IR decoding using BPF

drivers/media/rc/Kconfig +9 -0

+	depends on LIRC
+	help
+	   Allow attaching eBPF programs to a lirc device using the bpf(2)
+	   syscall command BPF_PROG_ATTACH. This is supported for raw IR
+	   receivers.
+
+	   These eBPF programs can be used to decode IR into scancodes, for
+	   IR protocols not supported by the kernel decoders.
+
 menuconfig RC_DECODERS
 	bool "Remote controller decoders"
 	depends on RC_CORE
[...]

kernel/bpf/syscall.c +5 -0

index 388d4feda348..3c104113d040 100644
@@ -11,6 +11,7 @@
  */
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
+#include <linux/bpf_lirc.h>
 #include <linux/btf.h>
 #include <linux/syscalls.h>
 #include <linux/slab.h>

@@ -1578,6 +1579,8 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
 		return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, true);
+	case BPF_LIRC_MODE2:
+		return lirc_prog_attach(attr);
 	default:
 		return -EINVAL;
 	}

@@ -1648,6 +1651,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
 		return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, false);
+	case BPF_LIRC_MODE2:
+		return lirc_prog_detach(attr);
 	default:
 		return -EINVAL;
 	}

kernel/bpf/syscall.c +0 -0

 	default:
 		return -EINVAL;
 	}

Signature · 1 line

2.17.0

Hi Sean,

I finally found the time to test your patch series and noticed 2 issues - comments are inline

drivers/media/rc/Kconfig config LIRC · line 31

Quoted 12 lines · Sean Young

drivers/media/rc/Kconfig +4 -0

index eb2c3b6eca7f..d5b35a6ba899 100644
@@ -25,6 +25,19 @@ config LIRC
 	   passes raw IR to and from userspace, which is needed for
 	   IR transmitting (aka "blasting") and for the lirc daemon.
 
+config BPF_LIRC_MODE2
+	bool "Support for eBPF programs attached to lirc devices"
+	depends on BPF_SYSCALL
+	depends on RC_CORE=y

Requiring rc-core to be built into the kernel could become problematic in the future for people using media_build.

Currently the whole media tree (including rc-core) can be built as modules so DVB and IR drivers can be replaced by newer versions. But with rc-core in the kernel things could easily break if internal data structures are changed.

Maybe we should add a small layer with a stable API/ABI between bpf-lirc and rc-core to decouple them? Or would it be possible to build rc-core with bpf support as a module?

Quoted 44 lines

drivers/media/rc/Kconfig +9 -0

+	depends on LIRC
+	help
+	   Allow attaching eBPF programs to a lirc device using the bpf(2)
+	   syscall command BPF_PROG_ATTACH. This is supported for raw IR
+	   receivers.
+
+	   These eBPF programs can be used to decode IR into scancodes, for
+	   IR protocols not supported by the kernel decoders.
+
 menuconfig RC_DECODERS
 	bool "Remote controller decoders"
 	depends on RC_CORE
[...]

kernel/bpf/syscall.c +5 -0

index 388d4feda348..3c104113d040 100644
@@ -11,6 +11,7 @@
  */
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
+#include <linux/bpf_lirc.h>
 #include <linux/btf.h>
 #include <linux/syscalls.h>
 #include <linux/slab.h>

@@ -1578,6 +1579,8 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
 		return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, true);
+	case BPF_LIRC_MODE2:
+		return lirc_prog_attach(attr);
 	default:
 		return -EINVAL;
 	}

@@ -1648,6 +1651,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 	case BPF_SK_SKB_STREAM_PARSER:
 	case BPF_SK_SKB_STREAM_VERDICT:
 		return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, false);
+	case BPF_LIRC_MODE2:
+		return lirc_prog_detach(attr);
 	default:
 		return -EINVAL;
 	}

kernel/bpf/syscall.c static int bpf_prog_query(const union bpf_attr *attr, · line 1704

Quoted 5 lines

kernel/bpf/syscall.c +2 -0

@@ -1695,6 +1700,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
 	case BPF_CGROUP_SOCK_OPS:
 	case BPF_CGROUP_DEVICE:
 		break;
+	case BPF_LIRC_MODE2:
+		return lirc_prog_query(attr, uattr);

When testing this patch series I was wondering why I always got -EINVAL when trying to query the registered programs.

