From a84eeaa96b36a03188e1423349669c108d3a4bd7 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Sun, 7 Jun 2015 11:37:01 -0700 Subject: x86/mpx: Use the new get_xsave_field_ptr()API The MPX registers (bndcsr/bndcfgu/bndstatus) are not directly accessible via normal instructions. They essentially act as if they were floating point registers and are saved/restored along with those registers. There are two main paths in the MPX code where we care about the contents of these registers: 1. #BR (bounds) faults 2. the prctl() code where we are setting MPX up Both of those paths _might_ be called without the FPU having been used. That means that 'tsk->thread.fpu.state' might never be allocated. Also, fpu_save_init() is not preempt-safe. It was a bug to call it without disabling preemption. The new get_xsave_addr() calls unlazy_fpu() instead and properly disables preemption. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Suresh Siddha Cc: bp@alien8.de Link: http://lkml.kernel.org/r/20150607183701.BC0D37CF@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/traps.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) (limited to 'arch/x86/kernel/traps.c') diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index a2510f230195..42f15314b361 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -59,6 +59,7 @@ #include #include #include +#include #include #ifdef CONFIG_X86_64 @@ -371,9 +372,8 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) { struct task_struct *tsk = current; - struct xregs_state *xsave_buf; enum ctx_state prev_state; - struct bndcsr *bndcsr; + const struct bndcsr *bndcsr; siginfo_t *info; prev_state = exception_enter(); @@ -392,12 +392,11 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) /* * 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. + * 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. */ - copy_fpregs_to_fpstate(&tsk->thread.fpu); - xsave_buf = &(tsk->thread.fpu.state.xsave); - bndcsr = get_xsave_addr(xsave_buf, XSTATE_BNDCSR); + bndcsr = get_xsave_field_ptr(XSTATE_BNDCSR); if (!bndcsr) goto exit_trap; @@ -408,11 +407,11 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) */ switch (bndcsr->bndstatus & MPX_BNDSTA_ERROR_CODE) { case 2: /* Bound directory has invalid entry. */ - if (mpx_handle_bd_fault(xsave_buf)) + if (mpx_handle_bd_fault(tsk)) goto exit_trap; break; /* Success, it was handled */ case 1: /* Bound violation. */ - info = mpx_generate_siginfo(regs, xsave_buf); + info = mpx_generate_siginfo(regs, tsk); if (IS_ERR(info)) { /* * We failed to decode the MPX instruction. Act as if -- cgit v1.2.3