Messages in this thread |  | | Date | Thu, 7 Feb 2013 01:29:39 +0100 | Subject | Re: [RFC PATCH 1/5] powerpc: Syscall hooks for context tracking subsystem | From | Frederic Weisbecker <> |
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2013/2/1 Li Zhong <zhong@linux.vnet.ibm.com>: > This is the syscall slow path hooks for context tracking subsystem, > corresponding to > [PATCH] x86: Syscall hooks for userspace RCU extended QS > commit bf5a3c13b939813d28ce26c01425054c740d6731 > > TIF_MEMDIE is moved to the second 16-bits (with value 17), as it seems there > is no asm code using it. TIF_NOHZ is added to _TIF_SYCALL_T_OR_A, so it is > better for it to be in the same 16 bits with others in the group, so in the > asm code, andi. with this group could work. > > Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> > --- > arch/powerpc/include/asm/thread_info.h | 7 +++++-- > arch/powerpc/kernel/ptrace.c | 5 +++++ > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h > index 406b7b9..414a261 100644 > --- a/arch/powerpc/include/asm/thread_info.h > +++ b/arch/powerpc/include/asm/thread_info.h > @@ -97,7 +97,7 @@ static inline struct thread_info *current_thread_info(void) > #define TIF_PERFMON_CTXSW 6 /* perfmon needs ctxsw calls */ > #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ > #define TIF_SINGLESTEP 8 /* singlestepping active */ > -#define TIF_MEMDIE 9 /* is terminating due to OOM killer */ > +#define TIF_NOHZ 9 /* in adaptive nohz mode */ > #define TIF_SECCOMP 10 /* secure computing */ > #define TIF_RESTOREALL 11 /* Restore all regs (implies NOERROR) */ > #define TIF_NOERROR 12 /* Force successful syscall return */ > @@ -106,6 +106,7 @@ static inline struct thread_info *current_thread_info(void) > #define TIF_SYSCALL_TRACEPOINT 15 /* syscall tracepoint instrumentation */ > #define TIF_EMULATE_STACK_STORE 16 /* Is an instruction emulation > for stack store? */ > +#define TIF_MEMDIE 17 /* is terminating due to OOM killer */ > > /* as above, but as bit values */ > #define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE) > @@ -124,8 +125,10 @@ static inline struct thread_info *current_thread_info(void) > #define _TIF_UPROBE (1<<TIF_UPROBE) > #define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT) > #define _TIF_EMULATE_STACK_STORE (1<<TIF_EMULATE_STACK_STORE) > +#define _TIF_NOHZ (1<<TIF_NOHZ) > #define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ > - _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT) > + _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \ > + _TIF_NOHZ) > > #define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \ > _TIF_NOTIFY_RESUME | _TIF_UPROBE) > diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c > index c497000..62238dd 100644 > --- a/arch/powerpc/kernel/ptrace.c > +++ b/arch/powerpc/kernel/ptrace.c > @@ -32,6 +32,7 @@ > #include <trace/syscall.h> > #include <linux/hw_breakpoint.h> > #include <linux/perf_event.h> > +#include <linux/context_tracking.h> > > #include <asm/uaccess.h> > #include <asm/page.h> > @@ -1745,6 +1746,8 @@ long do_syscall_trace_enter(struct pt_regs *regs) > { > long ret = 0; > > + user_exit(); > + > secure_computing_strict(regs->gpr[0]); > > if (test_thread_flag(TIF_SYSCALL_TRACE) && > @@ -1789,4 +1792,6 @@ void do_syscall_trace_leave(struct pt_regs *regs) > step = test_thread_flag(TIF_SINGLESTEP); > if (step || test_thread_flag(TIF_SYSCALL_TRACE)) > tracehook_report_syscall_exit(regs, step); > + > + user_enter();
In x86-64, schedule_user() and do_notify_resume() can be called before syscall_trace_leave(). As a result we may be entering syscall_trace_leave() in user mode (from a context tracking POV). To fix this I added a call to user_exit() on the very beginning of that function.
You can find the details in 2c5594df344cd1ff0cc9bf007dea3235582b3acf ("rcu: Fix unrecovered RCU user mode in syscall_trace_leave()").
Could this problem happen in ppc as well?
Thanks.
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