Closer inspection revealed that bpf_prog_attach/detach/query and calls to them in the bpf syscall are in "#ifdef CONFIG_CGROUP_BPF" blocks - and as I built the kernel without CONFIG_CGROUP_BPF BPF_PROG_ATTACH/DETACH/QUERY weren't handled in the syscall switch and I got -EINVAL from the bpf syscall function.

I haven't checked in detail yet, but it looks to me like bpf_prog_attach/detach/query could always be built (or when either cgroup bpf or lirc bpf are enabled) and the #ifdefs moved inside the switch(). So lirc bpf could be used without cgroup bpf. Or am I missing something?

On Mon, Jun 04, 2018 at 07:47:30PM +0200, Matthias Reichl wrote:

Quoted 16 lines

kernel/bpf/syscall.c static int bpf_prog_query(const union bpf_attr *attr, · line 1704

Quoted 6 lines

kernel/bpf/syscall.c +2 -0

@@ -1695,6 +1700,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
 	case BPF_CGROUP_SOCK_OPS:
 	case BPF_CGROUP_DEVICE:
 		break;
+	case BPF_LIRC_MODE2:
+		return lirc_prog_query(attr, uattr);

When testing this patch series I was wondering why I always got -EINVAL when trying to query the registered programs.

Closer inspection revealed that bpf_prog_attach/detach/query and calls to them in the bpf syscall are in "#ifdef CONFIG_CGROUP_BPF" blocks - and as I built the kernel without CONFIG_CGROUP_BPF BPF_PROG_ATTACH/DETACH/QUERY weren't handled in the syscall switch and I got -EINVAL from the bpf syscall function.

Quoted 5 lines

I haven't checked in detail yet, but it looks to me like bpf_prog_attach/detach/query could always be built (or when either cgroup bpf or lirc bpf are enabled) and the #ifdefs moved inside the switch(). So lirc bpf could be used without cgroup bpf. Or am I missing something?

You are right, this features depends on CONFIG_CGROUP_BPF right now. This also affects the BPF_SK_MSG_VERDICT, BPF_SK_SKB_STREAM_VERDICT and BPF_SK_SKB_STREAM_PARSER type bpf attachments, and as far as I know these shouldn't depend on CONFIG_CGROUP_BPF either.

Compile bpf_prog_{attach,detach,query} even if CONFIG_BPF_CGROUP is not set.

Signed-off-by Sean Young <[email protected]>

Compile bpf_prog_{attach,detach,query} even if CONFIG_BPF_CGROUP is not set.

Signed-off-by Sean Young <[email protected]>

---
 include/linux/bpf-cgroup.h |  31 +++++++++++
 kernel/bpf/cgroup.c        | 110 +++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c       | 105 ++---------------------------------
 3 files changed, 145 insertions(+), 101 deletions(-)

include/linux/bpf-cgroup.h +31 -0

index 975fb4cf1bb7..ee67cd35f426 100644
@@ -188,12 +188,43 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
                                                                              \
        __ret;                                                                \
 })
+int sockmap_get_from_fd(const union bpf_attr *attr, int type, bool attach);
+int cgroup_bpf_prog_attach(const union bpf_attr *attr,
+                          enum bpf_prog_type ptype);
+int cgroup_bpf_prog_detach(const union bpf_attr *attr,
+                          enum bpf_prog_type ptype);
+int cgroup_bpf_prog_query(const union bpf_attr *attr,
+                         union bpf_attr __user *uattr);
 #else
 
 struct cgroup_bpf {};
 static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
 static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
 
+static inline int sockmap_get_from_fd(const union bpf_attr *attr,
+                                     int type, bool attach)
+{
+       return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_attach(const union bpf_attr *attr,
+                                        enum bpf_prog_type ptype)
+{
+       return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_detach(const union bpf_attr *attr,
+                                        enum bpf_prog_type ptype)
+{
+       return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
+                                       union bpf_attr __user *uattr)
+{
+       return -EINVAL;
+}
+
 #define cgroup_bpf_enabled (0)
 #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (0)
 #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })

kernel/bpf/cgroup.c +110 -0

index f7c00bd6f8e4..d6e18f9dc0c4 100644
@@ -428,6 +428,116 @@ int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
        return ret;
 }
 
