Implement bpf_send_signal_remote kfunc that is similar to
bpf_send_signal_thread and bpf_send_signal helpers but can be used to
send signals to other threads and processes. It also supports sending a
cookie with the signal similar to sigqueue().
If the receiving process establishes a handler for the signal using the
SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
si_value field of the siginfo_t structure passed as the second argument
to the handler.
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 77 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a582cd25ca876..51b27db1321fc 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -802,6 +802,9 @@ struct send_signal_irq_work {
struct task_struct *task;
u32 sig;
enum pid_type type;
+ bool is_siginfo;
+ kernel_siginfo_t info;
+ int value;
};
static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
@@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
struct send_signal_irq_work *work;
work = container_of(entry, struct send_signal_irq_work, irq_work);
- group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
+ if (work->is_siginfo)
+ group_send_sig_info(work->sig, &work->info, work->task, work->type);
+ else
+ group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
+
put_task_struct(work->task);
}
@@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
* irq works get executed.
*/
work->task = get_task_struct(current);
+ work->is_siginfo = false;
work->sig = sig;
work->type = type;
irq_work_queue(&work->irq_work);
@@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
}
late_initcall(bpf_kprobe_multi_kfuncs_init);
+
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
+ int value)
+{
+ struct send_signal_irq_work *work = NULL;
+ kernel_siginfo_t info;
+
+ if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
+ return -EINVAL;
+ if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
+ return -EPERM;
+ if (unlikely(!nmi_uaccess_okay()))
+ return -EPERM;
+ /* Task should not be pid=1 to avoid kernel panic. */
+ if (unlikely(is_global_init(task)))
+ return -EPERM;
+
+ clear_siginfo(&info);
+ info.si_signo = sig;
+ info.si_errno = 0;
+ info.si_code = SI_KERNEL;
+ info.si_pid = 0;
+ info.si_uid = 0;
+ info.si_value.sival_int = value;
+
+ if (irqs_disabled()) {
+ /* Do an early check on signal validity. Otherwise,
+ * the error is lost in deferred irq_work.
+ */
+ if (unlikely(!valid_signal(sig)))
+ return -EINVAL;
+
+ work = this_cpu_ptr(&send_signal_work);
+ if (irq_work_is_busy(&work->irq_work))
+ return -EBUSY;
+
+ work->task = get_task_struct(task);
+ work->is_siginfo = true;
+ work->info = info;
+ work->sig = sig;
+ work->type = type;
+ work->value = value;
+ irq_work_queue(&work->irq_work);
+ return 0;
+ }
+
+ return group_send_sig_info(sig, &info, task, type);
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(send_signal_kfunc_ids)
+BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
+BTF_KFUNCS_END(send_signal_kfunc_ids)
+
+static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &send_signal_kfunc_ids,
+};
+
+static int __init bpf_send_signal_kfuncs_init(void)
+{
+ return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
+}
+
+late_initcall(bpf_send_signal_kfuncs_init);
--
2.40.1On Thu, Sep 26, 2024 at 4:53 AM Puranjay Mohan <puranjay@kernel.org> wrote:
>
> Implement bpf_send_signal_remote kfunc that is similar to
> bpf_send_signal_thread and bpf_send_signal helpers but can be used to
> send signals to other threads and processes. It also supports sending a
> cookie with the signal similar to sigqueue().
>
> If the receiving process establishes a handler for the signal using the
> SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
> si_value field of the siginfo_t structure passed as the second argument
> to the handler.
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
> kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index a582cd25ca876..51b27db1321fc 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -802,6 +802,9 @@ struct send_signal_irq_work {
> struct task_struct *task;
> u32 sig;
> enum pid_type type;
> + bool is_siginfo;
> + kernel_siginfo_t info;
> + int value;
> };
>
> static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
> @@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
> struct send_signal_irq_work *work;
>
> work = container_of(entry, struct send_signal_irq_work, irq_work);
> - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> + if (work->is_siginfo)
> + group_send_sig_info(work->sig, &work->info, work->task, work->type);
> + else
> + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> +
> put_task_struct(work->task);
> }
>
> @@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
> * irq works get executed.
