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Subject: keytable: ensure we have enough memlock pages
Author:  Sean Young <s...@mess.org>
Date:    Wed Sep 4 11:03:24 2019 +0100

Since kernel v5.2, BPF maps and programs are charged against
RLIMT_MEMLOCK. By default this limit is 64KB however all of these are
already taken (16 pages on x86) by the time we've booted on Fedora. This
results in a permission denied error.

The error message is confusing since it happens when running as root.
systemd works around this problem by setting setrlimit(RLIMIT_MEMLOCK)
to 64MB. Do the the same.

Signed-off-by: Sean Young <s...@mess.org>
(cherry picked from commit 7530ca0b53c921f681af9d02a1f1958185dce2d2)

 utils/keytable/keytable.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

---

http://git.linuxtv.org/cgit.cgi/v4l-utils.git/commit/?id=21bbb1a5723f0f60e800408175f0a62e82946971
diff --git a/utils/keytable/keytable.c b/utils/keytable/keytable.c
index 46074ee9ef41..b0727e5a326d 100644
--- a/utils/keytable/keytable.c
+++ b/utils/keytable/keytable.c
@@ -25,6 +25,7 @@
 #include <linux/lirc.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <dirent.h>
 #include <argp.h>
@@ -1852,9 +1853,14 @@ static void device_info(int fd, char *prepend)
 
 #ifdef HAVE_BPF
 #define MAX_PROGS 64
+// This value is what systemd sets PID 1 to, see:
+// https://github.com/systemd/systemd/blob/master/src/basic/def.h#L60
+#define HIGH_RLIMIT_MEMLOCK (1024ULL*1024ULL*64ULL)
+
 static void attach_bpf(const char *lirc_name, const char *bpf_prog, struct 
toml_table_t *toml)
 {
        unsigned int features;
+       struct rlimit rl;
        int fd;
 
        fd = open(lirc_name, O_RDONLY);
@@ -1875,6 +1881,14 @@ static void attach_bpf(const char *lirc_name, const char 
*bpf_prog, struct toml_
                return;
        }
 
+       // BPF programs are charged against RLIMIT_MEMLOCK. We'll need pages
+       // for the state, program text, and any raw IR. None of these are
+       // particularly large. However, the kernel defaults to 64KB
+       // memlock, which is only 16 pages which are mostly used by the
+       // time we are trying to load our BPF program.
+       rl.rlim_cur = rl.rlim_max = HIGH_RLIMIT_MEMLOCK;
+       (void) setrlimit(RLIMIT_MEMLOCK, &rl);
+
        load_bpf_file(bpf_prog, fd, toml);
        close(fd);
 }

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