/* * xsave/xrstor support. * * Author: Suresh Siddha <suresh.b.siddha@intel.com> */ #include <linux/bootmem.h> #include <linux/compat.h> #include <asm/i387.h> #ifdef CONFIG_IA32_EMULATION #include <asm/sigcontext32.h> #endif #include <asm/xcr.h> /* * Supported feature mask by the CPU and the kernel. */ u64 pcntxt_mask; struct _fpx_sw_bytes fx_sw_reserved; #ifdef CONFIG_IA32_EMULATION struct _fpx_sw_bytes fx_sw_reserved_ia32; #endif /* * Check for the presence of extended state information in the * user fpstate pointer in the sigcontext. */ int check_for_xstate(struct i387_fxsave_struct __user *buf, void __user *fpstate, struct _fpx_sw_bytes *fx_sw_user) { int min_xstate_size = sizeof(struct i387_fxsave_struct) + sizeof(struct xsave_hdr_struct); unsigned int magic2; int err; err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0], sizeof(struct _fpx_sw_bytes)); if (err) return err; /* * First Magic check failed. */ if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1) return -1; /* * Check for error scenarios. */ if (fx_sw_user->xstate_size < min_xstate_size || fx_sw_user->xstate_size > xstate_size || fx_sw_user->xstate_size > fx_sw_user->extended_size) return -1; err = __get_user(magic2, (__u32 *) (((void *)fpstate) + fx_sw_user->extended_size - FP_XSTATE_MAGIC2_SIZE)); /* * Check for the presence of second magic word at the end of memory * layout. This detects the case where the user just copied the legacy * fpstate layout with out copying the extended state information * in the memory layout. */ if (err || magic2 != FP_XSTATE_MAGIC2) return -1; return 0; } #ifdef CONFIG_X86_64 /* * Signal frame handlers. */ int save_i387_xstate(void __user *buf) { struct task_struct *tsk = current; int err = 0; if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size)) return -EACCES; BUG_ON(sig_xstate_size < xstate_size); if ((unsigned long)buf % 64) printk("save_i387_xstate: bad fpstate %p\n", buf); if (!used_math()) return 0; clear_used_math(); /* trigger finit */ if (task_thread_info(tsk)->status & TS_USEDFPU) { /* * Start with clearing the user buffer. This will present a * clean context for the bytes not touched by the fxsave/xsave. */ err = __clear_user(buf, sig_xstate_size); if (err) return err; if (task_thread_info(tsk)->status & TS_XSAVE) err = xsave_user(buf); else err = fxsave_user(buf); if (err) return err; task_thread_info(tsk)->status &= ~TS_USEDFPU; stts(); } else { if (__copy_to_user(buf, &tsk->thread.xstate->fxsave, xstate_size)) return -1; } if (task_thread_info(tsk)->status & TS_XSAVE) { struct _fpstate __user *fx = buf; struct _xstate __user *x = buf; u64 xstate_bv; err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved, sizeof(struct _fpx_sw_bytes)); err |= __put_user(FP_XSTATE_MAGIC2, (__u32 __user *) (buf + sig_xstate_size - FP_XSTATE_MAGIC2_SIZE)); /* * Read the xstate_bv which we copied (directly from the cpu or * from the state in task struct) to the user buffers and * set the FP/SSE bits. */ err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv); /* * For legacy compatible, we always set FP/SSE bits in the bit * vector while saving the state to the user context. This will * enable us capturing any changes(during sigreturn) to * the FP/SSE bits by the legacy applications which don't touch * xstate_bv in the xsave header. * * xsave aware apps can change the xstate_bv in the xsave * header as well as change any contents in the memory layout. * xrestore as part of sigreturn will capture all the changes. */ xstate_bv |= XSTATE_FPSSE; err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv); if (err) return err; } return 1; } /* * Restore the extended state if present. Otherwise, restore the FP/SSE * state. */ int restore_user_xstate(void __user *buf) { struct _fpx_sw_bytes fx_sw_user; u64 mask; int err; if (((unsigned long)buf % 64) || check_for_xstate(buf, buf, &fx_sw_user)) goto fx_only; mask = fx_sw_user.xstate_bv; /* * restore the state passed by the user. */ err = xrestore_user(buf, mask); if (err) return err; /* * init the state skipped by the user. */ mask = pcntxt_mask & ~mask; xrstor_state(init_xstate_buf, mask); return 0; fx_only: /* * couldn't find the extended state information in the * memory layout. Restore just the FP/SSE and init all * the other extended state. */ xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE); return fxrstor_checking((__force struct i387_fxsave_struct *)buf); } /* * This restores directly out of user space. Exceptions are handled. */ int restore_i387_xstate(void __user *buf) { struct task_struct *tsk = current; int err = 0; if (!buf) { if (used_math()) goto clear; return 0; } else if (!access_ok(VERIFY_READ, buf, sig_xstate_size)) return -EACCES; if (!used_math()) { err = init_fpu(tsk); if (err) return err; } if (!(task_thread_info(current)->status & TS_USEDFPU)) { clts(); task_thread_info(current)->status |= TS_USEDFPU; } if (task_thread_info(tsk)->status & TS_XSAVE) err = restore_user_xstate(buf); else err = fxrstor_checking((__force struct i387_fxsave_struct *) buf); if (unlikely(err)) { /* * Encountered an error while doing the restore from the * user buffer, clear the fpu state. */ clear: clear_fpu(tsk); clear_used_math(); } return err; } #endif /* * Prepare the SW reserved portion of the fxsave memory layout, indicating * the presence of the extended state information in the memory layout * pointed by the fpstate pointer in the sigcontext. * This will be saved when ever the FP and extended state context is * saved on the user stack during the signal handler delivery to the user. */ static void prepare_fx_sw_frame(void) { int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) + FP_XSTATE_MAGIC2_SIZE; sig_xstate_size = sizeof(struct _fpstate) + size_extended; #ifdef CONFIG_IA32_EMULATION sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended; #endif memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved)); fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1; fx_sw_reserved.extended_size = sig_xstate_size; fx_sw_reserved.xstate_bv = pcntxt_mask; fx_sw_reserved.xstate_size = xstate_size; #ifdef CONFIG_IA32_EMULATION memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved, sizeof(struct _fpx_sw_bytes)); fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size; #endif } /* * Represents init state for the supported extended state. */ struct xsave_struct *init_xstate_buf; #ifdef CONFIG_X86_64 unsigned int sig_xstate_size = sizeof(struct _fpstate); #endif /* * Enable the extended processor state save/restore feature */ void __cpuinit xsave_init(void) { if (!cpu_has_xsave) return; set_in_cr4(X86_CR4_OSXSAVE); /* * Enable all the features that the HW is capable of * and the Linux kernel is aware of. */ xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask); } /* * setup the xstate image representing the init state */ static void __init setup_xstate_init(void) { init_xstate_buf = alloc_bootmem(xstate_size); init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT; } /* * Enable and initialize the xsave feature. */ void __init xsave_cntxt_init(void) { unsigned int eax, ebx, ecx, edx; cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx); pcntxt_mask = eax + ((u64)edx << 32); if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) { printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n", pcntxt_mask); BUG(); } /* * for now OS knows only about FP/SSE */ pcntxt_mask = pcntxt_mask & XCNTXT_MASK; xsave_init(); /* * Recompute the context size for enabled features */ cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx); xstate_size = ebx; prepare_fx_sw_frame(); setup_xstate_init(); printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, " "cntxt size 0x%x\n", pcntxt_mask, xstate_size); }