swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Tip revision: f443e374ae131c168a065ea1748feac6b2e76613 authored by Linus Torvalds on 20 March 2022, 20:14:17 UTC
Linux 5.17
Linux 5.17
Tip revision: f443e37
regset.c
// SPDX-License-Identifier: GPL-2.0
/*
* FPU register's regset abstraction, for ptrace, core dumps, etc.
*/
#include <linux/sched/task_stack.h>
#include <linux/vmalloc.h>
#include <asm/fpu/api.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/regset.h>
#include "context.h"
#include "internal.h"
#include "legacy.h"
#include "xstate.h"
/*
* The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
* as the "regset->n" for the xstate regset will be updated based on the feature
* capabilities supported by the xsave.
*/
int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
return regset->n;
}
int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
if (boot_cpu_has(X86_FEATURE_FXSR))
return regset->n;
else
return 0;
}
/*
* The regset get() functions are invoked from:
*
* - coredump to dump the current task's fpstate. If the current task
* owns the FPU then the memory state has to be synchronized and the
* FPU register state preserved. Otherwise fpstate is already in sync.
*
* - ptrace to dump fpstate of a stopped task, in which case the registers
* have already been saved to fpstate on context switch.
*/
static void sync_fpstate(struct fpu *fpu)
{
if (fpu == ¤t->thread.fpu)
fpu_sync_fpstate(fpu);
}
/*
* Invalidate cached FPU registers before modifying the stopped target
* task's fpstate.
*
* This forces the target task on resume to restore the FPU registers from
* modified fpstate. Otherwise the task might skip the restore and operate
* with the cached FPU registers which discards the modifications.
*/
static void fpu_force_restore(struct fpu *fpu)
{
/*
* Only stopped child tasks can be used to modify the FPU
* state in the fpstate buffer:
*/
WARN_ON_FPU(fpu == ¤t->thread.fpu);
__fpu_invalidate_fpregs_state(fpu);
}
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
struct fpu *fpu = &target->thread.fpu;
if (!cpu_feature_enabled(X86_FEATURE_FXSR))
return -ENODEV;
sync_fpstate(fpu);
if (!use_xsave()) {
return membuf_write(&to, &fpu->fpstate->regs.fxsave,
sizeof(fpu->fpstate->regs.fxsave));
}
copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_FX);
return 0;
}
int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
struct fpu *fpu = &target->thread.fpu;
struct fxregs_state newstate;
int ret;
if (!cpu_feature_enabled(X86_FEATURE_FXSR))
return -ENODEV;
/* No funny business with partial or oversized writes is permitted. */
if (pos != 0 || count != sizeof(newstate))
return -EINVAL;
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1);
if (ret)
return ret;
/* Do not allow an invalid MXCSR value. */
if (newstate.mxcsr & ~mxcsr_feature_mask)
return -EINVAL;
fpu_force_restore(fpu);
/* Copy the state */
memcpy(&fpu->fpstate->regs.fxsave, &newstate, sizeof(newstate));
/* Clear xmm8..15 for 32-bit callers */
BUILD_BUG_ON(sizeof(fpu->__fpstate.regs.fxsave.xmm_space) != 16 * 16);
if (in_ia32_syscall())
memset(&fpu->fpstate->regs.fxsave.xmm_space[8*4], 0, 8 * 16);
/* Mark FP and SSE as in use when XSAVE is enabled */
if (use_xsave())
fpu->fpstate->regs.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
return 0;
}
int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
if (!cpu_feature_enabled(X86_FEATURE_XSAVE))
return -ENODEV;
sync_fpstate(&target->thread.fpu);
copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_XSAVE);
return 0;
}
int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
struct fpu *fpu = &target->thread.fpu;
struct xregs_state *tmpbuf = NULL;
int ret;
if (!cpu_feature_enabled(X86_FEATURE_XSAVE))
return -ENODEV;
/*
* A whole standard-format XSAVE buffer is needed:
*/
if (pos != 0 || count != fpu_user_cfg.max_size)
return -EFAULT;
if (!kbuf) {
tmpbuf = vmalloc(count);
if (!tmpbuf)
return -ENOMEM;
if (copy_from_user(tmpbuf, ubuf, count)) {
ret = -EFAULT;
goto out;
}
}
fpu_force_restore(fpu);
ret = copy_uabi_from_kernel_to_xstate(fpu->fpstate, kbuf ?: tmpbuf);
out:
vfree(tmpbuf);
return ret;
}
#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
/*
* FPU tag word conversions.
