![Ingo Molnar](/assets/img/avatar_default.png)
fix warning: arch/x86/kernel/xsave.c: In function ‘save_i387_xstate’: arch/x86/kernel/xsave.c:98: warning: ignoring return value of ‘__clear_user’, declared with attribute warn_unused_result check the return value and act on it. We should not be ignoring faults at this point. Signed-off-by: Ingo Molnar <mingo@elte.hu>
346 lines
8 KiB
C
346 lines
8 KiB
C
/*
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* xsave/xrstor support.
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*
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* Author: Suresh Siddha <suresh.b.siddha@intel.com>
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*/
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#include <linux/bootmem.h>
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#include <linux/compat.h>
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#include <asm/i387.h>
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#ifdef CONFIG_IA32_EMULATION
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#include <asm/sigcontext32.h>
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#endif
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#include <asm/xcr.h>
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/*
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* Supported feature mask by the CPU and the kernel.
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*/
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u64 pcntxt_mask;
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struct _fpx_sw_bytes fx_sw_reserved;
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#ifdef CONFIG_IA32_EMULATION
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struct _fpx_sw_bytes fx_sw_reserved_ia32;
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#endif
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/*
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* Check for the presence of extended state information in the
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* user fpstate pointer in the sigcontext.
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*/
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int check_for_xstate(struct i387_fxsave_struct __user *buf,
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void __user *fpstate,
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struct _fpx_sw_bytes *fx_sw_user)
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{
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int min_xstate_size = sizeof(struct i387_fxsave_struct) +
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sizeof(struct xsave_hdr_struct);
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unsigned int magic2;
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int err;
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err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
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sizeof(struct _fpx_sw_bytes));
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if (err)
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return err;
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/*
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* First Magic check failed.
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*/
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if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
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return -1;
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/*
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* Check for error scenarios.
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*/
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if (fx_sw_user->xstate_size < min_xstate_size ||
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fx_sw_user->xstate_size > xstate_size ||
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fx_sw_user->xstate_size > fx_sw_user->extended_size)
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return -1;
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err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
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fx_sw_user->extended_size -
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FP_XSTATE_MAGIC2_SIZE));
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/*
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* Check for the presence of second magic word at the end of memory
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* layout. This detects the case where the user just copied the legacy
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* fpstate layout with out copying the extended state information
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* in the memory layout.
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*/
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if (err || magic2 != FP_XSTATE_MAGIC2)
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return -1;
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return 0;
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}
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#ifdef CONFIG_X86_64
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/*
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* Signal frame handlers.
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*/
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int save_i387_xstate(void __user *buf)
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{
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struct task_struct *tsk = current;
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int err = 0;
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if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
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return -EACCES;
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BUG_ON(sig_xstate_size < xstate_size);
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if ((unsigned long)buf % 64)
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printk("save_i387_xstate: bad fpstate %p\n", buf);
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if (!used_math())
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return 0;
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clear_used_math(); /* trigger finit */
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if (task_thread_info(tsk)->status & TS_USEDFPU) {
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/*
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* Start with clearing the user buffer. This will present a
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* clean context for the bytes not touched by the fxsave/xsave.
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*/
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err = __clear_user(buf, sig_xstate_size);
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if (err)
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return err;
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if (task_thread_info(tsk)->status & TS_XSAVE)
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err = xsave_user(buf);
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else
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err = fxsave_user(buf);
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if (err)
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return err;
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task_thread_info(tsk)->status &= ~TS_USEDFPU;
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stts();
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} else {
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if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
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xstate_size))
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return -1;
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}
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if (task_thread_info(tsk)->status & TS_XSAVE) {
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struct _fpstate __user *fx = buf;
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struct _xstate __user *x = buf;
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u64 xstate_bv;
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err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
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sizeof(struct _fpx_sw_bytes));
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err |= __put_user(FP_XSTATE_MAGIC2,
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(__u32 __user *) (buf + sig_xstate_size
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- FP_XSTATE_MAGIC2_SIZE));
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/*
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* Read the xstate_bv which we copied (directly from the cpu or
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* from the state in task struct) to the user buffers and
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* set the FP/SSE bits.
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*/
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err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
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/*
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* For legacy compatible, we always set FP/SSE bits in the bit
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* vector while saving the state to the user context. This will
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* enable us capturing any changes(during sigreturn) to
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* the FP/SSE bits by the legacy applications which don't touch
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* xstate_bv in the xsave header.
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*
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* xsave aware apps can change the xstate_bv in the xsave
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* header as well as change any contents in the memory layout.
