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x86, xsave: save/restore the extended state context in sigframe

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On cpu's supporting xsave/xrstor, fpstate pointer in the sigcontext, will
include the extended state information along with fpstate information. Presence
of extended state information is indicated by the presence
of FP_XSTATE_MAGIC1 at fpstate.sw_reserved.magic1 and FP_XSTATE_MAGIC2
at fpstate + (fpstate.sw_reserved.extended_size - FP_XSTATE_MAGIC2_SIZE).

Extended feature bit mask that is saved in the memory layout is represented
by the fpstate.sw_reserved.xstate_bv

For RT signal frames, UC_FP_XSTATE in the uc_flags also indicate the
presence of extended state information in the sigcontext's fpstate
pointer.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Suresh Siddha
2008-07-29 10:29:25 -07:00
committed by Ingo Molnar
parent bdd8caba5e
commit c37b5efea4
8 changed files with 264 additions and 22 deletions
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172
arch/x86/kernel/xsave.c
View File

@@ -6,12 +6,68 @@
#include <linux/bootmem.h>
#include <linux/compat.h>
#include <asm/i387.h>
#ifdef CONFIG_IA32_EMULATION
#include <asm/sigcontext32.h>
#endif
/*
* Supported feature mask by the CPU and the kernel.
*/
unsigned int pcntxt_hmask, pcntxt_lmask;
struct _fpx_sw_bytes fx_sw_reserved;
#ifdef CONFIG_IA32_EMULATION
struct _fpx_sw_bytes fx_sw_reserved_ia32;
#endif
/*
* 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 err;
/*
* First Magic check failed.
*/
if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
return -1;
/*
* 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 -1;
err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
fx_sw_user->extended_size -
FP_XSTATE_MAGIC2_SIZE));
/*
* 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 (err || magic2 != FP_XSTATE_MAGIC2)
return -1;
return 0;
}
#ifdef CONFIG_X86_64
/*
* Signal frame handlers.
@@ -28,15 +84,18 @@ int save_i387_xstate(void __user *buf)
BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
sizeof(tsk->thread.xstate->fxsave));
if ((unsigned long)buf % 16)
if ((unsigned long)buf % 64)
printk("save_i387_xstate: bad fpstate %p\n", buf);
if (!used_math())
return 0;
clear_used_math(); /* trigger finit */
if (task_thread_info(tsk)->status & TS_USEDFPU) {
err = save_i387_checking((struct i387_fxsave_struct __user *)
buf);
if (task_thread_info(tsk)->status & TS_XSAVE)
err = xsave_user(buf);
else
err = fxsave_user(buf);
if (err)
return err;
task_thread_info(tsk)->status &= ~TS_USEDFPU;
@@ -46,23 +105,77 @@ int save_i387_xstate(void __user *buf)
xstate_size))
return -1;
}
if (task_thread_info(tsk)->status & TS_XSAVE) {
struct _fpstate __user *fx = buf;
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));
}
return 1;
}
/*
* Restore the extended state if present. Otherwise, restore the FP/SSE
* state.
*/
int restore_user_xstate(void __user *buf)
{
struct _fpx_sw_bytes fx_sw_user;
unsigned int lmask, hmask;
int err;
if (((unsigned long)buf % 64) ||
check_for_xstate(buf, buf, &fx_sw_user))
goto fx_only;
lmask = fx_sw_user.xstate_bv;
hmask = fx_sw_user.xstate_bv >> 32;
/*
* restore the state passed by the user.
*/
err = xrestore_user(buf, lmask, hmask);
if (err)
return err;
/*
* init the state skipped by the user.
*/
lmask = pcntxt_lmask & ~lmask;
hmask = pcntxt_hmask & ~hmask;
xrstor_state(init_xstate_buf, lmask, hmask);
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_lmask & ~XSTATE_FPSSE,
pcntxt_hmask);
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;
int err = 0;
if (!buf) {
if (used_math()) {
clear_fpu(tsk);
clear_used_math();
}
if (used_math())
goto clear;
return 0;
} else
if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
@@ -78,12 +191,17 @@ int restore_i387_xstate(void __user *buf)
clts();
task_thread_info(current)->status |= TS_USEDFPU;
}
err = fxrstor_checking((__force struct i387_fxsave_struct *)buf);
if (task_thread_info(tsk)->status & TS_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();
}
@@ -91,6 +209,38 @@ int restore_i387_xstate(void __user *buf)
}
#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.
*/
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_lmask |
(((u64) (pcntxt_hmask)) << 32);
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
}
/*
* Represents init state for the supported extended state.
*/
@@ -162,6 +312,8 @@ void __init xsave_cntxt_init(void)
xstate_size = ebx;
prepare_fx_sw_frame();
setup_xstate_init();
printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%Lx, "