forked from Minki/linux
6342adcaa6
Commit2991552447("entry: Drop usage of TIF flags in the generic syscall code") introduced a bug on architectures using the generic syscall entry code, in which processes stopped by PTRACE_SYSCALL do not trap on syscall return after receiving a TIF_SINGLESTEP. The reason is that the meaning of TIF_SINGLESTEP flag is overloaded to cause the trap after a system call is executed, but since the above commit, the syscall call handler only checks for the SYSCALL_WORK flags on the exit work. Split the meaning of TIF_SINGLESTEP such that it only means single-step mode, and create a new type of SYSCALL_WORK to request a trap immediately after a syscall in single-step mode. In the current implementation, the SYSCALL_WORK flag shadows the TIF_SINGLESTEP flag for simplicity. Update x86 to flip this bit when a tracer enables single stepping. Fixes:2991552447("entry: Drop usage of TIF flags in the generic syscall code") Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kyle Huey <me@kylehuey.com> Link: https://lore.kernel.org/r/87h7mtc9pr.fsf_-_@collabora.com
83 lines
2.4 KiB
C
83 lines
2.4 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/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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/* Check that the stack and regs on entry from user mode are sane. */
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static __always_inline void arch_check_user_regs(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 (boot_cpu_has(X86_FEATURE_SMAP) ||
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(IS_ENABLED(CONFIG_64_BIT) && boot_cpu_has(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_check_user_regs arch_check_user_regs
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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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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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fpregs_assert_state_consistent();
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if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
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switch_fpu_return();
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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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#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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mds_user_clear_cpu_buffers();
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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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