// SPDX-License-Identifier: GPL-2.0
/*
* FPU signal frame handling routines.
*/
#include <linux/compat.h>
#include <linux/cpu.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/regset.h>
#include <asm/fpu/xstate.h>
#include <asm/sigframe.h>
#include <asm/trace/fpu.h>
static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
/*
* Check for the presence of extended state information in the
* user fpstate pointer in the sigcontext.
*/
static inline int check_for_xstate(struct fxregs_state __user *buf,
void __user *fpstate,
struct _fpx_sw_bytes *fx_sw)
{
int min_xstate_size = sizeof(struct fxregs_state) +
sizeof(struct xstate_header);
unsigned int magic2;
if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
return -1;
/* Check for the first magic field and other error scenarios. */
if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
fx_sw->xstate_size < min_xstate_size ||
fx_sw->xstate_size > fpu_user_xstate_size ||
fx_sw->xstate_size > fx_sw->extended_size)
return -1;
/*
* 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 (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
|| magic2 != FP_XSTATE_MAGIC2)
return -1;
return 0;
}
/*
* Signal frame handlers.
*/
static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
{
if (use_fxsr()) {
struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
struct user_i387_ia32_struct env;
struct _fpstate_32 __user *fp = buf;
convert_from_fxsr(&env, tsk);
if (__copy_to_user(buf, &env, sizeof(env)) ||
__put_user(xsave->i387.swd, &fp->status) ||
__put_user(X86_FXSR_MAGIC, &fp->magic))
return -1;
} else {
struct fregs_state __user *fp = buf;
u32 swd;
if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
return -1;
}
return 0;
}
static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
{
struct xregs_state __user *x = buf;
struct _fpx_sw_bytes *sw_bytes;
u32 xfeatures;
int err;
/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
if (!use_xsave())
return err;
err |= __put_user(FP_XSTATE_MAGIC2,
(__u32 __user *)(buf + fpu_user_xstate_size));
/*
* Read the xfeatures which we copied (directly from the cpu or
* from the state in task struct) to the user buffers.
*/
err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
/*
* 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
* xfeatures in the xsave header.
*
* xsave aware apps can change the xfeatures in the xsave
* header as well as change any contents in the memory layout.
* xrestore as part of sigreturn will capture all the changes.
*/
xfeatures |= XFEATURE_MASK_FPSSE;
err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
return err;
}
static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
{
int err;
if (use_xsave())
err = copy_xregs_to_user(buf);
else if (use_fxsr())
err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
else
err = copy_fregs_to_user((struct fregs_state __user *) buf);
if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
err = -EFAULT;
return err;
}
/*
* Save the fpu, extended register state to the user signal frame.
*
* 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
* state is copied.
* 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
*
* buf == buf_fx for 64-bit frames and 32-bit fsave frame.
* buf != buf_fx for 32-bit frames with fxstate.
*
* Try to save it directly to the user frame with disabled page fault handler.
* If this fails then do the slow path where the FPU state is first saved to
* task's fpu->state and then copy it to the user frame pointed to by the
* aligned pointer 'buf_fx'.
*
* If this is a 32-bit frame with fxstate, put a fsave header before
* the aligned state at 'buf_fx'.
*
* For [f]xsave state, update the SW reserved fields in the [f]xsave frame
* indicating the absence/presence of the extended state to the user.
*/
int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
{
struct task_struct *tsk = current;
int ia32_fxstate = (buf != buf_fx);
int ret;
ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
IS_ENABLED(CONFIG_IA32_EMULATION));
if (!access_ok(buf, size))
return -EACCES;
if (!static_cpu_has(X86_FEATURE_FPU))
return fpregs_soft_get(current, NULL, 0,
sizeof(struct user_i387_ia32_struct), NULL,
(struct _fpstate_32 __user *) buf) ? -1 : 1;
retry:
/*
* Load the FPU registers if they are not valid for the current task.
* With a valid FPU state we can attempt to save the state directly to
* userland's stack frame which will likely succeed. If it does not,
* resolve the fault in the user memory and try again.
*/
fpregs_lock();
if (test_thread_flag(TIF_NEED_FPU_LOAD))
__fpregs_load_activate();
pagefault_disable();
ret = copy_fpregs_to_sigframe(buf_fx);
pagefault_enable();
fpregs_unlock();
if (ret) {
int aligned_size;
int nr_pages;
aligned_size = offset_in_page(buf_fx) + fpu_user_xstate_size;
nr_pages = DIV_ROUND_UP(aligned_size, PAGE_SIZE);
ret = get_user_pages_unlocked((unsigned long)buf_fx, nr_pages,
NULL, FOLL_WRITE);
if (ret == nr_pages)
goto retry;
return -EFAULT;
}
/* Save the fsave header for the 32-bit frames. */
if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
return -1;
if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
return -1;
return 0;
}
static inline void
sanitize_restored_xstate(union fpregs_state *state,
struct user_i387_ia32_struct *ia32_env,
u64 xfeatures, int fx_only)
{
struct xregs_state *xsave = &state->xsave;
struct xstate_header *header = &xsave->header;
if (use_xsave()) {
/*
* Note: we don't need to zero the reserved bits in the
* xstate_header here because we either didn't copy them at all,
* or we checked earlier that they aren't set.
*/
/*
* Init the state that is not present in the memory
* layout and not enabled by the OS.
