/* * xsave/xrstor support. * * Author: Suresh Siddha */ #include #include #include #include #include #include #include static const char *xfeature_names[] = { "x87 floating point registers" , "SSE registers" , "AVX registers" , "MPX bounds registers" , "MPX CSR" , "AVX-512 opmask" , "AVX-512 Hi256" , "AVX-512 ZMM_Hi256" , "unknown xstate feature" , }; /* * Mask of xstate features supported by the CPU and the kernel: */ u64 xfeatures_mask __read_mostly; /* * Represents init state for the supported extended state. */ struct xsave_struct init_xstate_ctx; static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32; static unsigned int xstate_offsets[XFEATURES_NR_MAX], xstate_sizes[XFEATURES_NR_MAX]; static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8]; /* The number of supported xfeatures in xfeatures_mask: */ static unsigned int xfeatures_nr; /* * Return whether the system supports a given xfeature. * * Also return the name of the (most advanced) feature that the caller requested: */ int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) { u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask; if (unlikely(feature_name)) { long xfeature_idx, max_idx; u64 xfeatures_print; /* * So we use FLS here to be able to print the most advanced * feature that was requested but is missing. So if a driver * asks about "XSTATE_SSE | XSTATE_YMM" we'll print the * missing AVX feature - this is the most informative message * to users: */ if (xfeatures_missing) xfeatures_print = xfeatures_missing; else xfeatures_print = xfeatures_needed; xfeature_idx = fls64(xfeatures_print)-1; max_idx = ARRAY_SIZE(xfeature_names)-1; xfeature_idx = min(xfeature_idx, max_idx); *feature_name = xfeature_names[xfeature_idx]; } if (xfeatures_missing) return 0; return 1; } EXPORT_SYMBOL_GPL(cpu_has_xfeatures); /* * When executing XSAVEOPT (optimized XSAVE), if a processor implementation * detects that an FPU state component is still (or is again) in its * initialized state, it may clear the corresponding bit in the header.xfeatures * field, and can skip the writeout of registers to the corresponding memory layout. * * This means that when the bit is zero, the state component might still contain * some previous - non-initialized register state. * * Before writing xstate information to user-space we sanitize those components, * to always ensure that the memory layout of a feature will be in the init state * if the corresponding header bit is zero. This is to ensure that user-space doesn't * see some stale state in the memory layout during signal handling, debugging etc. */ void __sanitize_i387_state(struct task_struct *tsk) { struct i387_fxsave_struct *fx = &tsk->thread.fpu.state.fxsave; int feature_bit; u64 xfeatures; if (!fx) return; xfeatures = tsk->thread.fpu.state.xsave.header.xfeatures; /* * None of the feature bits are in init state. So nothing else * to do for us, as the memory layout is up to date. */ if ((xfeatures & xfeatures_mask) == xfeatures_mask) return; /* * FP is in init state */ if (!(xfeatures & XSTATE_FP)) { fx->cwd = 0x37f; fx->swd = 0; fx->twd = 0; fx->fop = 0; fx->rip = 0; fx->rdp = 0; memset(&fx->st_space[0], 0, 128); } /* * SSE is in init state */ if (!(xfeatures & XSTATE_SSE)) memset(&fx->xmm_space[0], 0, 256); /* * First two features are FPU and SSE, which above we handled * in a special way already: */ feature_bit = 0x2; xfeatures = (xfeatures_mask & ~xfeatures) >> 2; /* * Update all the remaining memory layouts according to their * standard xstate layout, if their header bit is in the init * state: */ while (xfeatures) { if (xfeatures & 0x1) { int offset = xstate_offsets[feature_bit]; int size = xstate_sizes[feature_bit]; memcpy((void *)fx + offset, (void *)&init_xstate_ctx + offset, size); } xfeatures >>= 1; feature_bit++; } } /* * Check for the presence of extended state information in the * user fpstate pointer in the sigcontext. */ static inline int check_for_xstate(struct i387_fxsave_struct __user *buf, void __user *fpstate, struct _fpx_sw_bytes *fx_sw) { int min_xstate_size = sizeof(struct i387_fxsave_struct) + sizeof(struct xstate_header); unsigned int magic2; if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw))) return -1; /* Check for the first magic field and other error scenarios. */ if (fx_sw->magic1 != FP_XSTATE_MAGIC1 || fx_sw->xstate_size < min_xstate_size || fx_sw->xstate_size > xstate_size || fx_sw->xstate_size > fx_sw->extended_size) return -1; /* * 