path: root/arch/x86/kernel/fpu/xstate.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * xsave/xrstor support.
 *
 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
 */
#include <linux/compat.h>
#include <linux/cpu.h>
#include <linux/mman.h>
#include <linux/pkeys.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.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>

#include "xstate.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",
	"PASID state",
	"unknown xstate feature"	,
};

static short xsave_cpuid_features[] __initdata = {
	X86_FEATURE_FPU,
	X86_FEATURE_XMM,
	X86_FEATURE_AVX,
	X86_FEATURE_MPX,
	X86_FEATURE_MPX,
	X86_FEATURE_AVX512F,
	X86_FEATURE_AVX512F,
	X86_FEATURE_AVX512F,
	X86_FEATURE_INTEL_PT,
	X86_FEATURE_PKU,
	X86_FEATURE_ENQCMD,
};

/*
 * This represents the full set of bits that should ever be set in a kernel
 * XSAVE buffer, both supervisor and user xstates.
 */
u64 xfeatures_mask_all __ro_after_init;
EXPORT_SYMBOL_GPL(xfeatures_mask_all);

static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
	{ [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_sizes[XFEATURE_MAX] __ro_after_init =
	{ [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_comp_offsets[XFEATURE_MAX] __ro_after_init =
	{ [ 0 ... XFEATURE_MAX - 1] = -1};
static unsigned int xstate_supervisor_only_offsets[XFEATURE_MAX] __ro_after_init =
	{ [ 0 ... XFEATURE_MAX - 1] = -1};

/*
 * The XSAVE area of kernel can be in standard or compacted format;
 * it is always in standard format for user mode. This is the user
 * mode standard format size used for signal and ptrace frames.
 */
unsigned int fpu_user_xstate_size __ro_after_init;

/*
 * 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_all;

	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);

static bool xfeature_is_supervisor(int xfeature_nr)
{
	/*
	 * Extended State Enumeration Sub-leaves (EAX = 0DH, ECX = n, n > 1)
	 * returns ECX[0] set to (1) for a supervisor state, and cleared (0)
	 * for a user state.
	 */
	u32 eax, ebx, ecx, edx;

	cpuid_count(XSTATE_CPUID