> */
> work->task = get_task_struct(current);
> + work->is_siginfo = false;
> work->sig = sig;
> work->type = type;
> irq_work_queue(&work->irq_work);
> @@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
> }
>
> late_initcall(bpf_kprobe_multi_kfuncs_init);
> +
> +__bpf_kfunc_start_defs();
> +
> +__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
> + int value)
> +{
> + struct send_signal_irq_work *work = NULL;
> + kernel_siginfo_t info;
> +
> + if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
> + return -EINVAL;
> + if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
> + return -EPERM;
> + if (unlikely(!nmi_uaccess_okay()))
> + return -EPERM;
> + /* Task should not be pid=1 to avoid kernel panic. */
> + if (unlikely(is_global_init(task)))
> + return -EPERM;
> +
> + clear_siginfo(&info);
> + info.si_signo = sig;
> + info.si_errno = 0;
> + info.si_code = SI_KERNEL;
> + info.si_pid = 0;
> + info.si_uid = 0;
> + info.si_value.sival_int = value;
It seems like it could be either int sival_int or `void *sival_ptr`,
i.e., it's actually a 64-bit value on 64-bit architectures.
Can we allow passing a full u64 here and assign it to sival_ptr (with a cast)?
> +
> + if (irqs_disabled()) {
> + /* Do an early check on signal validity. Otherwise,
> + * the error is lost in deferred irq_work.
> + */
> + if (unlikely(!valid_signal(sig)))
> + return -EINVAL;
> +
> + work = this_cpu_ptr(&send_signal_work);
> + if (irq_work_is_busy(&work->irq_work))
> + return -EBUSY;
> +
> + work->task = get_task_struct(task);
> + work->is_siginfo = true;
> + work->info = info;
> + work->sig = sig;
> + work->type = type;
> + work->value = value;
> + irq_work_queue(&work->irq_work);
> + return 0;
> + }
> +
> + return group_send_sig_info(sig, &info, task, type);
> +}
> +
> +__bpf_kfunc_end_defs();
> +
> +BTF_KFUNCS_START(send_signal_kfunc_ids)
> +BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
> +BTF_KFUNCS_END(send_signal_kfunc_ids)
> +
> +static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &send_signal_kfunc_ids,
> +};
> +
> +static int __init bpf_send_signal_kfuncs_init(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
let's allow it for other program types (at least kprobes, tracepoints,
raw_tp, etc, etc)? Is there any problem just allowing it for any
program type?
> +}
> +
> +late_initcall(bpf_send_signal_kfuncs_init);
> --
> 2.40.1
>
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Thu, Sep 26, 2024 at 4:53 AM Puranjay Mohan <puranjay@kernel.org> wrote:
>>
>> Implement bpf_send_signal_remote kfunc that is similar to
>> bpf_send_signal_thread and bpf_send_signal helpers but can be used to
>> send signals to other threads and processes. It also supports sending a
>> cookie with the signal similar to sigqueue().
>>
>> If the receiving process establishes a handler for the signal using the
>> SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
>> si_value field of the siginfo_t structure passed as the second argument
>> to the handler.
>>
>> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
>> ---
>> kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 77 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index a582cd25ca876..51b27db1321fc 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -802,6 +802,9 @@ struct send_signal_irq_work {
>> struct task_struct *task;
>> u32 sig;
>> enum pid_type type;
>> + bool is_siginfo;
>> + kernel_siginfo_t info;
>> + int value;
>> };
>>
>> static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
>> @@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
>> struct send_signal_irq_work *work;
>>
>> work = container_of(entry, struct send_signal_irq_work, irq_work);
>> - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
>> + if (work->is_siginfo)
>> + group_send_sig_info(work->sig, &work->info, work->task, work->type);
>> + else
>> + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
>> +
>> put_task_struct(work->task);
>> }
>>
>> @@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
>> * irq works get executed.
