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* xsave/xrstor support.
*
* Author: Suresh Siddha <suresh.b.siddha@intel.com>
*/
#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/pkeys.h>
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/regset.h>
#include <asm/tlbflush.h>
/*
* Although we spell it out in here, the Processor Trace
* xfeature is completely unused. We use other mechanisms
* to save/restore PT state in Linux.
*/
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" ,
"Processor Trace (unused)" ,
"Protection Keys User registers",
"unknown xstate feature" ,
};
/*
* Mask of xstate features supported by the CPU and the kernel:
*/
u64 xfeatures_mask __read_mostly;
static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_sizes[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
/*
* Clear all of the X86_FEATURE_* bits that are unavailable
* when the CPU has no XSAVE support.
*/
void fpu__xstate_clear_all_cpu_caps(void)
{
setup_clear_cpu_cap(X86_FEATURE_XSAVE);
setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
setup_clear_cpu_cap(X86_FEATURE_XSAVES);
setup_clear_cpu_cap(X86_FEATURE_AVX);
setup_clear_cpu_cap(X86_FEATURE_AVX2);
setup_clear_cpu_cap(X86_FEATURE_AVX512F);
setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
setup_clear_cpu_cap(X86_FEATURE_AVX512DQ);
setup_clear_cpu_cap(X86_FEATURE_AVX512BW);
setup_clear_cpu_cap(X86_FEATURE_AVX512VL);
setup_clear_cpu_cap(X86_FEATURE_MPX);
setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
setup_clear_cpu_cap(X86_FEATURE_PKU);
}
/*
* 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 "XFEATURE_MASK_SSE | XFEATURE_MASK_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 (or other optimized XSAVE instructions), 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 fpstate_sanitize_xstate(struct fpu *fpu)
{
struct fxregs_state *fx = &fpu->state.fxsave;
int feature_bit;
u64 xfeatures;
if (!use_xsaveopt())
return;
xfeatures = 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 & XFEATURE_MASK_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 & XFEATURE_MASK_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_fpstate.xsave + offset,
size);
}
xfeatures >>= 1;
feature_bit++;
}
}
/*
* Enable the extended processor state save/restore feature.
* Called once per CPU onlining.
*/
void fpu__init_cpu_xstate(void)
{
if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
return;
cr4_set_bits(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}
/*
* Note that in the future we will likely need a pair of
* functions here: one for user xstates and the other for
* system xstates. For now, they are the same.
*/
static int xfeature_enabled(enum xfeature xfeature)
{
return !!(xfeatures_mask & (1UL << xfeature));
}
/*
* Record the offsets and sizes of various xstates contained
* in the XSAVE state memory layout.
*/
static void __init setup_xstate_features(void)
{
u32 eax, ebx, ecx, edx, i;
/* start at the beginnning of the "extended state" */
unsigned int last_good_offset = offsetof(struct xregs_state,
extended_state_area);
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
if (!xfeature_enabled(i))
continue;
cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
xstate_offsets[i] = ebx;
xstate_sizes[i] = eax;
/*
* In our xstate size checks, we assume that the
* highest-numbered xstate feature has the
* highest offset in the buffer. Ensure it does.
*/
WARN_ONCE(last_good_offset > xstate_offsets[i],
"x86/fpu: misordered xstate at %d\n", last_good_offset);
last_good_offset = xstate_offsets[i];
printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", i, ebx, i, eax);
}
}
static void __init 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%03Lx: '%s'\n", xstate_mask, feature_name);
}
/*
* Print out all the supported xstate features:
*/
static void __init print_xstate_features(void)
{
print_xstate_feature(XFEATURE_MASK_FP);
print_xstate_feature(XFEATURE_MASK_SSE);
print_xstate_feature(XFEATURE_MASK_YMM);
print_xstate_feature(XFEATURE_MASK_BNDREGS);
print_xstate_feature(XFEATURE_MASK_BNDCSR);
print_xstate_feature(XFEATURE_MASK_OPMASK);
print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
print_xstate_feature(XFEATURE_MASK_PKRU);
}
/*
* 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.
