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-rw-r--r--arch/x86/kernel/fpu/signal.c540
1 files changed, 540 insertions, 0 deletions
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
new file mode 100644
index 000000000..b7b92cdf3
--- /dev/null
+++ b/arch/x86/kernel/fpu/signal.c
@@ -0,0 +1,540 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * FPU signal frame handling routines.
+ */
+
+#include <linux/compat.h>
+#include <linux/cpu.h>
+#include <linux/pagemap.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;
+
+ fpregs_lock();
+ if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+ copy_fxregs_to_kernel(&tsk->thread.fpu);
+ fpregs_unlock();
+
+ 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 (!static_cpu_has(X86_FEATURE_FPU)) {
+ struct user_i387_ia32_struct fp;
+ fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
+ .left = sizeof(fp)});
+ return copy_to_user(buf, &fp, sizeof(fp)) ? -EFAULT : 0;
+ }
+
+ if (!access_ok(buf, size))
+ return -EACCES;
+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) {
+ if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
+ 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_user_xstate(union fpregs_state *state,
+ struct user_i387_ia32_struct *ia32_env,
+ u64 user_xfeatures, int fx_only)
+{
+ struct xregs_state *xsave = &state->xsave;
+ struct xstate_header *header = &xsave->header;
+
+ if (use_xsave()) {
+ /*
+ * Clear all feature bits which are not set in
+ * user_xfeatures and clear all extended features
+ * for fx_only mode.
+ */
+ u64 mask = fx_only ? XFEATURE_MASK_FPSSE : user_xfeatures;
+
+ /*
+ * Supervisor state has to be preserved. The sigframe
+ * restore can only modify user features, i.e. @mask
+ * cannot contain them.
+ */
+ header->xfeatures &= mask | xfeatures_mask_supervisor();
+ }
+
+ 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)
+{
+ u64 init_bv;
+ int r;
+
+ if (use_xsave()) {
+ if (fx_only) {
+ init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
+
+ r = copy_user_to_fxregs(buf);
+ if (!r)
+ copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+ return r;
+ } else {
+ init_bv = xfeatures_mask_user() & ~xbv;
+
+ r = copy_user_to_xregs(buf, xbv);
+ if (!r && unlikely(init_bv))
+ copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+ return r;
+ }
+ } 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 user_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_user_states(fpu);
+ return 0;
+ }
+
+ if (!access_ok(buf, size)) {
+ ret = -EACCES;
+ goto out;
+ }
+
+ if (!static_cpu_has(X86_FEATURE_FPU)) {
+ ret = fpregs_soft_set(current, NULL, 0,
+ sizeof(struct user_i387_ia32_struct),
+ NULL, buf);
+ goto out;
+ }
+
+ 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;
+ user_xfeatures = fx_sw_user.xfeatures;
+ }
+ }
+
+ if ((unsigned long)buf_fx % 64)
+ fx_only = 1;
+
+ if (!ia32_fxstate) {
+ /*
+ * 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, user_xfeatures, fx_only);
+ pagefault_enable();
+ if (!ret) {
+
+ /*
+ * Restore supervisor states: previous context switch
+ * etc has done XSAVES and saved the supervisor states
+ * in the kernel buffer from which they can be restored
+ * now.
+ *
+ * We cannot do a single XRSTORS here - which would
+ * be nice - because the rest of the FPU registers are
+ * being restored from a user buffer directly. The
+ * single XRSTORS happens below, when the user buffer
+ * has been copied to the kernel one.
+ */
+ if (test_thread_flag(TIF_NEED_FPU_LOAD) &&
+ xfeatures_mask_supervisor())
+ copy_kernel_to_xregs(&fpu->state.xsave,
+ xfeatures_mask_supervisor());
+ fpregs_mark_activate();
+ fpregs_unlock();
+ return 0;
+ }
+
+ /*
+ * The above did an FPU restore operation, restricted to
+ * the user portion of the registers, and failed, but the
+ * microcode might have modified the FPU registers
+ * nevertheless.
+ *
+ * If the FPU registers do not belong to current, then
+ * invalidate the FPU register state otherwise the task might
+ * preempt current and return to user space with corrupted
+ * FPU registers.
+ *
+ * In case current owns the FPU registers then no further
+ * action is required. The fixup below will handle it
+ * correctly.
+ */
+ if (test_thread_flag(TIF_NEED_FPU_LOAD))
+ __cpu_invalidate_fpregs_state();
+
+ fpregs_unlock();
+ } else {
+ /*
+ * For 32-bit frames with fxstate, copy the fxstate so it can
+ * be reconstructed later.
+ */
+ ret = __copy_from_user(&env, buf, sizeof(env));
+ if (ret)
+ goto out;
+ envp = &env;
+ }
+
+ /*
+ * By setting TIF_NEED_FPU_LOAD it is ensured that 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).
+ */
+ fpregs_lock();
+
+ if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
+
+ /*
+ * Supervisor states are not modified by user space input. Save
+ * current supervisor states first and invalidate the FPU regs.
+ */
+ if (xfeatures_mask_supervisor())
+ copy_supervisor_to_kernel(&fpu->state.xsave);
+ set_thread_flag(TIF_NEED_FPU_LOAD);
+ }
+ __fpu_invalidate_fpregs_state(fpu);
+ fpregs_unlock();
+
+ if (use_xsave() && !fx_only) {
+ u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
+
+ ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
+ if (ret)
+ goto out;
+
+ sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
+ fx_only);
+
+ fpregs_lock();
+ if (unlikely(init_bv))
+ copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+
+ /*
+ * Restore previously saved supervisor xstates along with
+ * copied-in user xstates.
+ */
+ ret = copy_kernel_to_xregs_err(&fpu->state.xsave,
+ user_xfeatures | xfeatures_mask_supervisor());
+
+ } else if (use_fxsr()) {
+ ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
+ if (ret) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
+ fx_only);
+
+ fpregs_lock();
+ if (use_xsave()) {
+ u64 init_bv;
+
+ init_bv = xfeatures_mask_user() & ~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 out;
+
+ fpregs_lock();
+ ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
+ }
+ if (!ret)
+ fpregs_mark_activate();
+ else
+ fpregs_deactivate(fpu);
+ fpregs_unlock();
+
+out:
+ if (ret)
+ fpu__clear_user_states(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_user();
+ 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;
+ }
+}
+
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