Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [PATCH v10 11/13] x86/traps: Fixup general protection faults caused by UMIP | Date | Fri, 27 Oct 2017 16:51:48 -0700 |
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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 as follows: if running a 32-bit process, sgdt, sidt and smsw are emulated; str and sldt are not emulated. No emulation is done for 64-bit processes.
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 <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tony Luck <tony.luck@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: x86@kernel.org Reviewed-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- arch/x86/kernel/traps.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index a5791f3..4c0aa6c 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -60,6 +60,7 @@ #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> @@ -514,6 +515,10 @@ 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 (static_cpu_has(X86_FEATURE_UMIP)) + 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); -- 2.7.4
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