diff options
Diffstat (limited to 'arch/x86/kernel/xsave.c')
| -rw-r--r-- | arch/x86/kernel/xsave.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c new file mode 100644 index 000000000000..9abac8a9d823 --- /dev/null +++ b/arch/x86/kernel/xsave.c @@ -0,0 +1,345 @@ +/* + * 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. + */ +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); +} |