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 (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)) || magic2 != FP_XSTATE_MAGIC2) return -1; return 0; } /* * Signal frame handlers. */ static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) { if (use_fxsr()) { struct xsave_struct *xsave = &tsk->thread.fpu.state.xsave; struct user_i387_ia32_struct env; struct _fpstate_ia32 __user *fp = buf; convert_from_fxsr(&env, tsk); if (__copy_to_user(buf, &env, sizeof(env)) || __put_user(xsave->i387.swd, &fp->status) || __put_user(X86_FXSR_MAGIC, &fp->magic)) return -1; } else { struct i387_fsave_struct __user *fp = buf; u32 swd; if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status)) return -1; } return 0; } static inline int save_xstate_epilog(void __user *buf, int ia32_frame) { struct xsave_struct __user *x = buf; struct _fpx_sw_bytes *sw_bytes; u32 xfeatures; int err; /* Setup the bytes not touched by the [f]xsave and reserved for SW. */ sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved; err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes)); if (!use_xsave()) return err; err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size)); /* * Read the xfeatures which we copied (directly from the cpu or * from the state in task struct) to the user buffers. */ err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures); /* * 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 * xfeatures in the xsave header. * * xsave aware apps can change the xfeatures in the xsave * header as well as change any contents in the memory layout. * xrestore as part of sigreturn will capture all the changes. */ xfeatures |= XSTATE_FPSSE; err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures); return err; } static inline int save_user_xstate(struct xsave_struct __user *buf) { int err; if (use_xsave()) err = xsave_user(buf); else if (use_fxsr()) err = fxsave_user((struct i387_fxsave_struct __user *) buf); else err = fsave_user((struct i387_fsave_struct __user *) buf); if (unlikely(err) && __clear_user(buf, xstate_size)) err = -EFAULT; return err; } /* * Save the fpu, extended register state to the user signal frame. * * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save * state is copied. * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'. * * buf == buf_fx for 64-bit frames and 32-bit fsave frame. * buf != buf_fx for 32-bit frames with fxstate. * * If the fpu, extended register state is live, save the state directly * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise, * copy the thread's fpu state to the user frame starting at 'buf_fx'. * * If this is a 32-bit frame with fxstate, put a fsave header before * the aligned state at 'buf_fx'. * * For [f]xsave state, update the SW reserved fields in the [f]xsave frame * indicating the absence/presence of the extended state to the user. */ int save_xstate_sig(void __user *buf, void __user *buf_fx, int size) { struct xsave_struct *xsave = ¤t->thread.fpu.state.xsave; struct task_struct *tsk = current; int ia32_fxstate = (buf != buf_fx); ia32_fxstate &= (config_enabled(CONFIG_X86_32) || config_enabled(CONFIG_IA32_EMULATION)); if (!access_ok(VERIFY_WRITE, buf, size)) return -EACCES; if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_get(current, NULL, 0, sizeof(struct user_i387_ia32_struct), NULL, (struct _fpstate_ia32 __user *) buf) ? -1 : 1; if (user_has_fpu()) { /* Save the live register state to the user directly. */ if (save_user_xstate(buf_fx)) return -1; /* Update the thread's fxstate to save the fsave header. */ if (ia32_fxstate) fpu_fxsave(&tsk->thread.fpu); } else { sanitize_i387_state(tsk); if (__copy_to_user(buf_fx, xsave, xstate_size)) return -1; } /* Save the fsave header for the 32-bit frames. */ if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) return -1; if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate)) return -1; return 0; } static inline void sanitize_restored_xstate(struct task_struct *tsk, struct user_i387_ia32_struct *ia32_env, u64 xfeatures, int fx_only) { struct xsave_struct *xsave = &tsk->thread.fpu.state.xsave; struct xstate_header *header = &xsave->header; if (use_xsave()) { /* These bits must be zero. */ memset(header->reserved, 0, 48); /* * Init the state that is not present in the memory * layout and not enabled by the OS. */ if (fx_only) header->xfeatures = XSTATE_FPSSE; else header->xfeatures &= (xfeatures_mask & xfeatures); } if (use_fxsr()) { /* * mscsr reserved bits must be masked to zero