+int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
+                                     enum bpf_attach_type attach_type)
+{
+       switch (prog->type) {
+       case BPF_PROG_TYPE_CGROUP_SOCK:
+       case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
+               return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
+       default:
+               return 0;
+       }
+}
+
+int sockmap_get_from_fd(const union bpf_attr *attr, int type, bool attach)
+{
+       struct bpf_prog *prog = NULL;
+       int ufd = attr->target_fd;
+       struct bpf_map *map;
+       struct fd f;
+       int err;
+
+       f = fdget(ufd);
+       map = __bpf_map_get(f);
+       if (IS_ERR(map))
+               return PTR_ERR(map);
+
+       if (attach) {
+               prog = bpf_prog_get_type(attr->attach_bpf_fd, type);
+               if (IS_ERR(prog)) {
+                       fdput(f);
+                       return PTR_ERR(prog);
+               }
+       }
+
+       err = sock_map_prog(map, prog, attr->attach_type);
+       if (err) {
+               fdput(f);
+               if (prog)
+                       bpf_prog_put(prog);
+               return err;
+       }
+
+       fdput(f);
+       return 0;
+}
+
+int cgroup_bpf_prog_attach(const union bpf_attr *attr, enum bpf_prog_type ptype)
+{
+       struct bpf_prog *prog;
+       struct cgroup *cgrp;
+       int ret;
+
+       prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
+       if (IS_ERR(prog))
+               return PTR_ERR(prog);
+
+       if (bpf_prog_attach_check_attach_type(prog, attr->attach_type)) {
+               bpf_prog_put(prog);
+               return -EINVAL;
+       }
+
+       cgrp = cgroup_get_from_fd(attr->target_fd);
+       if (IS_ERR(cgrp)) {
+               bpf_prog_put(prog);
+               return PTR_ERR(cgrp);
+       }
+
+       ret = cgroup_bpf_attach(cgrp, prog, attr->attach_type,
+                               attr->attach_flags);
+       if (ret)
+               bpf_prog_put(prog);
+       cgroup_put(cgrp);
+
+       return ret;
+}
+
+int cgroup_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
+{
+       struct bpf_prog *prog;
+       struct cgroup *cgrp;
+       int ret;
+
+       cgrp = cgroup_get_from_fd(attr->target_fd);
+       if (IS_ERR(cgrp))
+               return PTR_ERR(cgrp);
+
+       prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
+       if (IS_ERR(prog))
+               prog = NULL;
+
+       ret = cgroup_bpf_detach(cgrp, prog, attr->attach_type, 0);
+       if (prog)
+               bpf_prog_put(prog);
+       cgroup_put(cgrp);
+       return ret;
+}
+
+int cgroup_bpf_prog_query(const union bpf_attr *attr,
+                         union bpf_attr __user *uattr)
+{
+       struct cgroup *cgrp;
+       int ret;
+
+       cgrp = cgroup_get_from_fd(attr->query.target_fd);
+       if (IS_ERR(cgrp))
+               return PTR_ERR(cgrp);
+       ret = cgroup_bpf_query(cgrp, attr, uattr);
+       cgroup_put(cgrp);
+       return ret;
+}
+
 /**
  * __cgroup_bpf_run_filter_skb() - Run a program for packet filtering
  * @sk: The socket sending or receiving traffic

kernel/bpf/syscall.c +4 -102

index 0fa20624707f..52fa44856623 100644
@@ -1489,65 +1489,14 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
        return err;
 }
 
-#ifdef CONFIG_CGROUP_BPF
-
-static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
-                                            enum bpf_attach_type attach_type)
-{
-       switch (prog->type) {
-       case BPF_PROG_TYPE_CGROUP_SOCK:
-       case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
-               return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
-       default:
-               return 0;
-       }
-}
-
 #define BPF_PROG_ATTACH_LAST_FIELD attach_flags
 
