From 4b384f318cfadddf5726dd6997a2b2d91fd2b6c9 Mon Sep 17 00:00:00 2001 From: Robert Watson Date: Sat, 9 Jan 2021 08:38:11 +0000 Subject: Changes that improve DTrace FBT reliability on freebsd/arm64: - Implement a dtrace_getnanouptime(), matching the existing dtrace_getnanotime(), to avoid DTrace calling out to a potentially instrumentable function. (These should probably both be under KDTRACE_HOOKS. Also, it's not clear to me that they are correct implementations for the DTrace thread time functions they are used in .. fixes for another commit.) - Don't allow FBT to instrument functions involved in EL1 exception handling that are involved in FBT trap processing: handle_el1h_sync() and do_el1h_sync(). - Don't allow FBT to instrument DDB and KDB functions, as that makes it rather harder to debug FBT problems. Prior to these changes, use of FBT on FreeBSD/arm64 rapidly led to kernel panics due to recursion in DTrace. Reliable FBT on FreeBSD/arm64 is reliant on another change from @andrew to have the aarch64 instrumentor more carefully check that instructions it replaces are against the stack pointer, which can otherwise lead to memory corruption. That change remains under review. MFC after: 2 weeks Reviewed by: andrew, kp, markj (earlier version), jrtc27 (earlier version) Differential revision: https://reviews.freebsd.org/D27766 --- cpukit/score/src/kern_tc.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'cpukit/score/src/kern_tc.c') diff --git a/cpukit/score/src/kern_tc.c b/cpukit/score/src/kern_tc.c index 39e67ede19..799d27c0ac 100644 --- a/cpukit/score/src/kern_tc.c +++ b/cpukit/score/src/kern_tc.c @@ -301,6 +301,7 @@ static void _Timecounter_Windup(struct bintime *new_boottimebin, #endif /* __rtems__ */ void dtrace_getnanotime(struct timespec *tsp); +void dtrace_getnanouptime(struct timespec *tsp); #ifndef __rtems__ static int @@ -1173,6 +1174,20 @@ dtrace_getnanotime(struct timespec *tsp) GETTHMEMBER(tsp, th_nanotime); } + +/* + * This is a clone of getnanouptime used for time since boot. + * The dtrace_ prefix prevents fbt from creating probes for + * it so an uptime that can be safely used in all fbt probes. + */ +void +dtrace_getnanouptime(struct timespec *tsp) +{ + struct bintime bt; + + GETTHMEMBER(&bt, th_offset); + bintime2timespec(&bt, tsp); +} #endif /* __rtems__ */ #ifdef FFCLOCK -- cgit v1.2.3