*/
static void __init 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 fxregs_state, xmm_space);
if (!boot_cpu_has(X86_FEATURE_XSAVES)) {
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
if (xfeature_enabled(i)) {
xstate_comp_offsets[i] = xstate_offsets[i];
xstate_comp_sizes[i] = xstate_sizes[i];
}
}
return;
}
xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
FXSAVE_SIZE + XSAVE_HDR_SIZE;
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
if (xfeature_enabled(i))
xstate_comp_sizes[i] = xstate_sizes[i];
else
xstate_comp_sizes[i] = 0;
if (i > FIRST_EXTENDED_XFEATURE)
xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
+ xstate_comp_sizes[i-1];
}
}
/*
* setup the xstate image representing the init state
*/
static void __init setup_init_fpu_buf(void)
{
static int on_boot_cpu __initdata = 1;
WARN_ON_FPU(!on_boot_cpu);
on_boot_cpu = 0;
if (!boot_cpu_has(X86_FEATURE_XSAVE))
return;
setup_xstate_features();
print_xstate_features();
if (boot_cpu_has(X86_FEATURE_XSAVES)) {
init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
init_fpstate.xsave.header.xfeatures = xfeatures_mask;
}
/*
* Init all the features state with header_bv being 0x0
*/
copy_kernel_to_xregs_booting(&init_fpstate.xsave);
/*
* Dump the init state again. This is to identify the init state
* of any feature which is not represented by all zero's.
*/
copy_xregs_to_kernel_booting(&init_fpstate.xsave);
}
static int xfeature_is_supervisor(int xfeature_nr)
{
/*
* We currently do not support supervisor states, but if
* we did, we could find out like this.
*
* SDM says: If state component i is a user state component,
* ECX[0] return 0; if state component i is a supervisor
* state component, ECX[0] returns 1.
u32 eax, ebx, ecx, edx;
cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;
return !!(ecx & 1);
*/
return 0;
}
/*
static int xfeature_is_user(int xfeature_nr)
{
return !xfeature_is_supervisor(xfeature_nr);
}
*/
/*
* This check is important because it is easy to get XSTATE_*
* confused with XSTATE_BIT_*.
*/
#define CHECK_XFEATURE(nr) do { \
WARN_ON(nr < FIRST_EXTENDED_XFEATURE); \
WARN_ON(nr >= XFEATURE_MAX); \
} while (0)
/*
* We could cache this like xstate_size[], but we only use
* it here, so it would be a waste of space.
*/
static int xfeature_is_aligned(int xfeature_nr)
{
u32 eax, ebx, ecx, edx;
CHECK_XFEATURE(xfeature_nr);
cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
/*
* The value returned by ECX[1] indicates the alignment
* of state component i when the compacted format
* of the extended region of an XSAVE area is used
*/
return !!(ecx & 2);
}
static int xfeature_uncompacted_offset(int xfeature_nr)
{
u32 eax, ebx, ecx, edx;
CHECK_XFEATURE(xfeature_nr);
cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
return ebx;
}
static int xfeature_size(int xfeature_nr)
{
u32 eax, ebx, ecx, edx;
CHECK_XFEATURE(xfeature_nr);
cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
return eax;
}
/*
* 'XSAVES' implies two different things:
* 1. saving of supervisor/system state
* 2. using the compacted format
*
* Use this function when dealing with the compacted format so
* that it is obvious which aspect of 'XSAVES' is being handled
* by the calling code.
*/
static int using_compacted_format(void)
{
return boot_cpu_has(X86_FEATURE_XSAVES);
}
static void __xstate_dump_leaves(void)
{
int i;
u32 eax, ebx, ecx, edx;
static int should_dump = 1;
if (!should_dump)
return;
should_dump = 0;
/*
* Dump out a few leaves past the ones that we support
* just in case there are some goodies up there
*/
for (i = 0; i < XFEATURE_MAX + 10; i++) {
cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
XSTATE_CPUID, i, eax, ebx, ecx, edx);
}
}
#define XSTATE_WARN_ON(x) do { \
if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) { \
__xstate_dump_leaves(); \
} \
} while (0)
#define XCHECK_SZ(sz, nr, nr_macro, __struct) do { \
if ((nr == nr_macro) && \
WARN_ONCE(sz != sizeof(__struct), \
"%s: struct is %zu bytes, cpu state %d bytes\n", \
__stringify(nr_macro), sizeof(__struct), sz)) { \
__xstate_dump_leaves(); \
} \
} while (0)
/*
* We have a C struct for each 'xstate'. We need to ensure
* that our software representation matches what the CPU
* tells us about the state's size.
