Messages in this thread Patch in this message | | | Subject | [PATCH 3/5] x86/mpx: remove bounds exception code | From | Dave Hansen <> | Date | Thu, 23 Jan 2020 11:05:01 -0800 |
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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: Dave Hansen <dave.hansen@linux.intel.com> ---
b/arch/x86/kernel/traps.c | 74 ---------------------------------------------- 1 file changed, 74 deletions(-)
diff -puN arch/x86/kernel/traps.c~mpx-remove-do_bounds arch/x86/kernel/traps.c --- a/arch/x86/kernel/traps.c~mpx-remove-do_bounds 2020-01-23 10:41:05.994942437 -0800 +++ b/arch/x86/kernel/traps.c 2020-01-23 10:41:05.998942437 -0800 @@ -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(struc 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_r 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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