Messages in this thread | | | Date | Sun, 15 Mar 2009 20:56:50 +0100 | From | Frederic Weisbecker <> | Subject | Re: [RFC patch 19/21] LTTng Linux Kernel Trace Thread Flag x86 |
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On Sun, Mar 15, 2009 at 03:03:59PM -0400, Mathieu Desnoyers wrote: > Add a thread flag to activate system-wide syscall tracing. > > Make x86_64 support TIF_SYSCALL_TRACE async flag set in entry.S
x86-32 :-)
> When the flag is inactive upon syscall entry and concurrently activated before > exit, we seem to reach a state where the top of stack is incorrect upon return > to user space. > > Fix this by fixing the top of stack and jumping to int_ret_from_sys_call if we > detect that thread flags has been modified.
I don't see where you do that. May be you forgot some parts that match your changelog?
> > We make sure that the thread flag read is coherent between our new test and the ALLWORK_MASK test by first saving it in a register used for both comparisons.
Ditto.
Thanks, Frederic.
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > CC: Andi Kleen <ak@muc.de> > CC: Thomas Gleixner <tglx@linutronix.de> > CC: Ingo Molnar <mingo@redhat.com> > CC: H. Peter Anvin <hpa@zytor.com> > --- > arch/x86/include/asm/thread_info.h | 9 ++++++--- > arch/x86/kernel/entry_32.S | 3 ++- > 2 files changed, 8 insertions(+), 4 deletions(-) > > Index: linux-2.6-lttng/arch/x86/include/asm/thread_info.h > =================================================================== > --- linux-2.6-lttng.orig/arch/x86/include/asm/thread_info.h 2009-01-14 22:10:38.000000000 -0500 > +++ linux-2.6-lttng/arch/x86/include/asm/thread_info.h 2009-01-14 22:25:08.000000000 -0500 > @@ -79,6 +79,7 @@ struct thread_info { > #define TIF_SYSCALL_EMU 6 /* syscall emulation active */ > #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ > #define TIF_SECCOMP 8 /* secure computing */ > +#define TIF_KERNEL_TRACE 9 /* kernel trace active */ > #define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */ > #define TIF_NOTSC 16 /* TSC is not accessible in userland */ > #define TIF_IA32 17 /* 32bit process */ > @@ -102,6 +103,7 @@ struct thread_info { > #define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU) > #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) > #define _TIF_SECCOMP (1 << TIF_SECCOMP) > +#define _TIF_KERNEL_TRACE (1 << TIF_KERNEL_TRACE) > #define _TIF_MCE_NOTIFY (1 << TIF_MCE_NOTIFY) > #define _TIF_NOTSC (1 << TIF_NOTSC) > #define _TIF_IA32 (1 << TIF_IA32) > @@ -117,17 +119,18 @@ struct thread_info { > > /* work to do in syscall_trace_enter() */ > #define _TIF_WORK_SYSCALL_ENTRY \ > - (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | \ > + (_TIF_SYSCALL_TRACE | _TIF_KERNEL_TRACE | _TIF_SYSCALL_EMU | \ > _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | _TIF_SINGLESTEP) > > /* work to do in syscall_trace_leave() */ > #define _TIF_WORK_SYSCALL_EXIT \ > - (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP) > + (_TIF_SYSCALL_TRACE | _TIF_KERNEL_TRACE | _TIF_SYSCALL_AUDIT | \ > + _TIF_SINGLESTEP) > > /* work to do on interrupt/exception return */ > #define _TIF_WORK_MASK \ > (0x0000FFFF & \ > - ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT| \ > + ~(_TIF_SYSCALL_TRACE|_TIF_KERNEL_TRACE|_TIF_SYSCALL_AUDIT| \ > _TIF_SINGLESTEP|_TIF_SECCOMP|_TIF_SYSCALL_EMU)) > > /* work to do on any return to user space */ > Index: linux-2.6-lttng/arch/x86/kernel/entry_32.S > =================================================================== > --- linux-2.6-lttng.orig/arch/x86/kernel/entry_32.S 2009-01-14 22:22:40.000000000 -0500 > +++ linux-2.6-lttng/arch/x86/kernel/entry_32.S 2009-01-14 22:25:44.000000000 -0500 > @@ -571,7 +571,8 @@ END(syscall_trace_entry) > # perform syscall exit tracing > ALIGN > syscall_exit_work: > - testb $_TIF_WORK_SYSCALL_EXIT, %cl > + /* Note, _TIF_KERNEL_TRACE is bit number 9, and so it needs testw and not testb */ > + testw $_TIF_WORK_SYSCALL_EXIT, %cx > jz work_pending > TRACE_IRQS_ON > ENABLE_INTERRUPTS(CLBR_ANY) # could let syscall_trace_leave() call > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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