-static int sockmap_get_from_fd(const union bpf_attr *attr,
-                              int type, bool attach)
-{
-       struct bpf_prog *prog = NULL;
-       int ufd = attr->target_fd;
-       struct bpf_map *map;
-       struct fd f;
-       int err;
-
-       f = fdget(ufd);
-       map = __bpf_map_get(f);
-       if (IS_ERR(map))
-               return PTR_ERR(map);
-
-       if (attach) {
-               prog = bpf_prog_get_type(attr->attach_bpf_fd, type);
-               if (IS_ERR(prog)) {
-                       fdput(f);
-                       return PTR_ERR(prog);
-               }
-       }
-
-       err = sock_map_prog(map, prog, attr->attach_type);
-       if (err) {
-               fdput(f);
-               if (prog)
-                       bpf_prog_put(prog);
-               return err;
-       }
-
-       fdput(f);
-       return 0;
-}
-
 #define BPF_F_ATTACH_MASK \
        (BPF_F_ALLOW_OVERRIDE | BPF_F_ALLOW_MULTI)
 
 static int bpf_prog_attach(const union bpf_attr *attr)
 {
        enum bpf_prog_type ptype;
-       struct bpf_prog *prog;
-       struct cgroup *cgrp;
-       int ret;
 
        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

@@ -1593,28 +1542,7 @@ static int bpf_prog_attach(const union bpf_attr *attr)
                return -EINVAL;
        }
 
-       prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
-       if (IS_ERR(prog))
-               return PTR_ERR(prog);
-
-       if (bpf_prog_attach_check_attach_type(prog, attr->attach_type)) {
-               bpf_prog_put(prog);
-               return -EINVAL;
-       }
-
-       cgrp = cgroup_get_from_fd(attr->target_fd);
-       if (IS_ERR(cgrp)) {
-               bpf_prog_put(prog);
-               return PTR_ERR(cgrp);
-       }
-
-       ret = cgroup_bpf_attach(cgrp, prog, attr->attach_type,
-                               attr->attach_flags);
-       if (ret)
-               bpf_prog_put(prog);
-       cgroup_put(cgrp);
-
-       return ret;
+       return cgroup_bpf_prog_attach(attr, ptype);
 }
 
 #define BPF_PROG_DETACH_LAST_FIELD attach_type

@@ -1622,9 +1550,6 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 static int bpf_prog_detach(const union bpf_attr *attr)
 {
        enum bpf_prog_type ptype;
-       struct bpf_prog *prog;
-       struct cgroup *cgrp;
-       int ret;
 
        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

@@ -1667,19 +1592,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
                return -EINVAL;
        }
 
-       cgrp = cgroup_get_from_fd(attr->target_fd);
-       if (IS_ERR(cgrp))
-               return PTR_ERR(cgrp);
-
-       prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
-       if (IS_ERR(prog))
-               prog = NULL;
-
-       ret = cgroup_bpf_detach(cgrp, prog, attr->attach_type, 0);
-       if (prog)
-               bpf_prog_put(prog);
-       cgroup_put(cgrp);
-       return ret;
+       return cgroup_bpf_prog_detach(attr, ptype);
 }
 
 #define BPF_PROG_QUERY_LAST_FIELD query.prog_cnt

@@ -1687,9 +1600,6 @@ static int bpf_prog_detach(const union bpf_attr *attr)
 static int bpf_prog_query(const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
 {
-       struct cgroup *cgrp;
-       int ret;
-
        if (!capable(CAP_NET_ADMIN))
                return -EPERM;
        if (CHECK_ATTR(BPF_PROG_QUERY))

@@ -1717,14 +1627,9 @@ static int bpf_prog_query(const union bpf_attr *attr,
        default:
                return -EINVAL;
        }
-       cgrp = cgroup_get_from_fd(attr->query.target_fd);
-       if (IS_ERR(cgrp))
-               return PTR_ERR(cgrp);
-       ret = cgroup_bpf_query(cgrp, attr, uattr);
-       cgroup_put(cgrp);
-       return ret;
+
+       return cgroup_bpf_prog_query(attr, uattr);
 }
-#endif /* CONFIG_CGROUP_BPF */
 
