE_POINTS
#include "vsyscall_trace.h"
@@ -329,16 +330,47 @@ int in_gate_area_no_mm(unsigned long addr)
return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR;
}
+/*
+ * The VSYSCALL page is the only user-accessible page in the kernel address
+ * range. Normally, the kernel page tables can have _PAGE_USER clear, but
+ * the tables covering VSYSCALL_ADDR need _PAGE_USER set if vsyscalls
+ * are enabled.
+ *
+ * Some day we may create a "minimal" vsyscall mode in which we emulate
+ * vsyscalls but leave the page not present. If so, we skip calling
+ * this.
+ */
+static void __init set_vsyscall_pgtable_user_bits(void)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset_k(VSYSCALL_ADDR);
+ set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER));
+ p4d = p4d_offset(pgd, VSYSCALL_ADDR);
+#if CONFIG_PGTABLE_LEVELS >= 5
+ p4d->p4d |= _PAGE_USER;
+#endif
+ pud = pud_offset(p4d, VSYSCALL_ADDR);
+ set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER));
+ pmd = pmd_offset(pud, VSYSCALL_ADDR);
+ set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER));
+}
+
void __init map_vsyscall(void)
{
extern char __vsyscall_page;
unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
- if (vsyscall_mode != NONE)
+ if (vsyscall_mode != NONE) {
__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
vsyscall_mode == NATIVE
? PAGE_KERNEL_VSYSCALL
: PAGE_KERNEL_VVAR);
+ set_vsyscall_pgtable_user_bits();
+ }
BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
(unsigned long)VSYSCALL_ADDR);