>> */
>> work->task = get_task_struct(current);
>> + work->is_siginfo = false;
>> work->sig = sig;
>> work->type = type;
>> irq_work_queue(&work->irq_work);
>> @@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
>> }
>>
>> late_initcall(bpf_kprobe_multi_kfuncs_init);
>> +
>> +__bpf_kfunc_start_defs();
>> +
>> +__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
>> + int value)
>> +{
>> + struct send_signal_irq_work *work = NULL;
>> + kernel_siginfo_t info;
>> +
>> + if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
>> + return -EINVAL;
>> + if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
>> + return -EPERM;
>> + if (unlikely(!nmi_uaccess_okay()))
>> + return -EPERM;
>> + /* Task should not be pid=1 to avoid kernel panic. */
>> + if (unlikely(is_global_init(task)))
>> + return -EPERM;
>> +
>> + clear_siginfo(&info);
>> + info.si_signo = sig;
>> + info.si_errno = 0;
>> + info.si_code = SI_KERNEL;
>> + info.si_pid = 0;
>> + info.si_uid = 0;
>> + info.si_value.sival_int = value;
>
> It seems like it could be either int sival_int or `void *sival_ptr`,
> i.e., it's actually a 64-bit value on 64-bit architectures.
>
> Can we allow passing a full u64 here and assign it to sival_ptr (with a cast)?
Yes, I initially thought of allowing the kfunc to take the union itself
but turns out unions are not supported, so I will just use a cast to put
the value in sival_ptr.
>> +
>> + if (irqs_disabled()) {
>> + /* Do an early check on signal validity. Otherwise,
>> + * the error is lost in deferred irq_work.
>> + */
>> + if (unlikely(!valid_signal(sig)))
>> + return -EINVAL;
>> +
>> + work = this_cpu_ptr(&send_signal_work);
>> + if (irq_work_is_busy(&work->irq_work))
>> + return -EBUSY;
>> +
>> + work->task = get_task_struct(task);
>> + work->is_siginfo = true;
>> + work->info = info;
>> + work->sig = sig;
>> + work->type = type;
>> + work->value = value;
>> + irq_work_queue(&work->irq_work);
>> + return 0;
>> + }
>> +
>> + return group_send_sig_info(sig, &info, task, type);
>> +}
>> +
>> +__bpf_kfunc_end_defs();
>> +
>> +BTF_KFUNCS_START(send_signal_kfunc_ids)
>> +BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
>> +BTF_KFUNCS_END(send_signal_kfunc_ids)
>> +
>> +static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
>> + .owner = THIS_MODULE,
>> + .set = &send_signal_kfunc_ids,
>> +};
>> +
>> +static int __init bpf_send_signal_kfuncs_init(void)
>> +{
>> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
>
> let's allow it for other program types (at least kprobes, tracepoints,
> raw_tp, etc, etc)? Is there any problem just allowing it for any
> program type?
I guess we can allow it for all program types.
>
>> +}
>> +
>> +late_initcall(bpf_send_signal_kfuncs_init);
>> --
>> 2.40.1
>>
On Mon, Sep 30, 2024 at 2:48 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Thu, Sep 26, 2024 at 4:53 AM Puranjay Mohan <puranjay@kernel.org> wrote:
> >
> > Implement bpf_send_signal_remote kfunc that is similar to
> > bpf_send_signal_thread and bpf_send_signal helpers but can be used to
> > send signals to other threads and processes. It also supports sending a
> > cookie with the signal similar to sigqueue().
> >
> > If the receiving process establishes a handler for the signal using the
> > SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
> > si_value field of the siginfo_t structure passed as the second argument
> > to the handler.
> >
> > Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> > ---
> > kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 77 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index a582cd25ca876..51b27db1321fc 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -802,6 +802,9 @@ struct send_signal_irq_work {
> > struct task_struct *task;
> > u32 sig;
> > enum pid_type type;
> > + bool is_siginfo;
> > + kernel_siginfo_t info;
> > + int value;
> > };
> >
> > static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
> > @@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
> > struct send_signal_irq_work *work;
> >
> > work = container_of(entry, struct send_signal_irq_work, irq_work);
> > - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> > + if (work->is_siginfo)
> > + group_send_sig_info(work->sig, &work->info, work->task, work->type);
> > + else
> > + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> > +
> > put_task_struct(work->task);
> > }
> >
> > @@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
> > * irq works get executed.