 #define BPF_PROG_TEST_RUN_LAST_FIELD test.duration
 

@@ -2371,7 +2276,6 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
        case BPF_OBJ_GET:
                err = bpf_obj_get(&attr);
                break;
-#ifdef CONFIG_CGROUP_BPF
        case BPF_PROG_ATTACH:
                err = bpf_prog_attach(&attr);
                break;

@@ -2381,7 +2285,6 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
        case BPF_PROG_QUERY:
                err = bpf_prog_query(&attr, uattr);
                break;
-#endif
        case BPF_PROG_TEST_RUN:
                err = bpf_prog_test_run(&attr, uattr);
                break;
--

2.17.1

Quoted 2 lines · Sean Young

Compile bpf_prog_{attach,detach,query} even if CONFIG_BPF_CGROUP is not set.

It should be CONFIG_CGROUP_BPF here. The same for subject line. Today, if CONFIG_CGROUP_BPF is not defined. Users will get an -EINVAL if they try to attach/detach/query.

I am not sure what is the motivation behind this change. Could you explain more?

Quoted 7 lines

Signed-off-by Sean Young <[email protected]>

---
 include/linux/bpf-cgroup.h |  31 +++++++++++
 kernel/bpf/cgroup.c        | 110 +++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c       | 105 ++---------------------------------
 3 files changed, 145 insertions(+), 101 deletions(-)

[...]

If the kernel is compiled with CONFIG_CGROUP_BPF not enabled, it is not possible to attach, detach or query IR BPF programs to /dev/lircN devices, making them impossible to use. For embedded devices, it should be possible to use IR decoding without cgroups or CONFIG_CGROUP_BPF enabled.

This change requires some refactoring, since bpf_prog_{attach,detach,query} functions are now always compiled, but their code paths for cgroups need moving out. Rather than a #ifdef CONFIG_CGROUP_BPF in kernel/bpf/syscall.c, moving them to kernel/bpf/cgroup.c does not require #ifdefs since that file is already conditionally compiled.

Signed-off-by Sean Young <[email protected]>

 include/linux/bpf-cgroup.h |  31 +++++++++++
 kernel/bpf/cgroup.c        | 110 +++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c       | 105 ++---------------------------------
 3 files changed, 145 insertions(+), 101 deletions(-)

include/linux/bpf-cgroup.h +31 -0

index 975fb4cf1bb7..ee67cd35f426 100644
@@ -188,12 +188,43 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor,
 									      \
 	__ret;								      \
 })
+int sockmap_get_from_fd(const union bpf_attr *attr, int type, bool attach);
+int cgroup_bpf_prog_attach(const union bpf_attr *attr,
+			   enum bpf_prog_type ptype);
+int cgroup_bpf_prog_detach(const union bpf_attr *attr,
+			   enum bpf_prog_type ptype);
+int cgroup_bpf_prog_query(const union bpf_attr *attr,
+			  union bpf_attr __user *uattr);
 #else
 
 struct cgroup_bpf {};
 static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
 static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
 
+static inline int sockmap_get_from_fd(const union bpf_attr *attr,
+				      int type, bool attach)
+{
+	return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_attach(const union bpf_attr *attr,
+					 enum bpf_prog_type ptype)
+{
+	return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_detach(const union bpf_attr *attr,
+					 enum bpf_prog_type ptype)
+{
+	return -EINVAL;
+}
+
+static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
+					union bpf_attr __user *uattr)
+{
+	return -EINVAL;
+}
+
 #define cgroup_bpf_enabled (0)
 #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (0)
 #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })

kernel/bpf/cgroup.c +1 -0

index f7c00bd6f8e4..d6e18f9dc0c4 100644
@@ -428,6 +428,116 @@ int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
 	return ret;
 }
 
