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x86 single_step: TIF_FORCED_TF

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This changes the single-step support to use a new thread_info flag
TIF_FORCED_TF instead of the PT_DTRACE flag in task_struct.ptrace.
This keeps arch implementation uses out of this non-arch field.

This changes the ptrace access to eflags to mask TF and maintain
the TIF_FORCED_TF flag directly if userland sets TF, instead of
relying on ptrace_signal_deliver.  The 64-bit and 32-bit kernels
are harmonized on this same behavior.  The ptrace_signal_deliver
approach works now, but this change makes the low-level register
access code reliable when called from different contexts than a
ptrace stop, which will be possible in the future.

The 64-bit do_debug exception handler is also changed not to clear TF
from user-mode registers.  This matches the 32-bit kernel's behavior.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Roland McGrath 2008-01-30 13:30:50 +01:00 committed by Ingo Molnar
parent 7122ec8158
commit e1f287735c
12 changed files with 79 additions and 59 deletions
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20
arch/x86/ia32/ptrace32.c
View file

@ -89,6 +89,15 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 val)
__u64 *flags = &stack[offsetof(struct pt_regs, eflags)/8];
val &= FLAG_MASK;
/*
* If the user value contains TF, mark that
* it was not "us" (the debugger) that set it.
* If not, make sure it stays set if we had.
*/
if (val & X86_EFLAGS_TF)
clear_tsk_thread_flag(child, TIF_FORCED_TF);
else if (test_tsk_thread_flag(child, TIF_FORCED_TF))
val |= X86_EFLAGS_TF;
*flags = val | (*flags & ~FLAG_MASK);
break;
}
@ -179,9 +188,17 @@ static int getreg32(struct task_struct *child, unsigned regno, u32 *val)
R32(eax, rax);
R32(orig_eax, orig_rax);
R32(eip, rip);
R32(eflags, eflags);
R32(esp, rsp);
case offsetof(struct user32, regs.eflags):
/*
* If the debugger set TF, hide it from the readout.
*/
*val = stack[offsetof(struct pt_regs, eflags)/8];
if (test_tsk_thread_flag(child, TIF_FORCED_TF))
*val &= ~X86_EFLAGS_TF;
break;
case offsetof(struct user32, u_debugreg[0]):
*val = child->thread.debugreg0;
break;
@ -425,4 +442,3 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
put_task_struct(child);
return ret;
}

3
arch/x86/kernel/process_32.c
View file

@ -817,9 +817,6 @@ asmlinkage int sys_execve(struct pt_regs regs)
(char __user * __user *) regs.edx,
&regs);
if (error == 0) {
task_lock(current);
current->ptrace &= ~PT_DTRACE;
task_unlock(current);
/* Make sure we don't return using sysenter.. */
set_thread_flag(TIF_IRET);
}

5
arch/x86/kernel/process_64.c
View file

@ -709,11 +709,6 @@ long sys_execve(char __user *name, char __user * __user *argv,
if (IS_ERR(filename))
return error;
error = do_execve(filename, argv, envp, &regs);
if (error == 0) {
task_lock(current);
current->ptrace &= ~PT_DTRACE;
task_unlock(current);
}
putname(filename);
return error;
}

17
arch/x86/kernel/ptrace_32.c
View file

@ -104,6 +104,15 @@ static int putreg(struct task_struct *child,
break;
case EFL:
value &= FLAG_MASK;
/*
* If the user value contains TF, mark that
* it was not "us" (the debugger) that set it.
* If not, make sure it stays set if we had.
*/
if (value & X86_EFLAGS_TF)
clear_tsk_thread_flag(child, TIF_FORCED_TF);
else if (test_tsk_thread_flag(child, TIF_FORCED_TF))
value |= X86_EFLAGS_TF;
value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
break;
}
@ -119,6 +128,14 @@ static unsigned long getreg(struct task_struct *child,
unsigned long retval = ~0UL;
switch (regno >> 2) {
case EFL:
/*
* If the debugger set TF, hide it from the readout.
*/
retval = get_stack_long(child, EFL_OFFSET);
if (test_tsk_thread_flag(child, TIF_FORCED_TF))
retval &= ~X86_EFLAGS_TF;
break;
case GS:
retval = child->thread.gs;
break;

20
arch/x86/kernel/ptrace_64.c
View file

@ -143,6 +143,15 @@ static int putreg(struct task_struct *child,
return 0;
case offsetof(struct user_regs_struct, eflags):
value &= FLAG_MASK;
/*
* If the user value contains TF, mark that
* it was not "us" (the debugger) that set it.
* If not, make sure it stays set if we had.
*/
if (value & X86_EFLAGS_TF)
clear_tsk_thread_flag(child, TIF_FORCED_TF);
else if (test_tsk_thread_flag(child, TIF_FORCED_TF))
value |= X86_EFLAGS_TF;
tmp = get_stack_long(child, EFL_OFFSET);
tmp &= ~FLAG_MASK;
value |= tmp;
@ -189,6 +198,17 @@ static unsigned long getreg(struct task_struct *child, unsigned long regno)
if (child->thread.gsindex != GS_TLS_SEL)
return 0;
return get_desc_base(&child->thread.tls_array[GS_TLS]);
case offsetof(struct user_regs_struct, eflags):
/*
* If the debugger set TF, hide it from the readout.
*/
regno = regno - sizeof(struct pt_regs);
val = get_stack_long(child, regno);
if (test_tsk_thread_flag(child, TIF_IA32))
val &= 0xffffffff;
if (test_tsk_thread_flag(child, TIF_FORCED_TF))
val &= ~X86_EFLAGS_TF;
return val;
default:
regno = regno - sizeof(struct pt_regs);
val = get_stack_long(child, regno);

