From: Dave Hansen <[email protected]> The MPX code appears to be saving off the FPU in a potntially unsafe way (if eagerfpu=off). It does not disable preemption or ensure that the FPU state has been allocated. All of the preemption safety comes from the unfortunatley-named 'unlazy_fpu()'.
This patch introduces a new helper which will do both of those things internally. Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: [email protected] Cc: Rik van Riel <[email protected]> Cc: Suresh Siddha <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: the arch/x86 maintainers <[email protected]> --- Changes from v21: * add comments about preemption * rename helper to get_xsave_field_ptr() Changes from "v19": * remove 'tsk' argument to get_xsave_addr() since the code can only realistically work on 'current', and fix up the comment a bit to match. Changes from "v17": * fix s/xstate/xsave_field/ in the function comment * remove EXPORT_SYMBOL_GPL() --- b/arch/x86/include/asm/fpu/xstate.h | 1 + b/arch/x86/kernel/fpu/xstate.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) diff -puN arch/x86/include/asm/fpu/xstate.h~tsk_get_xsave_addr arch/x86/include/asm/fpu/xstate.h --- a/arch/x86/include/asm/fpu/xstate.h~tsk_get_xsave_addr 2015-05-28 08:49:45.191271502 -0700 +++ b/arch/x86/include/asm/fpu/xstate.h 2015-05-29 13:43:34.291184369 -0700 @@ -41,5 +41,6 @@ extern u64 xstate_fx_sw_bytes[USER_XSTAT extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask); void *get_xsave_addr(struct xregs_state *xsave, int xstate); +const void *get_xsave_field_ptr(int xstate_field); #endif diff -puN arch/x86/kernel/fpu/xstate.c~tsk_get_xsave_addr arch/x86/kernel/fpu/xstate.c --- a/arch/x86/kernel/fpu/xstate.c~tsk_get_xsave_addr 2015-05-28 08:49:45.192271546 -0700 +++ b/arch/x86/kernel/fpu/xstate.c 2015-05-29 12:32:47.869662576 -0700 @@ -427,3 +427,35 @@ void *get_xsave_addr(struct xregs_state return (void *)xsave + xstate_comp_offsets[feature_nr]; } EXPORT_SYMBOL_GPL(get_xsave_addr); + +/* + * This wraps up the common operations that need to occur when retrieving + * data from xsave state. It first ensures that the current task was + * using the FPU and retrieves the data in to a buffer. It then calculates + * the offset of the requested field in the buffer. + * + * This function is safe to call whether the FPU is in use or not. + * + * Note that this only works on the current task. + * + * Inputs: + * @xsave_state: state which is defined in xsave.h (e.g. XSTATE_FP, + * XSTATE_SSE, etc...) + * Output: + * address of the state in the xsave area or NULL if the state + * is not present or is in its 'init state'. + */ +const void *get_xsave_field_ptr(int xsave_state) +{ + struct fpu *fpu = ¤t->thread.fpu; + + if (!fpu->fpstate_active) + return NULL; + /* + * fpu__save() takes the CPU's xstate registers + * and saves them off to the 'fpu memory buffer. + */ + fpu__save(fpu); + + return get_xsave_addr(&fpu->xstate->xsave, xsave_state); +} _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
