Commit aa9ccb7b authored by Dave Hansen's avatar Dave Hansen Committed by Dave Hansen
Browse files

x86/mpx: remove bounds exception code 



From: Dave Hansen <dave.hansen@linux.intel.com>

MPX is being removed from the kernel due to a lack of support
in the toolchain going forward (gcc).

Remove the other user-visible ABI: signal handling.  This code
should basically have been inactive after the prctl()s were
removed, but there may be some small ABI remnants from this code.
Remove it.

Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
parent 4ba68d00

arch/x86/kernel/traps.c

+0 −74
Original line number Diff line number Diff line
@@ -57,8 +57,6 @@ 
#include <asm/mach_traps.h>

#include <asm/alternative.h>

#include <asm/fpu/xstate.h>

#include <asm/trace/mpx.h>

#include <asm/mpx.h>

#include <asm/vm86.h>

#include <asm/umip.h>
@@ -430,8 +428,6 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign 


dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)

{

	const struct mpx_bndcsr *bndcsr;



	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");

	if (notify_die(DIE_TRAP, "bounds", regs, error_code,

			X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP)
@@ -441,76 +437,6 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) 
	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.

	 * A NULL here might mean that it is in its 'init state',

	 * which is all zeros which indicates MPX was not

	 * responsible for the exception.

	 */

	bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);

	if (!bndcsr)

		goto exit_trap;



	trace_bounds_exception_mpx(bndcsr);

	/*

	 * 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())

			goto exit_trap;

		break; /* Success, it was handled */

	case 1: /* Bound violation. */

	{

		struct task_struct *tsk = current;

		struct mpx_fault_info mpx;



		if (mpx_fault_info(&mpx, regs)) {

			/*

			 * 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 'mpx' containing the address being accessed

		 * which caused the exception.  This information

		 * allows and application to possibly handle the

		 * #BR exception itself.

		 */

		if (!do_trap_no_signal(tsk, X86_TRAP_BR, "bounds", regs,

				       error_code))

			break;



		show_signal(tsk, SIGSEGV, "trap ", "bounds", regs, error_code);



		force_sig_bnderr(mpx.addr, mpx.lower, mpx.upper);

		break;

	}

	case 0: /* No exception caused by Intel MPX operations. */

		goto exit_trap;

	default:

		die("bounds", regs, error_code);

	}



	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, 0, NULL);

}

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