+int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,

kernel/bpf/cgroup.c +22 -0

+int sockmap_get_from_fd(const union bpf_attr *attr, int type, bool attach)
+{
+	struct bpf_prog *prog = NULL;
+	int ufd = attr->target_fd;
+	struct bpf_map *map;
+	struct fd f;
+	int err;
+
+	f = fdget(ufd);
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	if (attach) {
+		prog = bpf_prog_get_type(attr->attach_bpf_fd, type);
+		if (IS_ERR(prog)) {
+			fdput(f);
+			return PTR_ERR(prog);
+		}
+	}
+
+	err = sock_map_prog(map, prog, attr->attach_type);

Hi Sean,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.18-rc1 next-20180618]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Sean-Young/bpf-attach-type-BPF_LIRC_MODE2-should-not-depend-on-CONFIG_CGROUP_BPF/20180619-023056
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0 reproduce:

        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

In file included from kernel///events/core.c:45:0:

Quoted 1 line

Quoted 1 line

include/linux/bpf.h:710:1: error: expected identifier or '(' before '{' token

    {
    ^

If the kernel is compiled with CONFIG_CGROUP_BPF not enabled, it is not possible to attach, detach or query IR BPF programs to /dev/lircN devices, making them impossible to use. For embedded devices, it should be possible to use IR decoding without cgroups or CONFIG_CGROUP_BPF enabled.

This change requires some refactoring, since bpf_prog_{attach,detach,query} functions are now always compiled, but their code paths for cgroups need moving out. Rather than a #ifdef CONFIG_CGROUP_BPF in kernel/bpf/syscall.c, moving them to kernel/bpf/cgroup.c and kernel/bpf/sockmap.c does not require #ifdefs since that is already conditionally compiled.

Signed-off-by Sean Young <[email protected]>

The kernel IR decoders (drivers/media/rc/ir-*-decoder.c) support the most widely used IR protocols, but there are many protocols which are not supported[1]. For example, the lirc-remotes[2] repo has over 2700 remotes, many of which are not supported by rc-core. There is a "long tail" of unsupported IR protocols, for which lircd is need to decode the IR .

IR encoding is done in such a way that some simple circuit can decode it; therefore, bpf is ideal.

In order to support all these protocols, here we have bpf based IR decoding. The idea is that user-space can define a decoder in bpf, attach it to the rc device through the lirc chardev.

Separate work is underway to extend ir-keytable to have an extensive library of bpf-based decoders, and a much expanded library of rc keymaps.

Another future application would be to compile IRP[3] to a IR BPF program, and so support virtually every remote without having to write a decoder for each. It might also be possible to support non-button devices such as analog directional pads or air conditioning remote controls and decode the target temperature in bpf, and pass that to an input device.

Thanks,

Sean Young

[1] http://www.hifi-remote.com/wiki/index.php?title=DecodeIR
[2] https://sourceforge.net/p/lirc-remotes/code/ci/master/tree/remotes/
[3] http://www.hifi-remote.com/wiki/index.php?title=IRP_Notation

Changes since v4:
- Renamed rc_dev_bpf_{attach,detach,query} to lirc_bpf_{attach,detach,query}
- Fixed error path in lirc_bpf_query
- Rebased on bpf-next

Changes since v3:
- Implemented review comments from Quentin Monnet and Y Song (thanks!)
- More helpful and better formatted bpf helper documentation
- Changed back to bpf_prog_array rather than open-coded implementation
- scancodes can be 64 bit
- bpf gets passed values in microseconds, not nanoseconds. microseconds is more than than enough (IR receivers support carriers upto 70kHz, at which point a single period is already 14 microseconds). Also, this makes it much more consistent with lirc mode2.
- Since it looks much more like lirc mode2, rename the program type to BPF_PROG_TYPE_LIRC_MODE2.
- Rebased on bpf-next

Changes since v2:
- Fixed locking issues
- Improved self-test to cover more cases
- Rebased on bpf-next again

Changes since v1:
- Code review comments from Y Song <[email protected]> and Randy Dunlap <[email protected]>
- Re-wrote sample bpf to be selftest
- Renamed RAWIR_DECODER -> RAWIR_EVENT (Kconfig, context, bpf prog type)
- Rebase on bpf-next
- Introduced bpf_rawir_event context structure with simpler access checking