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x86/vsyscall: Show something useful on a read fault

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Just segfaulting the application when it tries to read the vsyscall page in
xonly mode is not helpful for those who need to debug it.

Emit a hint.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jann Horn <jannh@google.com>
Link: https://lkml.kernel.org/r/8016afffe0eab497be32017ad7f6f7030dc3ba66.1561610354.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski
2019-06-26 21:45:04 -07:00
committed by Thomas Gleixner
parent bd49e16e33
commit 918ce32509
3 changed files with 27 additions and 9 deletions
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6
arch/x86/include/asm/vsyscall.h
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@@ -13,10 +13,12 @@ extern void set_vsyscall_pgtable_user_bits(pgd_t *root);
* Called on instruction fetch fault in vsyscall page.
* Returns true if handled.
*/
extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address);
extern bool emulate_vsyscall(unsigned long error_code,
struct pt_regs *regs, unsigned long address);
#else
static inline void map_vsyscall(void) {}
static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
static inline bool emulate_vsyscall(unsigned long error_code,
struct pt_regs *regs, unsigned long address)
{
return false;
}