*/
static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
{
unsigned int tmp; /* to avoid 16 bit prefixes in the code */
/* Transform each pair of bits into 01 (valid) or 00 (empty) */
tmp = ~twd;
tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
/* and move the valid bits to the lower byte. */
tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
return tmp;
}
#define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16)
#define FP_EXP_TAG_VALID 0
#define FP_EXP_TAG_ZERO 1
#define FP_EXP_TAG_SPECIAL 2
#define FP_EXP_TAG_EMPTY 3
static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave)
{
struct _fpxreg *st;
u32 tos = (fxsave->swd >> 11) & 7;
u32 twd = (unsigned long) fxsave->twd;
u32 tag;
u32 ret = 0xffff0000u;
int i;
for (i = 0; i < 8; i++, twd >>= 1) {
if (twd & 0x1) {
st = FPREG_ADDR(fxsave, (i - tos) & 7);
switch (st->exponent & 0x7fff) {
case 0x7fff:
tag = FP_EXP_TAG_SPECIAL;
break;
case 0x0000:
if (!st->significand[0] &&
!st->significand[1] &&
!st->significand[2] &&
!st->significand[3])
tag = FP_EXP_TAG_ZERO;
else
tag = FP_EXP_TAG_SPECIAL;
break;
default:
if (st->significand[3] & 0x8000)
tag = FP_EXP_TAG_VALID;
else
tag = FP_EXP_TAG_SPECIAL;
break;
}
} else {
tag = FP_EXP_TAG_EMPTY;
}
ret |= tag << (2 * i);
}
return ret;
}
/*
* FXSR floating point environment conversions.
*/
static void __convert_from_fxsr(struct user_i387_ia32_struct *env,
struct task_struct *tsk,
struct fxregs_state *fxsave)
{
struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
int i;
env->cwd = fxsave->cwd | 0xffff0000u;
env->swd = fxsave->swd | 0xffff0000u;
env->twd = twd_fxsr_to_i387(fxsave);
#ifdef CONFIG_X86_64
env->fip = fxsave->rip;
env->foo = fxsave->rdp;
/*
* should be actually ds/cs at fpu exception time, but
* that information is not available in 64bit mode.
*/
env->fcs = task_pt_regs(tsk)->cs;
if (tsk == current) {
savesegment(ds, env->fos);
} else {
env->fos = tsk->thread.ds;
}
env->fos |= 0xffff0000;
#else
env->fip = fxsave->fip;
env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
env->foo = fxsave->foo;
env->fos = fxsave->fos;
#endif
for (i = 0; i < 8; ++i)
memcpy(&to[i], &from[i], sizeof(to[0]));
}
void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
__convert_from_fxsr(env, tsk, &tsk->thread.fpu.fpstate->regs.fxsave);
}
void convert_to_fxsr(struct fxregs_state *fxsave,
const struct user_i387_ia32_struct *env)
{
struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
int i;
fxsave->cwd = env->cwd;
fxsave->swd = env->swd;
fxsave->twd = twd_i387_to_fxsr(env->twd);
fxsave->fop = (u16) ((u32) env->fcs >> 16);
#ifdef CONFIG_X86_64
fxsave->rip = env->fip;
fxsave->rdp = env->foo;
/* cs and ds ignored */
#else
fxsave->fip = env->fip;
fxsave->fcs = (env->fcs & 0xffff);
fxsave->foo = env->foo;
fxsave->fos = env->fos;
#endif
for (i = 0; i < 8; ++i)
memcpy(&to[i], &from[i], sizeof(from[0]));
}
int fpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
struct fpu *fpu = &target->thread.fpu;
struct user_i387_ia32_struct env;
struct fxregs_state fxsave, *fx;
sync_fpstate(fpu);
if (!cpu_feature_enabled(X86_FEATURE_FPU))
return fpregs_soft_get(target, regset, to);
if (!cpu_feature_enabled(X86_FEATURE_FXSR)) {
return membuf_write(&to, &fpu->fpstate->regs.fsave,
sizeof(struct fregs_state));
}
if (use_xsave()) {
struct membuf mb = { .p = &fxsave, .left = sizeof(fxsave) };
/* Handle init state optimized xstate correctly */
copy_xstate_to_uabi_buf(mb, target, XSTATE_COPY_FP);
fx = &fxsave;
} else {
fx = &fpu->fpstate->regs.fxsave;
}
__convert_from_fxsr(&env, target, fx);
return membuf_write(&to, &env, sizeof(env));
}
int fpregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
struct fpu *fpu = &target->thread.fpu;
struct user_i387_ia32_struct env;
int ret;
/* No funny business with partial or oversized writes is permitted. */
if (pos != 0 || count != sizeof(struct user_i387_ia32_struct))
return -EINVAL;
if (!cpu_feature_enabled(X86_FEATURE_FPU))
return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
if (ret)
return ret;
fpu_force_restore(fpu);
if (cpu_feature_enabled(X86_FEATURE_FXSR))
convert_to_fxsr(&fpu->fpstate->regs.fxsave, &env);
else
memcpy(&fpu->fpstate->regs.fsave, &env, sizeof(env));
/*
* Update the header bit in the xsave header, indicating the
* presence of FP.
*/
if (cpu_feature_enabled(X86_FEATURE_XSAVE))
fpu->fpstate->regs.xsave.header.xfeatures |= XFEATURE_MASK_FP;
return 0;
}
#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */