/* * xsave/xrstor support. * * Author: Suresh Siddha */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #ifdef CONFIG_IA32_EMULATION #include #endif #include /* * Supported feature mask by the CPU and the kernel. */ u64 pcntxt_mask; /* * Represents init state for the supported extended state. */ static struct xsave_struct *init_xstate_buf; struct _fpx_sw_bytes fx_sw_reserved; #ifdef CONFIG_IA32_EMULATION struct _fpx_sw_bytes fx_sw_reserved_ia32; #endif static unsigned int *xstate_offsets, *xstate_sizes, xstate_features; /* * If a processor implementation discern that a processor state component is * in its initialized state it may modify the corresponding bit in the * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory * layout in the case of xsaveopt. While presenting the xstate information to * the user, we 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 the user doesn't see some stale state in the memory layout during * signal handling, debugging etc. */ void __sanitize_i387_state(struct task_struct *tsk) { u64 xstate_bv; int feature_bit = 0x2; struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave; if (!fx) return; xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv; /* * 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 ((xstate_bv & pcntxt_mask) == pcntxt_mask) return; /* * FP is in init state */ if (!(xstate_bv & 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 (!(xstate_bv & XSTATE_SSE)) memset(&fx->xmm_space[0], 0, 256); xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2; /* * Update all the other memory layouts for which the corresponding * header bit is in the init state. */ while (xstate_bv) { if (xstate_bv & 0x1) { int offset = xstate_offsets[feature_bit]; int size = xstate_sizes[feature_bit]; memcpy(((void *) fx) + offset, ((void *) init_xstate_buf) + offset, size); } xstate_bv >>= 1; feature_bit++; } } /* * 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 -EFAULT; /* * First Magic check failed. */ if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1) return -EINVAL; /* * 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 -EINVAL; err = __get_user(magic2, (__u32 __user *) (fpstate + fx_sw_user->extended_size - FP_XSTATE_MAGIC2_SIZE)); if (err) return err; /* * 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 (magic2 != FP_XSTATE_MAGIC2) return -EFAULT; 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) pr_err("%s: bad fpstate %p\n", __func__, buf); if (!used_math()) return 0; if (user_has_fpu()) { if (use_xsave()) err = xsave_user(buf); else err = fxsave_user(buf); if (unlikely(err)) { __clear_user(buf, xstate_size); return err; } user_fpu_end(); } else { sanitize_i387_state(tsk); if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave, xstate_size)) return -1; } clear_used_math(); /* trigger finit */ if (use_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. */ static 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; if (unlikely(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; } user_fpu_begin(); if (use_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 } #ifdef CONFIG_X86_64 unsigned int sig_xstate_size = sizeof(struct _fpstate); #endif /* * Enable the extended processor state save/restore feature */ static inline void xstate_enable(void) { set_in_cr4(X86_CR4_OSXSAVE); xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_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; xstate_features = fls64(pcntxt_mask); xstate_offsets = alloc_bootmem(xstate_features * sizeof(int)); xstate_sizes = alloc_bootmem(xstate_features * sizeof(int)); 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); } /* * setup the xstate image representing the init state */ static void __init setup_xstate_init(void) { setup_xstate_features(); /* * Setup init_xstate_buf to represent the init state of * all the features managed by the xsave */ init_xstate_buf = alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct)); init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT; clts(); /* * Init all the features state with header_bv being 0x0 */ xrstor_state(init_xstate_buf, -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(init_xstate_buf, -1); stts(); } /* * Enable and initialize the xsave feature. */ static void __init xstate_enable_boot_cpu(void) { unsigned int eax, ebx, ecx, edx; if (boot_cpu_data.cpuid_level < XSTATE_CPUID) { WARN(1, KERN_ERR "XSTATE_CPUID missing\n"); return; } cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); pcntxt_mask = eax + ((u64)edx << 32); if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) { pr_err("FP/SSE not shown under xsave features 0x%llx\n", pcntxt_mask); BUG(); } /* * Support only the state known to OS. */ pcntxt_mask = pcntxt_mask & XCNTXT_MASK; xstate_enable(); /* * Recompute the context size for enabled features */ cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); xstate_size = ebx; update_regset_xstate_info(xstate_size, pcntxt_mask); prepare_fx_sw_frame(); setup_xstate_init(); pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n", pcntxt_mask, xstate_size); } /* * For the very first instance, this calls xstate_enable_boot_cpu(); * for all subsequent instances, this calls xstate_enable(). * * This is somewhat obfuscated due to the lack of powerful enough * overrides for the section checks. */ void __cpuinit xsave_init(void) { static __refdata void (*next_func)(void) = xstate_enable_boot_cpu; void (*this_func)(void); if (!cpu_has_xsave) return; this_func = next_func; next_func = xstate_enable; this_func(); }