Adding TIF_PERF_USER_DATA bit to be able to limit the code area where the perf's delayed user data retrieval is possible.
Task which is marked with TIF_PERF_USER_DATA bit, will do the slow syscall path and mark the 'safe area' to trigger user data harvest through the task_work by setting up its perf_user_data_allowed bit. Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Jiri Olsa <[email protected]> --- arch/x86/entry/common.c | 6 ++++++ arch/x86/include/asm/thread_info.h | 4 +++- include/linux/sched.h | 3 +++ 3 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index d7d3cc24baf4..29d9e5ef0c75 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -77,6 +77,9 @@ static long syscall_trace_enter(struct pt_regs *regs) work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY; + if (unlikely(work & _TIF_PERF_USER_DATA)) + current->perf_user_data_allowed = 1; + if (unlikely(work & _TIF_SYSCALL_EMU)) emulated = true; @@ -191,6 +194,9 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs) cached_flags = READ_ONCE(ti->flags); + if (unlikely(cached_flags & _TIF_PERF_USER_DATA)) + current->perf_user_data_allowed = 0; + if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS)) exit_to_usermode_loop(regs, cached_flags); diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 00223333821a..f664f4bd25ac 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -80,6 +80,7 @@ struct thread_info { #define TIF_SIGPENDING 2 /* signal pending */ #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ #define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/ +#define TIF_PERF_USER_DATA 5 /* enable safe area for perf user data retrieval */ #define TIF_SYSCALL_EMU 6 /* syscall emulation active */ #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ #define TIF_SECCOMP 8 /* secure computing */ @@ -106,6 +107,7 @@ struct thread_info { #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) #define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP) +#define _TIF_PERF_USER_DATA (1 << TIF_PERF_USER_DATA) #define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) #define _TIF_SECCOMP (1 << TIF_SECCOMP) @@ -133,7 +135,7 @@ struct thread_info { #define _TIF_WORK_SYSCALL_ENTRY \ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \ _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \ - _TIF_NOHZ) + _TIF_NOHZ | _TIF_PERF_USER_DATA) /* work to do on any return to user space */ #define _TIF_ALLWORK_MASK \ diff --git a/include/linux/sched.h b/include/linux/sched.h index d2588263a989..6e8079524010 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -653,6 +653,9 @@ struct task_struct { /* disallow userland-initiated cgroup migration */ unsigned no_cgroup_migration:1; #endif +#ifdef CONFIG_PERF_EVENTS + unsigned perf_user_data_allowed:1; +#endif unsigned long atomic_flags; /* Flags requiring atomic access. */ -- 2.13.6