> > */
> > work->task = get_task_struct(current);
> > + work->is_siginfo = false;
> > work->sig = sig;
> > work->type = type;
> > irq_work_queue(&work->irq_work);
> > @@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
> > }
> >
> > late_initcall(bpf_kprobe_multi_kfuncs_init);
> > +
> > +__bpf_kfunc_start_defs();
> > +
> > +__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
> > + int value)
Bikeshedding here a bit, but would bpf_send_signal_task() be a better
name for something that accepts task_struct?
> > +{
> > + struct send_signal_irq_work *work = NULL;
> > + kernel_siginfo_t info;
> > +
> > + if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
> > + return -EINVAL;
> > + if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
> > + return -EPERM;
> > + if (unlikely(!nmi_uaccess_okay()))
> > + return -EPERM;
> > + /* Task should not be pid=1 to avoid kernel panic. */
> > + if (unlikely(is_global_init(task)))
> > + return -EPERM;
> > +
> > + clear_siginfo(&info);
> > + info.si_signo = sig;
> > + info.si_errno = 0;
> > + info.si_code = SI_KERNEL;
> > + info.si_pid = 0;
> > + info.si_uid = 0;
> > + info.si_value.sival_int = value;
>
> It seems like it could be either int sival_int or `void *sival_ptr`,
> i.e., it's actually a 64-bit value on 64-bit architectures.
>
> Can we allow passing a full u64 here and assign it to sival_ptr (with a cast)?
Seems like Alexei already suggested that on patch #2, I support the request.
>
> > +
> > + if (irqs_disabled()) {
> > + /* Do an early check on signal validity. Otherwise,
> > + * the error is lost in deferred irq_work.
> > + */
> > + if (unlikely(!valid_signal(sig)))
> > + return -EINVAL;
> > +
> > + work = this_cpu_ptr(&send_signal_work);
> > + if (irq_work_is_busy(&work->irq_work))
> > + return -EBUSY;
> > +
> > + work->task = get_task_struct(task);
> > + work->is_siginfo = true;
> > + work->info = info;
> > + work->sig = sig;
> > + work->type = type;
> > + work->value = value;
> > + irq_work_queue(&work->irq_work);
> > + return 0;
> > + }
> > +
> > + return group_send_sig_info(sig, &info, task, type);
> > +}
> > +
> > +__bpf_kfunc_end_defs();
> > +
> > +BTF_KFUNCS_START(send_signal_kfunc_ids)
> > +BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
> > +BTF_KFUNCS_END(send_signal_kfunc_ids)
> > +
> > +static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
> > + .owner = THIS_MODULE,
> > + .set = &send_signal_kfunc_ids,
> > +};
> > +
> > +static int __init bpf_send_signal_kfuncs_init(void)
> > +{
> > + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
>
> let's allow it for other program types (at least kprobes, tracepoints,
> raw_tp, etc, etc)? Is there any problem just allowing it for any
> program type?
>
>
> > +}
> > +
> > +late_initcall(bpf_send_signal_kfuncs_init);
> > --
> > 2.40.1
> >
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Mon, Sep 30, 2024 at 2:48 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
>>
>> On Thu, Sep 26, 2024 at 4:53 AM Puranjay Mohan <puranjay@kernel.org> wrote:
>> >
>> > Implement bpf_send_signal_remote kfunc that is similar to
>> > bpf_send_signal_thread and bpf_send_signal helpers but can be used to
>> > send signals to other threads and processes. It also supports sending a
>> > cookie with the signal similar to sigqueue().
>> >
>> > If the receiving process establishes a handler for the signal using the
>> > SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
>> > si_value field of the siginfo_t structure passed as the second argument
>> > to the handler.
