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f2b375756c
Due to a blatant design error, SYSENTER doesn't clear TF (single-step).
As a result, if a user does SYSENTER with TF set, we will single-step
through the kernel until something clears TF. There is absolutely
nothing we can do to prevent this short of turning off SYSENTER [1].
Simplify the handling considerably with two changes:
1. We already sanitize EFLAGS in SYSENTER to clear NT and AC. We can
add TF to that list of flags to sanitize with no overhead whatsoever.
2. Teach do_debug() to ignore single-step traps in the SYSENTER prologue.
That's all we need to do.
Don't get too excited -- our handling is still buggy on 32-bit
kernels. There's nothing wrong with the SYSENTER code itself, but
the #DB prologue has a clever fixup for traps on the very first
instruction of entry_SYSENTER_32, and the fixup doesn't work quite
correctly. The next two patches will fix that.
[1] We could probably prevent it by forcing BTF on at all times and
making sure we clear TF before any branches in the SYSENTER
code. Needless to say, this is a bad idea.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a30d2ea06fe4b621fe6a9ef911b02c0f38feb6f2.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
35 lines
744 B
C
35 lines
744 B
C
#ifndef _ASM_X86_PROTO_H
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#define _ASM_X86_PROTO_H
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#include <asm/ldt.h>
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/* misc architecture specific prototypes */
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void syscall_init(void);
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#ifdef CONFIG_X86_64
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void entry_SYSCALL_64(void);
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#endif
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#ifdef CONFIG_X86_32
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void entry_INT80_32(void);
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void entry_SYSENTER_32(void);
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void __begin_SYSENTER_singlestep_region(void);
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void __end_SYSENTER_singlestep_region(void);
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#endif
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#ifdef CONFIG_IA32_EMULATION
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void entry_SYSENTER_compat(void);
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void __end_entry_SYSENTER_compat(void);
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void entry_SYSCALL_compat(void);
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void entry_INT80_compat(void);
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#endif
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void x86_configure_nx(void);
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void x86_report_nx(void);
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extern int reboot_force;
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long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
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#endif /* _ASM_X86_PROTO_H */
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