for security * reasons. */ xsave->i387.mxcsr &= mxcsr_feature_mask; convert_to_fxsr(tsk, ia32_env); } } /* * Restore the extended state if present. Otherwise, restore the FP/SSE state. */ static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only) { if (use_xsave()) { if ((unsigned long)buf % 64 || fx_only) { u64 init_bv = xfeatures_mask & ~XSTATE_FPSSE; xrstor_state(&init_xstate_ctx, init_bv); return fxrstor_user(buf); } else { u64 init_bv = xfeatures_mask & ~xbv; if (unlikely(init_bv)) xrstor_state(&init_xstate_ctx, init_bv); return xrestore_user(buf, xbv); } } else if (use_fxsr()) { return fxrstor_user(buf); } else return frstor_user(buf); } int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size) { int ia32_fxstate = (buf != buf_fx); struct task_struct *tsk = current; struct fpu *fpu = &tsk->thread.fpu; int state_size = xstate_size; u64 xfeatures = 0; int fx_only = 0; ia32_fxstate &= (config_enabled(CONFIG_X86_32) || config_enabled(CONFIG_IA32_EMULATION)); if (!buf) { fpu_reset_state(fpu); return 0; } if (!access_ok(VERIFY_READ, buf, size)) return -EACCES; fpu__activate_curr(fpu); if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_set(current, NULL, 0, sizeof(struct user_i387_ia32_struct), NULL, buf) != 0; if (use_xsave()) { struct _fpx_sw_bytes fx_sw_user; if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) { /* * Couldn't find the extended state information in the * memory layout. Restore just the FP/SSE and init all * the other extended state. */ state_size = sizeof(struct i387_fxsave_struct); fx_only = 1; } else { state_size = fx_sw_user.xstate_size; xfeatures = fx_sw_user.xfeatures; } } if (ia32_fxstate) { /* * For 32-bit frames with fxstate, copy the user state to the * thread's fpu state, reconstruct fxstate from the fsave * header. Sanitize the copied state etc. */ struct fpu *fpu = &tsk->thread.fpu; struct user_i387_ia32_struct env; int err = 0; /* * Drop the current fpu which clears fpu->fpstate_active. This ensures * that any context-switch during the copy of the new state, * avoids the intermediate state from getting restored/saved. * Thus avoiding the new restored state from getting corrupted. * We will be ready to restore/save the state only after * fpu->fpstate_active is again set. */ drop_fpu(fpu); if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) || __copy_from_user(&env, buf, sizeof(env))) { fpstate_init(fpu); err = -1; } else { sanitize_restored_xstate(tsk, &env, xfeatures, fx_only); } fpu->fpstate_active = 1; if (use_eager_fpu()) { preempt_disable(); fpu__restore(); preempt_enable(); } return err; } else { /* * For 64-bit frames and 32-bit fsave frames, restore the user * state to the registers directly (with exceptions handled). */ user_fpu_begin(); if (restore_user_xstate(buf_fx, xfeatures, fx_only)) { fpu_reset_state(fpu); return -1; } } return 0; } /* * 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 fsave_header_size = sizeof(struct i387_fsave_struct); int size = xstate_size + FP_XSTATE_MAGIC2_SIZE; if (config_enabled(CONFIG_X86_32)) size += fsave_header_size; fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1; fx_sw_reserved.extended_size = size; fx_sw_reserved.xfeatures = xfeatures_mask; fx_sw_reserved.xstate_size = xstate_size; if (config_enabled(CONFIG_IA32_EMULATION)) { fx_sw_reserved_ia32 = fx_sw_reserved; fx_sw_reserved_ia32.extended_size += fsave_header_size; } } /* * Enable the extended processor state save/restore feature. * Called once per CPU onlining. */ void fpu__init_cpu_xstate(void) { if (!cpu_has_xsave || !xfeatures_mask) return; cr4_set_bits(X86_CR4_OSXSAVE); xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask); } /* * Record the offsets and sizes of different state managed by the xsave * memory layout. */ static void __init setup_xstate_features(void) { int eax, ebx, ecx, edx, leaf = 0x2; xfeatures_nr = fls64(xfeatures_mask); do { cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx); if (eax == 0) break; xstate_offsets[leaf] = ebx; xstate_sizes[leaf] = eax; leaf++; } while (1); } static void print_xstate_feature(u64 xstate_mask) { const char *feature_name; if (cpu_has_xfeatures(xstate_mask, &feature_name)) pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name); } /* * Print out all the supported xstate features: */ static void print_xstate_features(void) { print_xstate_feature(XSTATE_FP); print_xstate_feature(XSTATE_SSE); print_xstate_feature(XSTATE_YMM); print_xstate_feature(XSTATE_BNDREGS); print_xstate_feature(XSTATE_BNDCSR); print_xstate_feature(XSTATE_OPMASK); print_xstate_feature(XSTATE_ZMM_Hi256); print_xstate_feature(XSTATE_Hi16_ZMM); } /* * This