From: Pierre-Marc Fournier Date: Wed, 20 Jan 2010 06:03:57 +0000 (-0500) Subject: Refactor libinterfork and add support for clone() interception X-Git-Tag: v0.2~47 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=616ed36a65d067de413ac5aca14d165cd5044b96;p=ust.git Refactor libinterfork and add support for clone() interception --- diff --git a/include/Makefile.am b/include/Makefile.am index ea66be8..bb8d2e7 100644 --- a/include/Makefile.am +++ b/include/Makefile.am @@ -1,4 +1,4 @@ nobase_include_HEADERS = ust/immediate.h ust/kernelcompat.h ust/marker.h \ - ust/tracepoint.h ust/processor.h ust/probe.h ust/ust.h + ust/tracepoint.h ust/processor.h ust/probe.h ust/ust.h ust/tracectl.h noinst_HEADERS = share.h usterr.h diff --git a/include/ust/tracectl.h b/include/ust/tracectl.h new file mode 100644 index 0000000..7e3ec19 --- /dev/null +++ b/include/ust/tracectl.h @@ -0,0 +1,14 @@ +#ifndef UST_TRACECTL_H +#define UST_TRACECTL_H + +typedef struct ust_fork_info { + sigset_t orig_sigs; +} ust_fork_info_t; + +extern void ust_potential_exec(void); + +extern void ust_before_fork(ust_fork_info_t *fork_info); +extern void ust_after_fork_parent(ust_fork_info_t *fork_info); +extern void ust_after_fork_child(ust_fork_info_t *fork_info); + +#endif /* UST_TRACECTL_H */ diff --git a/libinterfork/interfork.c b/libinterfork/interfork.c index e9dce9b..a92a2bd 100644 --- a/libinterfork/interfork.c +++ b/libinterfork/interfork.c @@ -20,21 +20,19 @@ #include #include #include +#include +#include +#include +#include #include "usterr.h" -extern void ust_fork(void); -extern void ust_potential_exec(void); - pid_t fork(void) { static pid_t (*plibc_func)(void) = NULL; + ust_fork_info_t fork_info; pid_t retval; - int result; - sigset_t all_sigs; - sigset_t orig_sigs; - if(plibc_func == NULL) { plibc_func = dlsym(RTLD_NEXT, "fork"); if(plibc_func == NULL) { @@ -43,37 +41,17 @@ pid_t fork(void) } } - /* Disable interrupts. This is to avoid that the child - * intervenes before it is properly setup for tracing. It is - * safer to disable all signals, because then we know we are not - * breaking anything by restoring the original mask. - */ - - /* FIXME: - - only do this if tracing is active - */ - - /* Disable signals */ - sigfillset(&all_sigs); - result = sigprocmask(SIG_BLOCK, &all_sigs, &orig_sigs); - if(result == -1) { - PERROR("sigprocmask"); - return -1; - } + ust_before_fork(&fork_info); /* Do the real fork */ retval = plibc_func(); if(retval == 0) { /* child */ - ust_fork(); + ust_after_fork_child(&fork_info); } - - /* Restore signals */ - result = sigprocmask(SIG_BLOCK, &orig_sigs, NULL); - if(result == -1) { - PERROR("sigprocmask"); - return -1; + else { + ust_after_fork_parent(&fork_info); } return retval; @@ -88,7 +66,7 @@ int execve(const char *filename, char *const argv[], char *const envp[]) if(plibc_func == NULL) { plibc_func = dlsym(RTLD_NEXT, "execve"); if(plibc_func == NULL) { - fprintf(stderr, "libcwrap: unable to find execve\n"); + fprintf(stderr, "libinterfork: unable to find execve\n"); return -1; } } @@ -99,3 +77,65 @@ int execve(const char *filename, char *const argv[], char *const envp[]) return retval; } + +struct interfork_clone_info { + int (*fn)(void *); + void *arg; + ust_fork_info_t *fork_info; +}; + +static int clone_fn(void *arg) +{ + struct interfork_clone_info *info = (struct interfork_clone_info *)arg; + + /* clone is now done and we are in child */ + ust_after_fork_child(&info->fork_info); + + return info->fn(info->arg); +} + +int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...) +{ + static int (*plibc_func)(int (*fn)(void *), void *child_stack, int flags, void *arg, pid_t *ptid, struct user_desc *tls, pid_t *ctid) = NULL; + + /* varargs */ + pid_t *ptid; + struct user_desc *tls; + pid_t *ctid; + + int retval; + + va_list ap; + + va_start(ap, arg); + ptid = va_arg(ap, pid_t *); + tls = va_arg(ap, struct user_desc *); + ctid = va_arg(ap, pid_t *); + va_end(ap); + + if(plibc_func == NULL) { + plibc_func = dlsym(RTLD_NEXT, "clone"); + if(plibc_func == NULL) { + fprintf(stderr, "libinterfork: unable to find clone\n"); + return -1; + } + } + + if(flags & CLONE_VM) { + /* creating a thread, no need to intervene, just pass on the arguments */ + retval = plibc_func(fn, child_stack, flags, arg, ptid, tls, ctid); + } + else { + /* creating a real process, we need to intervene */ + struct interfork_clone_info info = { fn: fn, arg: arg }; + + ust_before_fork(&info.fork_info); + + retval = plibc_func(clone_fn, child_stack, flags, &info, ptid, tls, ctid); + + /* The child doesn't get here */ + ust_after_fork_parent(&info.fork_info); + } + + return retval; +} diff --git a/libust/tracectl.c b/libust/tracectl.c index f9312b4..5e59ca7 100644 --- a/libust/tracectl.c +++ b/libust/tracectl.c @@ -30,6 +30,7 @@ #include #include +#include #include "tracer.h" #include "usterr.h" #include "ustcomm.h" @@ -1122,9 +1123,13 @@ void ust_potential_exec(void) * the new process, anytime a process whose memory is not shared with * the parent is created. If this function is not called, the events * of the new process will not be collected. + * + * Signals should be disabled before the fork and reenabled only after + * this call in order to guarantee tracing is not started before ust_fork() + * sanitizes the new process. */ -void ust_fork(void) +static void ust_fork(void) { struct blocked_consumer *bc; struct blocked_consumer *deletable_bc = NULL; @@ -1160,3 +1165,55 @@ void ust_fork(void) inform_consumer_daemon("auto"); } +void ust_before_fork(ust_fork_info_t *fork_info) +{ + /* Disable signals. This is to avoid that the child + * intervenes before it is properly setup for tracing. It is + * safer to disable all signals, because then we know we are not + * breaking anything by restoring the original mask. + */ + sigset_t all_sigs; + int result; + + /* FIXME: + - only do this if tracing is active + */ + + /* Disable signals */ + sigfillset(&all_sigs); + result = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs); + if(result == -1) { + PERROR("sigprocmask"); + return; + } +} + +/* Don't call this function directly in a traced program */ +static void ust_after_fork_common(ust_fork_info_t *fork_info) +{ + int result; + sigset_t orig_sigs; + + /* Restore signals */ + result = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL); + if(result == -1) { + PERROR("sigprocmask"); + return; + } +} + +void ust_after_fork_parent(ust_fork_info_t *fork_info) +{ + /* Reenable signals */ + ust_after_fork_common(fork_info); +} + +void ust_after_fork_child(ust_fork_info_t *fork_info) +{ + /* First sanitize the child */ + ust_fork(); + + /* Then reenable interrupts */ + ust_after_fork_common(fork_info); +} +