1 files changed, 84 insertions, 1 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 07ab8e9733c5..a9ae20579895 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -60,6 +60,7 @@
 #include <asm/fixmap.h>
 #include <asm/mach_traps.h>
 #include <asm/alternative.h>
+#include <asm/mpx.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -228,7 +229,6 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	\
 
 DO_ERROR(X86_TRAP_DE,     SIGFPE,  "divide error",              divide_error)
 DO_ERROR(X86_TRAP_OF,     SIGSEGV, "overflow",                  overflow)
-DO_ERROR(X86_TRAP_BR,     SIGSEGV, "bounds",                    bounds)
 DO_ERROR(X86_TRAP_UD,     SIGILL,  "invalid opcode",            invalid_op)
 DO_ERROR(X86_TRAP_OLD_MF, SIGFPE,  "coprocessor segment overrun",coprocessor_segment_overrun)
 DO_ERROR(X86_TRAP_TS,     SIGSEGV, "invalid TSS",               invalid_TSS)
@@ -286,6 +286,89 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
 }
 #endif
 
+dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
+{
+        struct task_struct *tsk = current;
+        struct xsave_struct *xsave_buf;
+        enum ctx_state prev_state;
+        struct bndcsr *bndcsr;
+        siginfo_t *info;
+
+        prev_state = exception_enter();
+        if (notify_die(DIE_TRAP, "bounds", regs, error_code,
+                        X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP)
+                goto exit;
+        conditional_sti(regs);
+
+        if (!user_mode(regs))
+                die("bounds", regs, error_code);
+
+        if (!cpu_feature_enabled(X86_FEATURE_MPX)) {
+                /* The exception is not from Intel MPX */
+                goto exit_trap;
+        }
+
+        /*
+         * We need to look at BNDSTATUS to resolve this exception.
+         * It is not directly accessible, though, so we need to
+         * do an xsave and then pull it out of the xsave buffer.
+         */
+        fpu_save_init(&tsk->thread.fpu);
+        xsave_buf = &(tsk->thread.fpu.state->xsave);
+        bndcsr = get_xsave_addr(xsave_buf, XSTATE_BNDCSR);
+        if (!bndcsr)
+                goto exit_trap;
+
+        /*
+         * The error code field of the BNDSTATUS register communicates status
+         * information of a bound range exception #BR or operation involving
+         * bound directory.
+         */
+        switch (bndcsr->bndstatus & MPX_BNDSTA_ERROR_CODE) {
+        case 2: /* Bound directory has invalid entry. */
+                if (mpx_handle_bd_fault(xsave_buf))
+                        goto exit_trap;
+                break; /* Success, it was handled */
+        case 1: /* Bound violation. */
+                info = mpx_generate_siginfo(regs, xsave_buf);
+                if (PTR_ERR(info)) {
+                        /*
+                         * We failed to decode the MPX instruction.  Act as if
+                         * the exception was not caused by MPX.
+                         */
+                        goto exit_trap;
+                }
+                /*
+                 * Success, we decoded the instruction and retrieved
+                 * an 'info' containing the address being accessed
+                 * which caused the exception.  This information
+                 * allows and application to possibly handle the
+                 * #BR exception itself.
+                 */
+                do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, info);
+                kfree(info);
+                break;
+        case 0: /* No exception caused by Intel MPX operations. */
+                goto exit_trap;
+        default:
+                die("bounds", regs, error_code);
+        }
+
+exit:
+        exception_exit(prev_state);
+        return;
+exit_trap:
+        /*
+         * This path out is for all the cases where we could not
+         * handle the exception in some way (like allocating a
+         * table or telling userspace about it.  We will also end
+         * up here if the kernel has MPX turned off at compile
+         * time..
+         */
+        do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, NULL);
+        exception_exit(prev_state);
+}
+
 dotraplinkage void
 do_general_protection(struct pt_regs *regs, long error_code)
 {