*/
static void check_xstate_against_struct(int nr)
{
/*
* Ask the CPU for the size of the state.
*/
int sz = xfeature_size(nr);
/*
* Match each CPU state with the corresponding software
* structure.
*/
XCHECK_SZ(sz, nr, XFEATURE_YMM, struct ymmh_struct);
XCHECK_SZ(sz, nr, XFEATURE_BNDREGS, struct mpx_bndreg_state);
XCHECK_SZ(sz, nr, XFEATURE_BNDCSR, struct mpx_bndcsr_state);
XCHECK_SZ(sz, nr, XFEATURE_OPMASK, struct avx_512_opmask_state);
XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM, struct avx_512_hi16_state);
XCHECK_SZ(sz, nr, XFEATURE_PKRU, struct pkru_state);
/*
* Make *SURE* to add any feature numbers in below if
* there are "holes" in the xsave state component
* numbers.
*/
if ((nr < XFEATURE_YMM) ||
(nr >= XFEATURE_MAX) ||
(nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR)) {
WARN_ONCE(1, "no structure for xstate: %d\n", nr);
XSTATE_WARN_ON(1);
}
}
/*
* This essentially double-checks what the cpu told us about
* how large the XSAVE buffer needs to be. We are recalculating
* it to be safe.
*/
static void do_extra_xstate_size_checks(void)
{
int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
int i;
for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
if (!xfeature_enabled(i))
continue;
check_xstate_against_struct(i);
/*
* Supervisor state components can be managed only by
* XSAVES, which is compacted-format only.
*/
if (!using_compacted_format())
XSTATE_WARN_ON(xfeature_is_supervisor(i));
/* Align from the end of the previous feature */
if (xfeature_is_aligned(i))
paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
/*
* The offset of a given state in the non-compacted
* format is given to us in a CPUID leaf. We check
* them for being ordered (increasing offsets) in
* setup_xstate_features().
*/
if (!using_compacted_format())
paranoid_xstate_size = xfeature_uncompacted_offset(i);
/*
* The compacted-format offset always depends on where
* the previous state ended.
*/
paranoid_xstate_size += xfeature_size(i);
}
XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
}
/*
* Calculate total size of enabled xstates in XCR0/xfeatures_mask.
*
* Note the SDM's wording here. "sub-function 0" only enumerates
* the size of the *user* states. If we use it to size a buffer
* that we use 'XSAVES' on, we could potentially overflow the
* buffer because 'XSAVES' saves system states too.
*
* Note that we do not currently set any bits on IA32_XSS so
* 'XCR0 | IA32_XSS == XCR0' for now.
*/
static unsigned int __init calculate_xstate_size(void)
{
unsigned int eax, ebx, ecx, edx;
unsigned int calculated_xstate_size;
if (!boot_cpu_has(X86_FEATURE_XSAVES)) {
/*
* - CPUID function 0DH, sub-function 0:
* EBX enumerates the size (in bytes) required by
* the XSAVE instruction for an XSAVE area
* containing all the *user* state components
* corresponding to bits currently set in XCR0.
*/
cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
calculated_xstate_size = ebx;
} else {
/*
* - CPUID function 0DH, sub-function 1:
* EBX enumerates the size (in bytes) required by
* the XSAVES instruction for an XSAVE area
* containing all the state components
* corresponding to bits currently set in
* XCR0 | IA32_XSS.
*/
cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
calculated_xstate_size = ebx;
}
return calculated_xstate_size;
}
/*
* Will the runtime-enumerated 'xstate_size' fit in the init
* task's statically-allocated buffer?
*/
static bool is_supported_xstate_size(unsigned int test_xstate_size)
{
if (test_xstate_size <= sizeof(union fpregs_state))
return true;
pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
sizeof(union fpregs_state), test_xstate_size);
return false;
}
static int init_xstate_size(void)
{
/* Recompute the context size for enabled features: */
unsigned int possible_xstate_size = calculate_xstate_size();
/* Ensure we have the space to store all enabled: */
if (!is_supported_xstate_size(possible_xstate_size))
return -EINVAL;
/*
* The size is OK, we are definitely going to use xsave,
* make it known to the world that we need more space.
*/
xstate_size = possible_xstate_size;
do_extra_xstate_size_checks();
return 0;
}
/*
* We enabled the XSAVE hardware, but something went wrong and
* we can not use it. Disable it.