12
arch/x86/kernel/signal_32.c
View file

@ -545,14 +545,12 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
}
/*
* If TF is set due to a debugger (PT_DTRACE), clear the TF flag so
* that register information in the sigcontext is correct.
* If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
* flag so that register information in the sigcontext is correct.
*/
if (unlikely(regs->eflags & TF_MASK)
&& likely(current->ptrace & PT_DTRACE)) {
current->ptrace &= ~PT_DTRACE;
regs->eflags &= ~TF_MASK;
}
if (unlikely(regs->eflags & X86_EFLAGS_TF) &&
likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
regs->eflags &= ~X86_EFLAGS_TF;
/* Set up the stack frame */
if (ka->sa.sa_flags & SA_SIGINFO)

14
arch/x86/kernel/signal_64.c
View file

@ -349,16 +349,12 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
}
/*
* If TF is set due to a debugger (PT_DTRACE), clear the TF
* flag so that register information in the sigcontext is
* correct.
* If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
* flag so that register information in the sigcontext is correct.
*/
if (unlikely(regs->eflags & TF_MASK)) {
if (likely(current->ptrace & PT_DTRACE)) {
current->ptrace &= ~PT_DTRACE;
regs->eflags &= ~TF_MASK;
}
}
if (unlikely(regs->eflags & X86_EFLAGS_TF) &&
likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
regs->eflags &= ~X86_EFLAGS_TF;
#ifdef CONFIG_IA32_EMULATION
if (test_thread_flag(TIF_IA32)) {

9
arch/x86/kernel/step.c
View file

@ -135,7 +135,7 @@ void user_enable_single_step(struct task_struct *child)
if (is_setting_trap_flag(child, regs))
return;
child->ptrace |= PT_DTRACE;
set_tsk_thread_flag(child, TIF_FORCED_TF);
}
void user_disable_single_step(struct task_struct *child)
@ -144,9 +144,6 @@ void user_disable_single_step(struct task_struct *child)
clear_tsk_thread_flag(child, TIF_SINGLESTEP);
/* But touch TF only if it was set by us.. */
if (child->ptrace & PT_DTRACE) {
struct pt_regs *regs = task_pt_regs(child);
regs->eflags &= ~X86_EFLAGS_TF;
child->ptrace &= ~PT_DTRACE;
}
if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))
task_pt_regs(child)->eflags &= ~X86_EFLAGS_TF;
}

23
arch/x86/kernel/traps_64.c
View file

@ -865,27 +865,14 @@ asmlinkage void __kprobes do_debug(struct pt_regs * regs,
tsk->thread.debugreg6 = condition;
/* Mask out spurious TF errors due to lazy TF clearing */
/*
* Single-stepping through TF: make sure we ignore any events in
* kernel space (but re-enable TF when returning to user mode).
*/
if (condition & DR_STEP) {
/*
* The TF error should be masked out only if the current
* process is not traced and if the TRAP flag has been set
* previously by a tracing process (condition detected by
* the PT_DTRACE flag); remember that the i386 TRAP flag
* can be modified by the process itself in user mode,
* allowing programs to debug themselves without the ptrace()
* interface.
*/
if (!user_mode(regs))
goto clear_TF_reenable;
/*
* Was the TF flag set by a debugger? If so, clear it now,
* so that register information is correct.
*/
if (tsk->ptrace & PT_DTRACE) {
regs->eflags &= ~TF_MASK;
tsk->ptrace &= ~PT_DTRACE;
}
}
/* Ok, finally something we can handle */

11
include/asm-x86/signal.h
View file

@ -245,21 +245,14 @@ static __inline__ int sigfindinword(unsigned long word)
struct pt_regs;
#define ptrace_signal_deliver(regs, cookie) \
do { \
if (current->ptrace & PT_DTRACE) { \
current->ptrace &= ~PT_DTRACE; \
(regs)->eflags &= ~TF_MASK; \
} \
} while (0)
#else /* __i386__ */
#undef __HAVE_ARCH_SIG_BITOPS
#endif /* !__i386__ */
#define ptrace_signal_deliver(regs, cookie) do { } while (0)
#endif /* !__i386__ */
#endif /* __KERNEL__ */
#endif /* __ASSEMBLY__ */

2
include/asm-x86/thread_info_32.h
View file

@ -138,6 +138,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_IO_BITMAP 18 /* uses I/O bitmap */
#define TIF_FREEZE 19 /* is freezing for suspend */
#define TIF_NOTSC 20 /* TSC is not accessible in userland */
#define TIF_FORCED_TF 21 /* true if TF in eflags artificially */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@ -153,6 +154,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
#define _TIF_NOTSC (1<<TIF_NOTSC)
#define _TIF_FORCED_TF (1<<TIF_FORCED_TF)
/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \

2
include/asm-x86/thread_info_64.h
View file

@ -121,6 +121,7 @@ static inline struct thread_info *stack_thread_info(void)
#define TIF_DEBUG 21 /* uses debug registers */
#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
#define TIF_FREEZE 23 /* is freezing for suspend */
#define TIF_FORCED_TF 24 /* true if TF in eflags artificially */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@ -138,6 +139,7 @@ static inline struct thread_info *stack_thread_info(void)
#define _TIF_DEBUG (1<<TIF_DEBUG)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
#define _TIF_FORCED_TF (1<<TIF_FORCED_TF)
/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \