ARM: mmp: fix potential NULL dereference

[linux/fpc-iii.git] / arch / x86 / kernel / xsave.c

/*
 * xsave/xrstor support.
 *
 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bootmem.h>
#include <linux/compat.h>
#include <asm/i387.h>
#include <asm/fpu-internal.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;

/*
 * 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 *) (((void *)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 (err)
                        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();
}