diff options
Diffstat (limited to 'arch/x86/kernel/xsave.c')
-rw-r--r-- | arch/x86/kernel/xsave.c | 170 |
1 files changed, 152 insertions, 18 deletions
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index a4ae302..9c253bd 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -16,11 +16,88 @@ */ 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; + + BUG_ON(task_thread_info(tsk)->status & TS_USEDFPU); + + 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 upto 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. @@ -102,6 +179,7 @@ int save_i387_xstate(void __user *buf) task_thread_info(tsk)->status &= ~TS_USEDFPU; stts(); } else { + sanitize_i387_state(tsk); if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave, xstate_size)) return -1; @@ -267,11 +345,6 @@ static void prepare_fx_sw_frame(void) #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 @@ -279,37 +352,77 @@ unsigned int sig_xstate_size = sizeof(struct _fpstate); /* * Enable the extended processor state save/restore feature */ -void __cpuinit xsave_init(void) +static inline void xstate_enable(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); } /* + * 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(xstate_size); 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. */ -void __ref xsave_cntxt_init(void) +static void __init xstate_enable_boot_cpu(void) { unsigned int eax, ebx, ecx, edx; - cpuid_count(0xd, 0, &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) { @@ -322,12 +435,13 @@ void __ref xsave_cntxt_init(void) * Support only the state known to OS. */ pcntxt_mask = pcntxt_mask & XCNTXT_MASK; - xsave_init(); + + xstate_enable(); /* * Recompute the context size for enabled features */ - cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx); + cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); xstate_size = ebx; update_regset_xstate_info(xstate_size, pcntxt_mask); @@ -339,3 +453,23 @@ void __ref xsave_cntxt_init(void) "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(); +} |