The following commit has been merged into the x86/fpu branch of tip: Commit-ID: b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94 Gitweb: https://git.kernel.org/tip/b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94 Author: Fenghua Yu <[email protected]> AuthorDate: Tue, 12 May 2020 07:54:39 -07:00 Committer: Borislav Petkov <[email protected]> CommitterDate: Wed, 13 May 2020 13:41:50 +02:00
x86/fpu/xstate: Define new functions for clearing fpregs and xstates Currently, fpu__clear() clears all fpregs and xstates. Once XSAVES supervisor states are introduced, supervisor settings (e.g. CET xstates) must remain active for signals; It is necessary to have separate functions: - Create fpu__clear_user_states(): clear only user settings for signals; - Create fpu__clear_all(): clear both user and supervisor settings in flush_thread(). Also modify copy_init_fpstate_to_fpregs() to take a mask from above two functions. Remove obvious side-comment in fpu__clear(), while at it. [ bp: Make the second argument of fpu__clear() bool after requesting it a bunch of times during review. - Add a comment about copy_init_fpstate_to_fpregs() locking needs. ] Co-developed-by: Yu-cheng Yu <[email protected]> Signed-off-by: Fenghua Yu <[email protected]> Signed-off-by: Yu-cheng Yu <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Reviewed-by: Dave Hansen <[email protected]> Reviewed-by: Tony Luck <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- arch/x86/include/asm/fpu/internal.h | 3 +- arch/x86/kernel/fpu/core.c | 53 ++++++++++++++++++---------- arch/x86/kernel/fpu/signal.c | 4 +- arch/x86/kernel/process.c | 2 +- arch/x86/kernel/signal.c | 2 +- 5 files changed, 41 insertions(+), 23 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index ccb1bb3..a42fcb4 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -31,7 +31,8 @@ extern void fpu__save(struct fpu *fpu); extern int fpu__restore_sig(void __user *buf, int ia32_frame); extern void fpu__drop(struct fpu *fpu); extern int fpu__copy(struct task_struct *dst, struct task_struct *src); -extern void fpu__clear(struct fpu *fpu); +extern void fpu__clear_user_states(struct fpu *fpu); +extern void fpu__clear_all(struct fpu *fpu); extern int fpu__exception_code(struct fpu *fpu, int trap_nr); extern int dump_fpu(struct pt_regs *ptregs, struct user_i387_struct *fpstate); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 12c7084..06c8189 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -291,15 +291,13 @@ void fpu__drop(struct fpu *fpu) } /* - * Clear FPU registers by setting them up from - * the init fpstate: + * Clear FPU registers by setting them up from the init fpstate. + * Caller must do fpregs_[un]lock() around it. */ -static inline void copy_init_fpstate_to_fpregs(void) +static inline void copy_init_fpstate_to_fpregs(u64 features_mask) { - fpregs_lock(); - if (use_xsave()) - copy_kernel_to_xregs(&init_fpstate.xsave, -1); + copy_kernel_to_xregs(&init_fpstate.xsave, features_mask); else if (static_cpu_has(X86_FEATURE_FXSR)) copy_kernel_to_fxregs(&init_fpstate.fxsave); else @@ -307,9 +305,6 @@ static inline void copy_init_fpstate_to_fpregs(void) if (boot_cpu_has(X86_FEATURE_OSPKE)) copy_init_pkru_to_fpregs(); - - fpregs_mark_activate(); - fpregs_unlock(); } /* @@ -318,18 +313,40 @@ static inline void copy_init_fpstate_to_fpregs(void) * Called by sys_execve(), by the signal handler code and by various * error paths. */ -void fpu__clear(struct fpu *fpu) +static void fpu__clear(struct fpu *fpu, bool user_only) { - WARN_ON_FPU(fpu != ¤t->thread.fpu); /* Almost certainly an anomaly */ + WARN_ON_FPU(fpu != ¤t->thread.fpu); - fpu__drop(fpu); + if (!static_cpu_has(X86_FEATURE_FPU)) { + fpu__drop(fpu); + fpu__initialize(fpu); + return; + } - /* - * Make sure fpstate is cleared and initialized. - */ - fpu__initialize(fpu); - if (static_cpu_has(X86_FEATURE_FPU)) - copy_init_fpstate_to_fpregs(); + fpregs_lock(); + + if (user_only) { + if (!fpregs_state_valid(fpu, smp_processor_id()) && + xfeatures_mask_supervisor()) + copy_kernel_to_xregs(&fpu->state.xsave, + xfeatures_mask_supervisor()); + copy_init_fpstate_to_fpregs(xfeatures_mask_user()); + } else { + copy_init_fpstate_to_fpregs(xfeatures_mask_all); + } + + fpregs_mark_activate(); + fpregs_unlock(); +} + +void fpu__clear_user_states(struct fpu *fpu) +{ + fpu__clear(fpu, true); +} + +void fpu__clear_all(struct fpu *fpu) +{ + fpu__clear(fpu, false); } /* diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 3df0cfa..cd6eafb 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -289,7 +289,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) IS_ENABLED(CONFIG_IA32_EMULATION)); if (!buf) { - fpu__clear(fpu); + fpu__clear_user_states(fpu); return 0; } @@ -416,7 +416,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size) err_out: if (ret) - fpu__clear(fpu); + fpu__clear_user_states(fpu); return ret; } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9da70b2..de182b8 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -191,7 +191,7 @@ void flush_thread(void) flush_ptrace_hw_breakpoint(tsk); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); - fpu__clear(&tsk->thread.fpu); + fpu__clear_all(&tsk->thread.fpu); } void disable_TSC(void) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 83b74fb..0052bbe 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -732,7 +732,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs) /* * Ensure the signal handler starts with the new fpu state. */ - fpu__clear(fpu); + fpu__clear_user_states(fpu); } signal_setup_done(failed, ksig, stepping); }
