| Message ID | 20230824103734.53453-2-flaniel@linux.microsoft.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Return EADDRNOTAVAIL when func matches several symbols during kprobe creation | expand |
On Thu, 24 Aug 2023 12:37:34 +0200 Francis Laniel <flaniel@linux.microsoft.com> wrote: > Previously to this commit, if func matches several symbols, a kprobe, being > either sysfs or PMU, would only be installed for the first matching address. > This could lead to some misunderstanding when some BPF code was never called > because it was attached to a function which was indeed not call, because the > effectively called one has no kprobes. > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > This way, user needs to use addr to remove the ambiguity. Thanks for update the patch. I have some comments there. > > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ > --- > kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 23dba01831f7..0c8dd6ba650b 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = { > .priority = 1 /* Invoked after kprobe module callback */ > }; > > +static int count_symbols(void *data, unsigned long unused) > +{ > + unsigned int *count = data; > + > + (*count)++; > + > + return 0; > +} > + > +static unsigned int func_name_several_symbols(char *func_name) If this returns boolean, please use 'bool' for return type. Also, I think 'func_name_is_unique()' is more natural. > +{ > + unsigned int count; > + > + count = 0; > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > + > + return count > 1; > +} > + > static int __trace_kprobe_create(int argc, const char *argv[]) > { > /* > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char *argv[]) > } > } > > + /* > + * If user specifies KSYM, we check it does not correspond to several > + * symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > + */ > + if (symbol && func_name_several_symbols(symbol)) { Then, here will be if (symbol && !func_name_is_unique(symbol)) { > + ret = -EADDRNOTAVAIL; > + > + goto error; > + } > + > trace_probe_log_set_index(0); > if (event) { > ret = traceprobe_parse_event_name(&event, &group, gbuf, > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) > } > > #ifdef CONFIG_PERF_EVENTS > + > /* create a trace_kprobe, but don't add it to global lists */ > struct trace_event_call * > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > int ret; > char *event; > > + /* > + * If user specifies func, we check that function name does not > + * correspond to several symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use addr and offs rather than func to remove the > + * ambiguity. > + */ > + if (func && func_name_several_symbols(func)) Ditto. Thanks! > + return ERR_PTR(-EADDRNOTAVAIL); > + > /* > * local trace_kprobes are not added to dyn_event, so they are never > * searched in find_trace_kprobe(). Therefore, there is no concern of > -- > 2.34.1 >
Hi. Le jeudi 24 août 2023, 15:02:27 CEST Masami Hiramatsu a écrit : > On Thu, 24 Aug 2023 12:37:34 +0200 > > Francis Laniel <flaniel@linux.microsoft.com> wrote: > > Previously to this commit, if func matches several symbols, a kprobe, > > being > > either sysfs or PMU, would only be installed for the first matching > > address. This could lead to some misunderstanding when some BPF code was > > never called because it was attached to a function which was indeed not > > call, because the effectively called one has no kprobes. > > > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > > This way, user needs to use addr to remove the ambiguity. > > Thanks for update the patch. I have some comments there. > > > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > > Link: > > https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kern > > el.org/ --- > > > > kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ > > 1 file changed, 42 insertions(+) > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index 23dba01831f7..0c8dd6ba650b 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = > > {> > > .priority = 1 /* Invoked after kprobe module callback */ > > > > }; > > > > +static int count_symbols(void *data, unsigned long unused) > > +{ > > + unsigned int *count = data; > > + > > + (*count)++; > > + > > + return 0; > > +} > > + > > +static unsigned int func_name_several_symbols(char *func_name) > > If this returns boolean, please use 'bool' for return type. > Also, I think 'func_name_is_unique()' is more natural. > This name sounds better but it means it will check count == 1. I am fine with it, but please see my below comment. > > +{ > > + unsigned int