*/
static void fpu__init_disable_system_xstate(void)
{
xfeatures_mask = 0;
cr4_clear_bits(X86_CR4_OSXSAVE);
fpu__xstate_clear_all_cpu_caps();
}
/*
* Enable and initialize the xsave feature.
* Called once per system bootup.
*/
void __init fpu__init_system_xstate(void)
{
unsigned int eax, ebx, ecx, edx;
static int on_boot_cpu __initdata = 1;
int err;
WARN_ON_FPU(!on_boot_cpu);
on_boot_cpu = 0;
if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
pr_info("x86/fpu: Legacy x87 FPU detected.\n");
return;
}
if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
WARN_ON_FPU(1);
return;
}
cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
xfeatures_mask = eax + ((u64)edx << 32);
if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
BUG();
}
xfeatures_mask &= fpu__get_supported_xfeatures_mask();
/* Enable xstate instructions to be able to continue with initialization: */
fpu__init_cpu_xstate();
err = init_xstate_size();
if (err) {
/* something went wrong, boot without any XSAVE support */
fpu__init_disable_system_xstate();
return;
}
update_regset_xstate_info(xstate_size, xfeatures_mask);
fpu__init_prepare_fx_sw_frame();
setup_init_fpu_buf();
setup_xstate_comp();
pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
xfeatures_mask,
xstate_size,
boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
}
/*
* Restore minimal FPU state after suspend:
*/
void fpu__resume_cpu(void)
{
/*
* Restore XCR0 on xsave capable CPUs:
*/
if (boot_cpu_has(X86_FEATURE_XSAVE))
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}
/*
* Given an xstate feature mask, calculate where in the xsave
* buffer the state is. Callers should ensure that the buffer
* is valid.
*
* Note: does not work for compacted buffers.
*/
void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
{
int feature_nr = fls64(xstate_feature_mask) - 1;
return (void *)xsave + xstate_comp_offsets[feature_nr];
}
/*
* 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.
*
* Note that if there is no data for the field in the xsave buffer
* this will return NULL.
*
* Inputs:
* xstate: the thread's storage area for all FPU data
* xstate_feature: state which is defined in xsave.h (e.g.
* XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
* Output:
* address of the state in the xsave area, or NULL if the
* field is not present in the xsave buffer.
*/
void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
{
/*
* Do we even *have* xsave state?
*/
if (!boot_cpu_has(X86_FEATURE_XSAVE))
return NULL;
/*
* We should not ever be requesting features that we
* have not enabled. Remember that pcntxt_mask is
* what we write to the XCR0 register.
*/
WARN_ONCE(!(xfeatures_mask & xstate_feature),
"get of unsupported state");
/*
* This assumes the last 'xsave*' instruction to
* have requested that 'xstate_feature' be saved.
* If it did not, we might be seeing and old value
* of the field in the buffer.
*
* This can happen because the last 'xsave' did not
* request that this feature be saved (unlikely)
* or because the "init optimization" caused it
* to not be saved.
*/
if (!(xsave->header.xfeatures & xstate_feature))
return NULL;
return __raw_xsave_addr(xsave, xstate_feature);
}
EXPORT_SYMBOL_GPL(get_xsave_addr);
/*
* This wraps up the common operations that need to occur when retrieving
* data from xsave state. It first ensures that the current task was
* using the FPU and retrieves the data in to a buffer. It then calculates
* the offset of the requested field in the buffer.
*
* This function is safe to call whether the FPU is in use or not.
*
* Note that this only works on the current task.
*
* Inputs:
* @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
* XFEATURE_MASK_SSE, etc...)
* Output:
* address of the state in the xsave area or NULL if the state
* is not present or is in its 'init state'.
*/
const void *get_xsave_field_ptr(int xsave_state)
{
struct fpu *fpu = ¤t->thread.fpu;
if (!fpu->fpstate_active)
return NULL;
/*
* fpu__save() takes the CPU's xstate registers
* and saves them off to the 'fpu memory buffer.
*/
fpu__save(fpu);
return get_xsave_addr(&fpu->state.xsave, xsave_state);
}
/*
* Set xfeatures (aka XSTATE_BV) bit for a feature that we want
* to take out of its "init state". This will ensure that an
* XRSTOR actually restores the state.
