If the User-Mode Instruction Prevention CPU feature is available and enabled, a general protection fault will be issued if the instructions sgdt, sldt, sidt, str or smsw are executed from user-mode context (CPL > 0). If the fault was caused by any of the instructions protected by UMIP, fixup_umip_exception will emulate dummy results for these instructions. If emulation is successful, the result is passed to the user space program and no SIGSEGV signal is emitted.
Please note that fixup_umip_exception also caters for the case when the fault originated while running in virtual-8086 mode. Cc: Andy Lutomirski <[email protected]> Cc: Andrew Morton <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Chen Yucong <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: Huang Rui <[email protected]> Cc: Jiri Slaby <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Michael S. Tsirkin <[email protected]> Cc: Paul Gortmaker <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ravi V. Shankar <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Tony Luck <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Liang Z. Li <[email protected]> Cc: Alexandre Julliard <[email protected]> Cc: Stas Sergeev <[email protected]> Cc: [email protected] Cc: [email protected] Reviewed-by: Andy Lutomirski <[email protected]> Signed-off-by: Ricardo Neri <[email protected]> --- arch/x86/kernel/traps.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 3995d3a..cec548d 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -65,6 +65,7 @@ #include <asm/trace/mpx.h> #include <asm/mpx.h> #include <asm/vm86.h> +#include <asm/umip.h> #ifdef CONFIG_X86_64 #include <asm/x86_init.h> @@ -526,6 +527,9 @@ do_general_protection(struct pt_regs *regs, long error_code) RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); cond_local_irq_enable(regs); + if (user_mode(regs) && fixup_umip_exception(regs)) + return; + if (v8086_mode(regs)) { local_irq_enable(); handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code); -- 2.9.3
