When context tracking (TIF_NOHZ), force the syscall slow path by adding _TIF_NOHZ to _TIF_SYSCALL_WORK. Use the syscall trace enter/exit paths to do the context tracking. This corresponds to commit bf5a3c13 (x86: Syscall hooks for userspace RCU extended QS.)
Also cover the special case in syscall_trace_exit() based on commit 2c5594df (rcu: Fix unrecovered RCU user mode in syscall_trace_leave()) for x86.
Special thanks to Mats Liljegren for collaboration and additional testing.
Cc: Mats Liljegren mats.liljegren@enea.com Signed-off-by: Kevin Hilman khilman@linaro.org --- arch/arm/include/asm/thread_info.h | 4 +++- arch/arm/kernel/ptrace.c | 11 +++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index cddda1f..e4c7e21 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -152,6 +152,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, #define TIF_SYSCALL_AUDIT 9 #define TIF_SYSCALL_TRACEPOINT 10 #define TIF_SECCOMP 11 /* seccomp syscall filtering active */ +#define TIF_NOHZ 12 /* in adaptive nohz mode */ #define TIF_USING_IWMMXT 17 #define TIF_MEMDIE 18 /* is terminating due to OOM killer */ #define TIF_RESTORE_SIGMASK 20 @@ -165,10 +166,11 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT) #define _TIF_SECCOMP (1 << TIF_SECCOMP) #define _TIF_USING_IWMMXT (1 << TIF_USING_IWMMXT) +#define _TIF_NOHZ (1 << TIF_NOHZ)
/* Checks for any syscall work in entry-common.S */ #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ - _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP) + _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | _TIF_NOHZ)
/* * Change these and you break ASM code in entry-common.S diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 03deeff..3ab329a 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -26,6 +26,7 @@ #include <linux/audit.h> #include <linux/tracehook.h> #include <linux/unistd.h> +#include <linux/context_tracking.h>
#include <asm/pgtable.h> #include <asm/traps.h> @@ -941,6 +942,8 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno) { current_thread_info()->syscall = scno;
+ user_exit(); + /* Do the secure computing check first; failures should be fast. */ if (secure_computing(scno) == -1) return -1; @@ -960,6 +963,12 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno) asmlinkage void syscall_trace_exit(struct pt_regs *regs) { /* + * We may come here right after calling do_work_pending() in + * which case we can be in context_tracking user mode. + */ + user_exit(); + + /* * Audit the syscall before anything else, as a debugger may * come in and change the current registers. */ @@ -976,4 +985,6 @@ asmlinkage void syscall_trace_exit(struct pt_regs *regs)
if (test_thread_flag(TIF_SYSCALL_TRACE)) tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT); + + user_enter(); }