Date: Fri, 27 Apr 2018 15:16:34 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r333064 - in head/sys: cddl/dev/systrace kern sys Message-ID: <201804271516.w3RFGYFU056346@repo.freebsd.org>
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Author: mjg Date: Fri Apr 27 15:16:34 2018 New Revision: 333064 URL: https://svnweb.freebsd.org/changeset/base/333064 Log: systrace: track it like sdt probes While here predict false. Note the code is wrong (regardless of this change). Dereference of the pointer can race with module unload. A fix would set the probe to a nop stub instead of NULL. Modified: head/sys/cddl/dev/systrace/systrace.c head/sys/kern/kern_dtrace.c head/sys/kern/subr_syscall.c head/sys/sys/sysent.h Modified: head/sys/cddl/dev/systrace/systrace.c ============================================================================== --- head/sys/cddl/dev/systrace/systrace.c Fri Apr 27 13:59:24 2018 (r333063) +++ head/sys/cddl/dev/systrace/systrace.c Fri Apr 27 15:16:34 2018 (r333064) @@ -135,6 +135,8 @@ extern const char *freebsd32_syscallnames[]; #error 1 << SYSTRACE_SHIFT must exceed number of system calls #endif +static int systrace_enabled_count; + static void systrace_load(void *); static void systrace_unload(void *); @@ -315,6 +317,9 @@ systrace_enable(void *arg, dtrace_id_t id, void *parg) SYSENT[sysnum].sy_entry = id; else SYSENT[sysnum].sy_return = id; + systrace_enabled_count++; + if (systrace_enabled_count == 1) + systrace_enabled = true; } static void @@ -324,6 +329,9 @@ systrace_disable(void *arg, dtrace_id_t id, void *parg SYSENT[sysnum].sy_entry = 0; SYSENT[sysnum].sy_return = 0; + systrace_enabled_count--; + if (systrace_enabled_count == 0) + systrace_enabled = false; } static void Modified: head/sys/kern/kern_dtrace.c ============================================================================== --- head/sys/kern/kern_dtrace.c Fri Apr 27 13:59:24 2018 (r333063) +++ head/sys/kern/kern_dtrace.c Fri Apr 27 15:16:34 2018 (r333064) @@ -56,7 +56,8 @@ dtrace_doubletrap_func_t dtrace_doubletrap_func; dtrace_pid_probe_ptr_t dtrace_pid_probe_ptr; dtrace_return_probe_ptr_t dtrace_return_probe_ptr; -systrace_probe_func_t __read_frequently systrace_probe_func; +bool __read_frequently systrace_enabled; +systrace_probe_func_t systrace_probe_func; /* Return the DTrace process data size compiled in the kernel hooks. */ size_t Modified: head/sys/kern/subr_syscall.c ============================================================================== --- head/sys/kern/subr_syscall.c Fri Apr 27 13:59:24 2018 (r333063) +++ head/sys/kern/subr_syscall.c Fri Apr 27 15:16:34 2018 (r333064) @@ -126,7 +126,8 @@ syscallenter(struct thread *td) #ifdef KDTRACE_HOOKS /* Give the syscall:::entry DTrace probe a chance to fire. */ - if (systrace_probe_func != NULL && sa->callp->sy_entry != 0) + if (__predict_false(systrace_enabled && + sa->callp->sy_entry != 0)) (*systrace_probe_func)(sa, SYSTRACE_ENTRY, 0); #endif @@ -140,7 +141,8 @@ syscallenter(struct thread *td) #ifdef KDTRACE_HOOKS /* Give the syscall:::return DTrace probe a chance to fire. */ - if (systrace_probe_func != NULL && sa->callp->sy_return != 0) + if (__predict_false(systrace_enabled && + sa->callp->sy_return != 0)) (*systrace_probe_func)(sa, SYSTRACE_RETURN, error ? -1 : td->td_retval[0]); #endif Modified: head/sys/sys/sysent.h ============================================================================== --- head/sys/sys/sysent.h Fri Apr 27 13:59:24 2018 (r333063) +++ head/sys/sys/sysent.h Fri Apr 27 15:16:34 2018 (r333064) @@ -53,6 +53,7 @@ typedef void (*systrace_probe_func_t)(struct syscall_a enum systrace_probe_t, int); typedef void (*systrace_args_func_t)(int, void *, uint64_t *, int *); +extern bool systrace_enabled; extern systrace_probe_func_t systrace_probe_func; struct sysent { /* system call table */
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