*/
if (fx_only)
header->xfeatures = XFEATURE_MASK_FPSSE;
else
header->xfeatures &= xfeatures;
}
if (use_fxsr()) {
/*
* mscsr reserved bits must be masked to zero for security
* reasons.
*/
xsave->i387.mxcsr &= mxcsr_feature_mask;
if (ia32_env)
convert_to_fxsr(&state->fxsave, ia32_env);
}
}
/*
* Restore the extended state if present. Otherwise, restore the FP/SSE state.
*/
static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
{
if (use_xsave()) {
if (fx_only) {
u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
return copy_user_to_fxregs(buf);
} else {
u64 init_bv = xfeatures_mask & ~xbv;
if (unlikely(init_bv))
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
return copy_user_to_xregs(buf, xbv);
}
} else if (use_fxsr()) {
return copy_user_to_fxregs(buf);
} else
return copy_user_to_fregs(buf);
}
static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
{
struct user_i387_ia32_struct *envp = NULL;
int state_size = fpu_kernel_xstate_size;
int ia32_fxstate = (buf != buf_fx);
struct task_struct *tsk = current;
struct fpu *fpu = &tsk->thread.fpu;
struct user_i387_ia32_struct env;
u64 xfeatures = 0;
int fx_only = 0;
int ret = 0;
ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
IS_ENABLED(CONFIG_IA32_EMULATION));
if (!buf) {
fpu__clear(fpu);
return 0;
}
if (!access_ok(buf, size))
return -EACCES;
if (!static_cpu_has(X86_FEATURE_FPU))
return fpregs_soft_set(current, NULL,
0, sizeof(struct user_i387_ia32_struct),
NULL, buf) != 0;
if (use_xsave()) {
struct _fpx_sw_bytes fx_sw_user;
if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
/*
* Couldn't find the extended state information in the
* memory layout. Restore just the FP/SSE and init all
* the other extended state.
*/
state_size = sizeof(struct fxregs_state);
fx_only = 1;
trace_x86_fpu_xstate_check_failed(fpu);
} else {
state_size = fx_sw_user.xstate_size;
xfeatures = fx_sw_user.xfeatures;
}
}
/*
* The current state of the FPU registers does not matter. By setting
* TIF_NEED_FPU_LOAD unconditionally it is ensured that the our xstate
* is not modified on context switch and that the xstate is considered
* to be loaded again on return to userland (overriding last_cpu avoids
* the optimisation).
*/
set_thread_flag(TIF_NEED_FPU_LOAD);
__fpu_invalidate_fpregs_state(fpu);
if ((unsigned long)buf_fx % 64)
fx_only = 1;
/*
* For 32-bit frames with fxstate, copy the fxstate so it can be
* reconstructed later.
*/
if (ia32_fxstate) {
ret = __copy_from_user(&env, buf, sizeof(env));
if (ret)
goto err_out;
envp = &env;
} else {
/*
* Attempt to restore the FPU registers directly from user
* memory. For that to succeed, the user access cannot cause
* page faults. If it does, fall back to the slow path below,
* going through the kernel buffer with the enabled pagefault
* handler.
*/
fpregs_lock();
pagefault_disable();
ret = copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only);
pagefault_enable();
if (!ret) {
fpregs_mark_activate();
fpregs_unlock();
return 0;
}
fpregs_unlock();
}
if (use_xsave() && !fx_only) {
u64 init_bv = xfeatures_mask & ~xfeatures;
if (using_compacted_format()) {
ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
} else {
ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
if (!ret && state_size > offsetof(struct xregs_state, header))
ret = validate_xstate_header(&fpu->state.xsave.header);
}
if (ret)
goto err_out;
sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
fpregs_lock();
if (unlikely(init_bv))
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
ret = copy_kernel_to_xregs_err(&fpu->state.xsave, xfeatures);
} else if (use_fxsr()) {
ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
if (ret) {
ret = -EFAULT;
goto err_out;
}
sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
fpregs_lock();
if (use_xsave()) {
u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
}
ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
} else {
ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
if (ret)
goto err_out;
fpregs_lock();
ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
}
if (!ret)
fpregs_mark_activate();
fpregs_unlock();
err_out:
if (ret)
fpu__clear(fpu);
return ret;
}
static inline int xstate_sigframe_size(void)
{
return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
fpu_user_xstate_size;
}
/*
* Restore FPU state from a sigframe:
*/
int fpu__restore_sig(void __user *buf, int ia32_frame)
{
void __user *buf_fx = buf;
int size = xstate_sigframe_size();
if (ia32_frame && use_fxsr()) {
buf_fx = buf + sizeof(struct fregs_state);
size += sizeof(struct fregs_state);
}
return __fpu__restore_sig(buf, buf_fx, size);
}
unsigned long
fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
unsigned long *buf_fx, unsigned long *size)
{
unsigned long frame_size = xstate_sigframe_size();
*buf_fx = sp = round_down(sp - frame_size, 64);
if (ia32_frame && use_fxsr()) {
frame_size += sizeof(struct fregs_state);
sp -= sizeof(struct fregs_state);
}
*size = frame_size;
return sp;
}
/*
* 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 fpu__init_prepare_fx_sw_frame(void)
{
int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
fx_sw_reserved.extended_size = size;
fx_sw_reserved.xfeatures = xfeatures_mask;
fx_sw_reserved.xstate_size = fpu_user_xstate_size;
if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
IS_ENABLED(CONFIG_X86_32)) {
int fsave_header_size = sizeof(struct fregs_state);
fx_sw_reserved_ia32 = fx_sw_reserved;
fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
}
}