count; > > + > > + count = 0; > > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > > + > > + return count > 1; > > +} > > + > > > > static int __trace_kprobe_create(int argc, const char *argv[]) > > { > > > > /* > > > > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char > > *argv[])> > > } > > > > } > > > > + /* > > + * If user specifies KSYM, we check it does not correspond to several > > + * symbols. > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > > + */ > > + if (symbol && func_name_several_symbols(symbol)) { > > Then, here will be > > if (symbol && !func_name_is_unique(symbol)) { > I am fine with the above, but it means if users gives an unknown symbol, we will return EADDRNOTAVAIL instead of currently returning ENOENT. Is it OK? > > + ret = -EADDRNOTAVAIL; > > + > > + goto error; > > + } > > + > > > > trace_probe_log_set_index(0); > > if (event) { > > > > ret = traceprobe_parse_event_name(&event, &group, gbuf, > > > > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct > > trace_kprobe *tk)> > > } > > > > #ifdef CONFIG_PERF_EVENTS > > > > + > > > > /* create a trace_kprobe, but don't add it to global lists */ > > struct trace_event_call * > > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > > > > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, > > unsigned long offs,> > > int ret; > > char *event; > > > > + /* > > + * If user specifies func, we check that function name does not > > + * correspond to several symbols. > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > + * he/she should use addr and offs rather than func to remove the > > + * ambiguity. > > + */ > > + if (func && func_name_several_symbols(func)) > > Ditto. > > Thanks! > > > + return ERR_PTR(-EADDRNOTAVAIL); > > + > > > > /* > > > > * local trace_kprobes are not added to dyn_event, so they are never > > * searched in find_trace_kprobe(). Therefore, there is no concern of Best regards.
On Thu, 24 Aug 2023 16:31:13 +0200 Francis Laniel <flaniel@linux.microsoft.com> wrote: > Hi. > > Le jeudi 24 août 2023, 15:02:27 CEST Masami Hiramatsu a écrit : > > On Thu, 24 Aug 2023 12:37:34 +0200 > > > > Francis Laniel <flaniel@linux.microsoft.com> wrote: > > > Previously to this commit, if func matches several symbols, a kprobe, > > > being > > > either sysfs or PMU, would only be installed for the first matching > > > address. This could lead to some misunderstanding when some BPF code was > > > never called because it was attached to a function which was indeed not > > > call, because the effectively called one has no kprobes. > > > > > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > > > This way, user needs to use addr to remove the ambiguity. > > > > Thanks for update the patch. I have some comments there. > > > > > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > > > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > > > Link: > > > https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kern > > > el.org/ --- > > > > > > kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 42 insertions(+) > > > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > > index 23dba01831f7..0c8dd6ba650b 100644 > > > --- a/kernel/trace/trace_kprobe.c > > > +++ b/kernel/trace/trace_kprobe.c > > > @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = > > > {> > > > .priority = 1 /* Invoked after kprobe module callback */ > > > > > > }; > > > > > > +static int count_symbols(void *data, unsigned long unused) > > > +{ > > > + unsigned int *count = data; > > > + > > > + (*count)++; > > > + > > > + return 0; > > > +} > > > + > > > +static unsigned int func_name_several_symbols(char *func_name) > > > > If this returns boolean, please use 'bool' for return type. > > Also, I think 'func_name_is_unique()' is more natural. > > > > This name sounds better but it means it will check count == 1. > I am fine with it, but please see my below comment. > > > > +{ > > > + unsigned int count; > > > + > > > + count = 0; > > > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > > > + > > > + return count > 1; > > > +} > > > + > > > > > > static int __trace_kprobe_create(int argc, const char *argv[]) > > > { > > > > > > /* > > > > > > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char > > > *argv[])> > > > } > > > > > > } > > > > > > + /* > > > + * If user specifies KSYM, we check it does not correspond to several > > > + * symbols. > > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > > > + */ > > > + if (symbol && func_name_several_symbols(symbol)) { > > > > Then, here will be > > > > if (symbol && !func_name_is_unique(symbol)) { > > > > I am fine with the above, but it means if users gives an unknown symbol, we > will return EADDRNOTAVAIL instead of currently returning ENOENT. > Is it OK? Ah, good catch! Hm, then what about 'int number_of_same_symbols()' ? if (symbol) { num = number_of_same_symbols(symbol); if (num > 1) return -EADDRNOTAVAIL; else if (num == 0) return -ENOENT; } Thank you, > > > > + ret = -EADDRNOTAVAIL; > > > + > > > + goto error; > > > + } > > > + > > > > > > trace_probe_log_set_index(0); > > > if (event) { > > > > > > ret = traceprobe_parse_event_name(&event, &group, gbuf, > > > > > > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct > > > trace_kprobe *tk)> > > > } > > > > > > #ifdef CONFIG_PERF_EVENTS > > > > > > + > > > > > > /* create a trace_kprobe, but don't add it to global lists */ > > > struct trace_event_call * > > > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > > > > > > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, > > > unsigned long offs,> > > > int ret; > > > char *event; > > > > > > + /* > > > + * If user specifies func, we check that function name does not > > > + * correspond to several symbols. > > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > > + * he/she should use addr and offs rather than func to remove the > > > + * ambiguity. > > > + */ > > > + if (func && func_name_several_symbols(func)) > > > > Ditto. > > > > Thanks! > > > > > + return ERR_PTR(-EADDRNOTAVAIL); > > > + > > > > > > /* > > > > > > * local trace_kprobes are not added to dyn_event, so they are never > > > * searched in find_trace_kprobe(). Therefore, there is no concern of > > Best regards. > >
Le jeudi 24 août 2023, 16:47:21 CEST Masami Hiramatsu a écrit : > On Thu, 24 Aug 2023 16:31:13 +0200 > > Francis Laniel <flaniel@linux.microsoft.com> wrote: > > Hi. > > > > Le jeudi 24 août 2023, 15:02:27 CEST Masami Hiramatsu a écrit : > > > On Thu, 24 Aug 2023 12:37:34 +0200 > > > > > > Francis Laniel <flaniel@linux.microsoft.com> wrote: > > > > Previously to this commit, if func matches several symbols, a kprobe, > > > > being > > > > either sysfs or PMU, would only be installed for the first matching > > > > address. This could lead to some misunderstanding when some BPF code > > > > was > > > > never called because it was attached to a function which was indeed > > > > not > > > > call, because the effectively called one has no kprobes. > > > > > > > > So, this commit returns EADDRNOTAVAIL when func matches several > > > > symbols. > > > > This way, user needs to use addr to remove the ambiguity. > > > > > > Thanks for update the patch. I have some comments there. > > > > > > > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> > > > > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> > > > > Link: > > > > https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@k > > > > ern > > > > el.org/ --- > > > > > > > > kernel/trace/trace_kprobe.c | 42 > > > > +++++++++++++++++++++++++++++++++++++ > > > > 1 file changed, 42 insertions(+) > > > > > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > > > index 23dba01831f7..0c8dd6ba650b 100644 > > > > --- a/kernel/trace/trace_kprobe.c > > > > +++ b/kernel/trace/trace_kprobe.c > > > > @@ -705,6 +705,25 @@ static struct notifier_block > > > > trace_kprobe_module_nb = > > > > {> > > > > > > > > .priority = 1 /* Invoked after kprobe module callback */ > > > > > > > > }; > > > > > > > > +static int count_symbols(void *data, unsigned long unused) > > > > +{ > > > > + unsigned int *count = data; > > > > + > > > > + (*count)++; > > > > + > > > > + return 0; > > > > +} > > > > + > > > > +static unsigned int func_name_several_symbols(char *func_name) > > > > > > If this returns boolean, please use 'bool' for return type. > > > Also, I think 'func_name_is_unique()' is more natural. > > > > This name sounds better but it means it will check count == 1. > > I am fine with it, but please see my below comment. > > > > > > +{ > > > > + unsigned int count; > > > > + > > > > + count = 0; > > > > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > > > > + > > > > + return count > 1; > > > > +} > > > > + > > > > > > > > static int __trace_kprobe_create(int argc, const char *argv[]) > > > > { > > > > > > > > /* > > > > > > > > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const > > > > char > > > > *argv[])> > > > > > > > > } > > > > > > > > } > > > > > > > > + /* > > > > + * If user specifies KSYM, we check it does not correspond to > > > > several > > > > + * symbols. > > > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > > > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > > > > + */ > > > > + if (symbol && func_name_several_symbols(symbol)) { > > > > > > Then, here will be > > > > > > if (symbol && !func_name_is_unique(symbol)) { > > > > I am fine with the above, but it means if users gives an unknown symbol, > > we > > will return EADDRNOTAVAIL instead of currently returning ENOENT. > > Is it OK? > > Ah, good catch! Hm, then what about 'int number_of_same_symbols()' ? > > > if (symbol) { > num = number_of_same_symbols(symbol); > if (num > 1) > return -EADDRNOTAVAIL; > else if (num == 0) > return -ENOENT; > } Done in the v3 :D! > Thank you, > > > > > + ret = -EADDRNOTAVAIL; > > > > + > > > > + goto error; > > > > + } > > > > + > > > > > > > > trace_probe_log_set_index(0); > > > > if (event) { > > > > > > > > ret = traceprobe_parse_event_name(&event, &group, gbuf, > > > > > > > > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct > > > > trace_kprobe *tk)> > > > > > > > > } > > > > > > > > #ifdef CONFIG_PERF_EVENTS > > > > > > > > + > > > > > > > > /* create a trace_kprobe, but don't add it to global lists */ > > > > struct trace_event_call * > > > > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > > > > > > > > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void > > > > *addr, > > > > unsigned long offs,> > > > > > > > > int ret; > > > > char *event; > > > > > > > > + /* > > > > + * If user specifies func, we check that function name does not > > > > + * correspond to several symbols. > > > > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > > > > + * he/she should use addr and offs rather than func to remove the > > > > + * ambiguity. > > > > + */ > > > > + if (func && func_name_several_symbols(func)) > > > > > > Ditto. > > > > > > Thanks! > > > > > > > + return ERR_PTR(-EADDRNOTAVAIL); > > > > + > > > > > > > > /* > > > > > > > > * local trace_kprobes are not added to dyn_event, so they are never > > > > * searched in find_trace_kprobe(). Therefore, there is no concern > > > > of > > > > Best regards.
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 23dba01831f7..0c8dd6ba650b 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = { .priority = 1 /* Invoked after kprobe module callback */ }; +static int count_symbols(void *data, unsigned long unused) +{ + unsigned int *count = data; + + (*count)++; + + return 0; +} + +static unsigned int func_name_several_symbols(char *func_name) +{ + unsigned int count; + + count = 0; + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); + + return count > 1; +} + static int __trace_kprobe_create(int argc, const char *argv[]) { /* @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char *argv[]) } } + /* + * If user specifies KSYM, we check it does not correspond to several + * symbols. + * If this is the case, we return EADDRNOTAVAIL to indicate the user + * he/she should use ADDR rather than KSYM to remove the ambiguity. + */ + if (symbol && func_name_several_symbols(symbol)) { + ret = -EADDRNOTAVAIL; + + goto error; + } + trace_probe_log_set_index(0); if (event) { ret = traceprobe_parse_event_name(&event, &group, gbuf, @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) } #ifdef CONFIG_PERF_EVENTS + /* create a trace_kprobe, but don't add it to global lists */ struct trace_event_call * create_local_trace_kprobe(char *func, void *addr, unsigned long offs, @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, int ret; char *event; + /* + * If user specifies func, we check that function name does not + * correspond to several symbols. + * If this is the case, we return EADDRNOTAVAIL to indicate the user + * he/she should use addr and offs rather than func to remove the + * ambiguity. + */ + if (func && func_name_several_symbols(func)) + return ERR_PTR(-EADDRNOTAVAIL); + /* * local trace_kprobes are not added to dyn_event, so they are never * searched in find_trace_kprobe(). Therefore, there is no concern of
Previously to this commit, if func matches several symbols, a kprobe, being either sysfs or PMU, would only be installed for the first matching address. This could lead to some misunderstanding when some BPF code was never called because it was attached to a function which was indeed not call, because the effectively called one has no kprobes. So, this commit returns EADDRNOTAVAIL when func matches several symbols. This way, user needs to use addr to remove the ambiguity. Suggested-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com> Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ --- kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+)