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* xrestore as part of sigreturn will capture all the changes.
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*/
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xstate_bv |= XSTATE_FPSSE;
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err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
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if (err)
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return err;
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}
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return 1;
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}
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/*
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* Restore the extended state if present. Otherwise, restore the FP/SSE
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* state.
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*/
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int restore_user_xstate(void __user *buf)
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{
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struct _fpx_sw_bytes fx_sw_user;
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u64 mask;
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int err;
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if (((unsigned long)buf % 64) ||
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check_for_xstate(buf, buf, &fx_sw_user))
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goto fx_only;
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mask = fx_sw_user.xstate_bv;
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/*
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* restore the state passed by the user.
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*/
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err = xrestore_user(buf, mask);
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if (err)
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return err;
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/*
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* init the state skipped by the user.
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*/
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mask = pcntxt_mask & ~mask;
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xrstor_state(init_xstate_buf, mask);
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return 0;
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fx_only:
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/*
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* couldn't find the extended state information in the
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* memory layout. Restore just the FP/SSE and init all
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* the other extended state.
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*/
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xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
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return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
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}
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/*
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* This restores directly out of user space. Exceptions are handled.
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*/
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int restore_i387_xstate(void __user *buf)
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{
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struct task_struct *tsk = current;
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int err = 0;
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if (!buf) {
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if (used_math())
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goto clear;
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return 0;
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} else
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if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
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return -EACCES;
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if (!used_math()) {
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err = init_fpu(tsk);
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if (err)
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return err;
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}
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if (!(task_thread_info(current)->status & TS_USEDFPU)) {
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clts();
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task_thread_info(current)->status |= TS_USEDFPU;
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}
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if (task_thread_info(tsk)->status & TS_XSAVE)
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err = restore_user_xstate(buf);
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else
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err = fxrstor_checking((__force struct i387_fxsave_struct *)
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buf);
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if (unlikely(err)) {
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/*
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* Encountered an error while doing the restore from the
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* user buffer, clear the fpu state.
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*/
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clear:
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clear_fpu(tsk);
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clear_used_math();
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}
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return err;
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}
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#endif
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/*
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* Prepare the SW reserved portion of the fxsave memory layout, indicating
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* the presence of the extended state information in the memory layout
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* pointed by the fpstate pointer in the sigcontext.
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* This will be saved when ever the FP and extended state context is
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* saved on the user stack during the signal handler delivery to the user.
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*/
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void prepare_fx_sw_frame(void)
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{
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int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
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FP_XSTATE_MAGIC2_SIZE;
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sig_xstate_size = sizeof(struct _fpstate) + size_extended;
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#ifdef CONFIG_IA32_EMULATION
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sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
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#endif
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memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
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fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
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fx_sw_reserved.extended_size = sig_xstate_size;
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fx_sw_reserved.xstate_bv = pcntxt_mask;
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fx_sw_reserved.xstate_size = xstate_size;
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#ifdef CONFIG_IA32_EMULATION
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memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
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sizeof(struct _fpx_sw_bytes));
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fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
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#endif
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}
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/*
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* Represents init state for the supported extended state.
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*/
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struct xsave_struct *init_xstate_buf;
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#ifdef CONFIG_X86_64
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unsigned int sig_xstate_size = sizeof(struct _fpstate);
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#endif
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/*
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* Enable the extended processor state save/restore feature
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*/
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void __cpuinit xsave_init(void)
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{
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if (!cpu_has_xsave)
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return;
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set_in_cr4(X86_CR4_OSXSAVE);
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/*
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* Enable all the features that the HW is capable of
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* and the Linux kernel is aware of.
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*/
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xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
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}
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/*
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* setup the xstate image representing the init state
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*/
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static void __init setup_xstate_init(void)
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{
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init_xstate_buf = alloc_bootmem(xstate_size);
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init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
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}
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/*
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* Enable and initialize the xsave feature.
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*/
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void __init xsave_cntxt_init(void)
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{
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unsigned int eax, ebx, ecx, edx;
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cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
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pcntxt_mask = eax + ((u64)edx << 32);
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if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
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printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
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pcntxt_mask);
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BUG();
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}
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/*
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* for now OS knows only about FP/SSE
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*/
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pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
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xsave_init();
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/*
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* Recompute the context size for enabled features
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*/
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cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
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xstate_size = ebx;
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prepare_fx_sw_frame();
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setup_xstate_init();
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printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
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"cntxt size 0x%x\n",
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pcntxt_mask, xstate_size);
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}
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