*/
static void fpu__xfeature_set_non_init(struct xregs_state *xsave,
int xstate_feature_mask)
{
xsave->header.xfeatures |= xstate_feature_mask;
}
/*
* This function is safe to call whether the FPU is in use or not.
*
* Note that this only works on the current task.
*
* Inputs:
* @xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
* XFEATURE_MASK_SSE, etc...)
* @xsave_state_ptr: a pointer to a copy of the state that you would
* like written in to the current task's FPU xsave state. This pointer
* must not be located in the current tasks's xsave area.
* Output:
* address of the state in the xsave area or NULL if the state
* is not present or is in its 'init state'.
*/
static void fpu__xfeature_set_state(int xstate_feature_mask,
void *xstate_feature_src, size_t len)
{
struct xregs_state *xsave = ¤t->thread.fpu.state.xsave;
struct fpu *fpu = ¤t->thread.fpu;
void *dst;
if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
WARN_ONCE(1, "%s() attempted with no xsave support", __func__);
return;
}
/*
* Tell the FPU code that we need the FPU state to be in
* 'fpu' (not in the registers), and that we need it to
* be stable while we write to it.
*/
fpu__current_fpstate_write_begin();
/*
* This method *WILL* *NOT* work for compact-format
* buffers. If the 'xstate_feature_mask' is unset in
* xcomp_bv then we may need to move other feature state
* "up" in the buffer.
*/
if (xsave->header.xcomp_bv & xstate_feature_mask) {
WARN_ON_ONCE(1);
goto out;
}
/* find the location in the xsave buffer of the desired state */
dst = __raw_xsave_addr(&fpu->state.xsave, xstate_feature_mask);
/*
* Make sure that the pointer being passed in did not
* come from the xsave buffer itself.
*/
WARN_ONCE(xstate_feature_src == dst, "set from xsave buffer itself");
/* put the caller-provided data in the location */
memcpy(dst, xstate_feature_src, len);
/*
* Mark the xfeature so that the CPU knows there is state
* in the buffer now.
*/
fpu__xfeature_set_non_init(xsave, xstate_feature_mask);
out:
/*
* We are done writing to the 'fpu'. Reenable preeption
* and (possibly) move the fpstate back in to the fpregs.
*/
fpu__current_fpstate_write_end();
}
#define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2)
#define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1)
/*
* This will go out and modify the XSAVE buffer so that PKRU is
* set to a particular state for access to 'pkey'.
*
* PKRU state does affect kernel access to user memory. We do
* not modfiy PKRU *itself* here, only the XSAVE state that will
* be restored in to PKRU when we return back to userspace.
*/
int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
struct pkru_state *old_pkru_state;
struct pkru_state new_pkru_state;
int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
u32 new_pkru_bits = 0;
/*
* This check implies XSAVE support. OSPKE only gets
* set if we enable XSAVE and we enable PKU in XCR0.
*/
if (!boot_cpu_has(X86_FEATURE_OSPKE))
return -EINVAL;
/* Set the bits we need in PKRU */
if (init_val & PKEY_DISABLE_ACCESS)
new_pkru_bits |= PKRU_AD_BIT;
if (init_val & PKEY_DISABLE_WRITE)
new_pkru_bits |= PKRU_WD_BIT;
/* Shift the bits in to the correct place in PKRU for pkey. */
new_pkru_bits <<= pkey_shift;
/* Locate old copy of the state in the xsave buffer */
old_pkru_state = get_xsave_addr(xsave, XFEATURE_MASK_PKRU);
/*
* When state is not in the buffer, it is in the init
* state, set it manually. Otherwise, copy out the old
* state.
*/
if (!old_pkru_state)
new_pkru_state.pkru = 0;
else
new_pkru_state.pkru = old_pkru_state->pkru;
/* mask off any old bits in place */
new_pkru_state.pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);
/* Set the newly-requested bits */
new_pkru_state.pkru |= new_pkru_bits;
/*
* We could theoretically live without zeroing pkru.pad.
* The current XSAVE feature state definition says that
* only bytes 0->3 are used. But we do not want to
* chance leaking kernel stack out to userspace in case a
* memcpy() of the whole xsave buffer was done.
*
* They're in the same cacheline anyway.
*/
new_pkru_state.pad = 0;
fpu__xfeature_set_state(XFEATURE_MASK_PKRU, &new_pkru_state,
sizeof(new_pkru_state));
return 0;
}
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