function sets up offsets and sizes of all extended states in * xsave area. This supports both standard format and compacted format * of the xsave aread. * * Input: void * Output: void */ void setup_xstate_comp(void) { unsigned int xstate_comp_sizes[sizeof(xfeatures_mask)*8]; int i; /* * The FP xstates and SSE xstates are legacy states. They are always * in the fixed offsets in the xsave area in either compacted form * or standard form. */ xstate_comp_offsets[0] = 0; xstate_comp_offsets[1] = offsetof(struct i387_fxsave_struct, xmm_space); if (!cpu_has_xsaves) { for (i = 2; i < xfeatures_nr; i++) { if (test_bit(i, (unsigned long *)&xfeatures_mask)) { xstate_comp_offsets[i] = xstate_offsets[i]; xstate_comp_sizes[i] = xstate_sizes[i]; } } return; } xstate_comp_offsets[2] = FXSAVE_SIZE + XSAVE_HDR_SIZE; for (i = 2; i < xfeatures_nr; i++) { if (test_bit(i, (unsigned long *)&xfeatures_mask)) xstate_comp_sizes[i] = xstate_sizes[i]; else xstate_comp_sizes[i] = 0; if (i > 2) xstate_comp_offsets[i] = xstate_comp_offsets[i-1] + xstate_comp_sizes[i-1]; } } /* * setup the xstate image representing the init state */ static void setup_init_fpu_buf(void) { static int on_boot_cpu = 1; if (!on_boot_cpu) return; on_boot_cpu = 0; if (!cpu_has_xsave) return; setup_xstate_features(); print_xstate_features(); if (cpu_has_xsaves) { init_xstate_ctx.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask; init_xstate_ctx.header.xfeatures = xfeatures_mask; } /* * Init all the features state with header_bv being 0x0 */ xrstor_state_booting(&init_xstate_ctx, -1); /* * Dump the init state again. This is to identify the init state * of any feature which is not represented by all zero's. */ xsave_state_booting(&init_xstate_ctx); } /* * Calculate total size of enabled xstates in XCR0/xfeatures_mask. */ static void __init init_xstate_size(void) { unsigned int eax, ebx, ecx, edx; int i; if (!cpu_has_xsaves) { cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); xstate_size = ebx; return; } xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE; for (i = 2; i < 64; i++) { if (test_bit(i, (unsigned long *)&xfeatures_mask)) { cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); xstate_size += eax; } } } /* * Enable and initialize the xsave feature. * Called once per system bootup. * * ( Not marked __init because of false positive section warnings. ) */ void fpu__init_system_xstate(void) { unsigned int eax, ebx, ecx, edx; static bool on_boot_cpu = 1; if (!on_boot_cpu) return; on_boot_cpu = 0; if (!cpu_has_xsave) { pr_info("x86/fpu: Legacy x87 FPU detected.\n"); return; } if (boot_cpu_data.cpuid_level < XSTATE_CPUID) { WARN(1, "x86/fpu: XSTATE_CPUID missing!\n"); return; } cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); xfeatures_mask = eax + ((u64)edx << 32); if ((xfeatures_mask & XSTATE_FPSSE) != XSTATE_FPSSE) { pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask); BUG(); } /* * Support only the state known to OS. */ xfeatures_mask = xfeatures_mask & XCNTXT_MASK; /* Enable xstate instructions to be able to continue with initialization: */ fpu__init_cpu_xstate(); /* * Recompute the context size for enabled features */ init_xstate_size(); update_regset_xstate_info(xstate_size, xfeatures_mask); prepare_fx_sw_frame(); setup_init_fpu_buf(); pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is 0x%x bytes, using '%s' format.\n", xfeatures_mask, xstate_size, cpu_has_xsaves ? "compacted" : "standard"); } /* * Restore minimal FPU state after suspend: */ void fpu__resume_cpu(void) { /* * Restore XCR0 on xsave capable CPUs: */ if (cpu_has_xsave) xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask); } /* * Given the xsave area and a state inside, this function returns the * address of the state. * * This is the API that is called to get xstate address in either * standard format or compacted format of xsave area. * * Inputs: * xsave: base address of the xsave area; * xstate: state which is defined in xsave.h (e.g. XSTATE_FP, XSTATE_SSE, * etc.) * Output: * address of the state in the xsave area. */ void *get_xsave_addr(struct xsave_struct *xsave, int xstate) { int feature = fls64(xstate) - 1; if (!test_bit(feature, (unsigned long *)&xfeatures_mask)) return NULL; return (void *)xsave + xstate_comp_offsets[feature]; } EXPORT_SYMBOL_GPL(get_xsave_addr);