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If CONFIG_X86_DEBUG_FPU=Y, arch_exit_to_user_mode_prepare() calls arch_exit_work() even if ti_work == 0. There only reason is that we want to call fpregs_assert_state_consistent() if TIF_NEED_FPU_LOAD is not set. This looks confusing. arch_exit_to_user_mode_prepare() can just call fpregs_assert_state_consistent() unconditionally, it depends on CONFIG_X86_DEBUG_FPU and checks TIF_NEED_FPU_LOAD itself. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Chang S . Bae <chang.seok.bae@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Brian Gerst <brgerst@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20250503143902.GA9012@redhat.com
105 lines
3 KiB
C
105 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef _ASM_X86_ENTRY_COMMON_H
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#define _ASM_X86_ENTRY_COMMON_H
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#include <linux/randomize_kstack.h>
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#include <linux/user-return-notifier.h>
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#include <asm/nospec-branch.h>
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#include <asm/io_bitmap.h>
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#include <asm/fpu/api.h>
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#include <asm/fred.h>
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/* Check that the stack and regs on entry from user mode are sane. */
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static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
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{
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if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
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/*
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* Make sure that the entry code gave us a sensible EFLAGS
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* register. Native because we want to check the actual CPU
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* state, not the interrupt state as imagined by Xen.
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*/
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unsigned long flags = native_save_fl();
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unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT;
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/*
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* For !SMAP hardware we patch out CLAC on entry.
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*/
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if (cpu_feature_enabled(X86_FEATURE_SMAP) ||
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cpu_feature_enabled(X86_FEATURE_XENPV))
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mask |= X86_EFLAGS_AC;
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WARN_ON_ONCE(flags & mask);
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/* We think we came from user mode. Make sure pt_regs agrees. */
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WARN_ON_ONCE(!user_mode(regs));
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/*
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* All entries from user mode (except #DF) should be on the
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* normal thread stack and should have user pt_regs in the
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* correct location.
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*/
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WARN_ON_ONCE(!on_thread_stack());
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WARN_ON_ONCE(regs != task_pt_regs(current));
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}
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}
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#define arch_enter_from_user_mode arch_enter_from_user_mode
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static inline void arch_exit_work(unsigned long ti_work)
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{
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if (ti_work & _TIF_USER_RETURN_NOTIFY)
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fire_user_return_notifiers();
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if (unlikely(ti_work & _TIF_IO_BITMAP))
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tss_update_io_bitmap();
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if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
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switch_fpu_return();
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}
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static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
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unsigned long ti_work)
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{
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fpregs_assert_state_consistent();
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if (unlikely(ti_work))
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arch_exit_work(ti_work);
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fred_update_rsp0();
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#ifdef CONFIG_COMPAT
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/*
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* Compat syscalls set TS_COMPAT. Make sure we clear it before
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* returning to user mode. We need to clear it *after* signal
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* handling, because syscall restart has a fixup for compat
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* syscalls. The fixup is exercised by the ptrace_syscall_32
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* selftest.
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*
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* We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
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* special case only applies after poking regs and before the
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* very next return to user mode.
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*/
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current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED);
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#endif
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/*
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* This value will get limited by KSTACK_OFFSET_MAX(), which is 10
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* bits. The actual entropy will be further reduced by the compiler
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* when applying stack alignment constraints (see cc_stack_align4/8 in
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* arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
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* low bits from any entropy chosen here.
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*
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* Therefore, final stack offset entropy will be 7 (x86_64) or
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* 8 (ia32) bits.
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*/
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choose_random_kstack_offset(rdtsc());
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}
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#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
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static __always_inline void arch_exit_to_user_mode(void)
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{
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amd_clear_divider();
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}
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#define arch_exit_to_user_mode arch_exit_to_user_mode
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#endif
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