>> >
>> > Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
>> > ---
>> > kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
>> > 1 file changed, 77 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> > index a582cd25ca876..51b27db1321fc 100644
>> > --- a/kernel/trace/bpf_trace.c
>> > +++ b/kernel/trace/bpf_trace.c
>> > @@ -802,6 +802,9 @@ struct send_signal_irq_work {
>> > struct task_struct *task;
>> > u32 sig;
>> > enum pid_type type;
>> > + bool is_siginfo;
>> > + kernel_siginfo_t info;
>> > + int value;
>> > };
>> >
>> > static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
>> > @@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
>> > struct send_signal_irq_work *work;
>> >
>> > work = container_of(entry, struct send_signal_irq_work, irq_work);
>> > - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
>> > + if (work->is_siginfo)
>> > + group_send_sig_info(work->sig, &work->info, work->task, work->type);
>> > + else
>> > + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
>> > +
>> > put_task_struct(work->task);
>> > }
>> >
>> > @@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
>> > * irq works get executed.
>> > */
>> > work->task = get_task_struct(current);
>> > + work->is_siginfo = false;
>> > work->sig = sig;
>> > work->type = type;
>> > irq_work_queue(&work->irq_work);
>> > @@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
>> > }
>> >
>> > late_initcall(bpf_kprobe_multi_kfuncs_init);
>> > +
>> > +__bpf_kfunc_start_defs();
>> > +
>> > +__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
>> > + int value)
>
> Bikeshedding here a bit, but would bpf_send_signal_task() be a better
> name for something that accepts task_struct?
I agree, will use that name in the next version.
>> > +{
>> > + struct send_signal_irq_work *work = NULL;
>> > + kernel_siginfo_t info;
>> > +
>> > + if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
>> > + return -EINVAL;
>> > + if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
>> > + return -EPERM;
>> > + if (unlikely(!nmi_uaccess_okay()))
>> > + return -EPERM;
>> > + /* Task should not be pid=1 to avoid kernel panic. */
>> > + if (unlikely(is_global_init(task)))
>> > + return -EPERM;
>> > +
>> > + clear_siginfo(&info);
>> > + info.si_signo = sig;
>> > + info.si_errno = 0;
>> > + info.si_code = SI_KERNEL;
>> > + info.si_pid = 0;
>> > + info.si_uid = 0;
>> > + info.si_value.sival_int = value;
>>
>> It seems like it could be either int sival_int or `void *sival_ptr`,
>> i.e., it's actually a 64-bit value on 64-bit architectures.
>>
>> Can we allow passing a full u64 here and assign it to sival_ptr (with a cast)?
>
> Seems like Alexei already suggested that on patch #2, I support the request.
>
>>
>> > +
>> > + if (irqs_disabled()) {
>> > + /* Do an early check on signal validity. Otherwise,
>> > + * the error is lost in deferred irq_work.
>> > + */
>> > + if (unlikely(!valid_signal(sig)))
>> > + return -EINVAL;
>> > +
>> > + work = this_cpu_ptr(&send_signal_work);
>> > + if (irq_work_is_busy(&work->irq_work))
>> > + return -EBUSY;
>> > +
>> > + work->task = get_task_struct(task);
>> > + work->is_siginfo = true;
>> > + work->info = info;
>> > + work->sig = sig;
>> > + work->type = type;
>> > + work->value = value;
>> > + irq_work_queue(&work->irq_work);
>> > + return 0;
>> > + }
>> > +
>> > + return group_send_sig_info(sig, &info, task, type);
>> > +}
>> > +
>> > +__bpf_kfunc_end_defs();
>> > +
>> > +BTF_KFUNCS_START(send_signal_kfunc_ids)
>> > +BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
>> > +BTF_KFUNCS_END(send_signal_kfunc_ids)
>> > +
>> > +static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
>> > + .owner = THIS_MODULE,
>> > + .set = &send_signal_kfunc_ids,
>> > +};
>> > +
>> > +static int __init bpf_send_signal_kfuncs_init(void)
>> > +{
>> > + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
>>
>> let's allow it for other program types (at least kprobes, tracepoints,
>> raw_tp, etc, etc)? Is there any problem just allowing it for any
>> program type?
>>
>>
>> > +}
>> > +
>> > +late_initcall(bpf_send_signal_kfuncs_init);
>> > --
>> > 2.40.1
>> >
On Thu, Sep 26, 2024 at 4:53 AM Puranjay Mohan <puranjay@kernel.org> wrote:
>
> Implement bpf_send_signal_remote kfunc that is similar to
> bpf_send_signal_thread and bpf_send_signal helpers but can be used to
> send signals to other threads and processes. It also supports sending a
> cookie with the signal similar to sigqueue().
>
> If the receiving process establishes a handler for the signal using the
> SA_SIGINFO flag to sigaction(), then it can obtain this cookie via the
> si_value field of the siginfo_t structure passed as the second argument
> to the handler.
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
> kernel/trace/bpf_trace.c | 78 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index a582cd25ca876..51b27db1321fc 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -802,6 +802,9 @@ struct send_signal_irq_work {
> struct task_struct *task;
> u32 sig;
> enum pid_type type;
> + bool is_siginfo;
> + kernel_siginfo_t info;
> + int value;
> };
>
> static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work);
> @@ -811,7 +814,11 @@ static void do_bpf_send_signal(struct irq_work *entry)
> struct send_signal_irq_work *work;
>
> work = container_of(entry, struct send_signal_irq_work, irq_work);
> - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> + if (work->is_siginfo)
> + group_send_sig_info(work->sig, &work->info, work->task, work->type);
> + else
> + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type);
> +
> put_task_struct(work->task);
> }
>
> @@ -848,6 +855,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
> * irq works get executed.
> */
> work->task = get_task_struct(current);
> + work->is_siginfo = false;
> work->sig = sig;
> work->type = type;
> irq_work_queue(&work->irq_work);
> @@ -3484,3 +3492,71 @@ static int __init bpf_kprobe_multi_kfuncs_init(void)
> }
>
> late_initcall(bpf_kprobe_multi_kfuncs_init);
> +
> +__bpf_kfunc_start_defs();
> +
> +__bpf_kfunc int bpf_send_signal_remote(struct task_struct *task, int sig, enum pid_type type,
> + int value)
> +{
> + struct send_signal_irq_work *work = NULL;
> + kernel_siginfo_t info;
> +
> + if (type != PIDTYPE_PID && type != PIDTYPE_TGID)
> + return -EINVAL;
> + if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING)))
> + return -EPERM;
> + if (unlikely(!nmi_uaccess_okay()))
> + return -EPERM;
> + /* Task should not be pid=1 to avoid kernel panic. */
> + if (unlikely(is_global_init(task)))
> + return -EPERM;
> +
> + clear_siginfo(&info);
> + info.si_signo = sig;
> + info.si_errno = 0;
> + info.si_code = SI_KERNEL;
> + info.si_pid = 0;
> + info.si_uid = 0;
> + info.si_value.sival_int = value;
> +
> + if (irqs_disabled()) {
> + /* Do an early check on signal validity. Otherwise,
> + * the error is lost in deferred irq_work.
> + */
> + if (unlikely(!valid_signal(sig)))
> + return -EINVAL;
> +
> + work = this_cpu_ptr(&send_signal_work);
> + if (irq_work_is_busy(&work->irq_work))
> + return -EBUSY;
> +
> + work->task = get_task_struct(task);
> + work->is_siginfo = true;
> + work->info = info;
> + work->sig = sig;
> + work->type = type;
> + work->value = value;
> + irq_work_queue(&work->irq_work);
> + return 0;
> + }
> +
> + return group_send_sig_info(sig, &info, task, type);
This is very similar with bpf_send_signal_common().
Pls avoid copy paste and share the code instead.
> +}
> +
> +__bpf_kfunc_end_defs();
> +
> +BTF_KFUNCS_START(send_signal_kfunc_ids)
> +BTF_ID_FLAGS(func, bpf_send_signal_remote, KF_TRUSTED_ARGS)
> +BTF_KFUNCS_END(send_signal_kfunc_ids)
> +
> +static const struct btf_kfunc_id_set bpf_send_signal_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &send_signal_kfunc_ids,
> +};
> +
> +static int __init bpf_send_signal_kfuncs_init(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_send_signal_kfunc_set);
> +}
> +
> +late_initcall(bpf_send_signal_kfuncs_init);
Let's avoid all this later_init proliferation.
We have way too many of them across the whole kernel.
Reuse one of the existing places and add kfunc there.
With that extra bpf_send_signal_kfunc_set and send_signal_kfunc_ids
won't be necessary.
pw-bot: cr
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