6 files changed, 235 insertions, 0 deletions
diff --git a/schulung_tools/ipc_shm/Makefile b/schulung_tools/ipc_shm/Makefile
new file mode 100644
index 0000000..0c6ca9e
--- /dev/null
+++ b/schulung_tools/ipc_shm/Makefile
@@ -0,0 +1,25 @@
+CC = $(CROSS_COMPILE)gcc
+CFLAGS = -Wall -Werror -g -O0 -std=c99 -D_GNU_SOURCE
+LDFLAGS = -lpthread -lrt shm.c
+CFLAGS += \
+	-Wchar-subscripts \
+	-Wmissing-declarations \
+	-Wmissing-prototypes \
+	-Wnested-externs \
+	-Wpointer-arith \
+	-Wcast-align \
+	-Wfloat-equal \
+	-Wsign-compare
+
+all: recv send
+
+recv: recv.c shm.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -o$@ $<
+
+send: send.c shm.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -o$@ $<
+
+clean:
+	rm -f send recv
+
+.PHONY: clean all
diff --git a/schulung_tools/ipc_shm/README b/schulung_tools/ipc_shm/README
new file mode 100644
index 0000000..bea6c98
--- /dev/null
+++ b/schulung_tools/ipc_shm/README
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+# build programs send/recv
+make
+
+# find uprobe offsets (search for "uprobe")
+objdump -D -F -S send | less
+objdump -D -F -S recv | less
+
+# create uprobe events (as root)
+echo "p:sending `pwd`/send:0x1055" > /sys/kernel/debug/tracing/uprobe_events
+echo "p:received `pwd`/recv:0xff1" >> /sys/kernel/debug/tracing/uprobe_events
+
+# run receiver
+sudo taskset 1 chrt -f 80 ./recv &
+
+# run sender (wrapping with trace-cmd)
+sudo trace-cmd record \
+	-e sched:sched_switch \
+	-e sched:sched_wakeup \
+	-e sched:sched_pi_setprio \
+	-e uprobes:sending \
+	-e uprobes:received \
+	-e raw_syscalls:sys_enter \
+	-e raw_syscalls:sys_exit \
+	taskset 1 chrt -f 70 ./send
+(type message and hit return)
+
+# view results
+kernelshark
diff --git a/schulung_tools/ipc_shm/recv.c b/schulung_tools/ipc_shm/recv.c
new file mode 100644
index 0000000..8a08338
--- /dev/null
+++ b/schulung_tools/ipc_shm/recv.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include "shm.h"
+
+int main(void)
+{
+	struct share_data *data;
+	int rv;
+
+	if (create_share() != 0)
+		return 1;
+
+	data = get_share();
+	if (!data)
+		return 1;
+
+	init_share(data);
+
+	if (pthread_mutex_lock(&data->m) != 0)
+		return 1;
+
+	printf("recv (%d): waiting for signal\n", getpid());
+
+	do {
+		rv = pthread_cond_wait(&data->c, &data->m);
+		if (rv != 0) {
+			if (rv == EOWNERDEAD) {
+				printf("recv(%d): recover mutex\n", getpid());
+				data->msg[0] = 0;
+				pthread_mutex_consistent(&data->m);
+			} else {
+				/* maybe rv == ENOTRECOVERABLE */
+				return 1;
+			}
+		}
+	} while (rv != 0);
+
+	/* set "received" uprobe here */
+
+	printf("recv (%d): received signal: %s\n", getpid(), data->msg);
+	pthread_mutex_unlock(&data->m);
+
+	remove_share();
+
+	return 0;
+}
diff --git a/schulung_tools/ipc_shm/send.c b/schulung_tools/ipc_shm/send.c
new file mode 100644
index 0000000..028610f
--- /dev/null
+++ b/schulung_tools/ipc_shm/send.c
@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include "shm.h"
+
+int main(void)
+{
+	struct share_data *data;
+	int rv;
+
+	data = get_share();
+	if (!data)
+		return 1;
+
+	rv = pthread_mutex_lock(&data->m);
+	if (rv != 0) {
+		if (rv == EOWNERDEAD) {
+			printf("send (%d): recover mutex\n", getpid());
+			data->msg[0] = 0;
+			pthread_mutex_consistent(&data->m);
+		} else {
+			/* maybe rv == ENOTRECOVERABLE */
+			return 1;
+		}
+	}
+
+	printf("send (%d): type message and hit RETURN to send signal\n",
+	       getpid());
+	fgets(data->msg, sizeof(data->msg), stdin);
+
+	/* set "sending" uprobe here */
+
+	pthread_cond_signal(&data->c);
+	pthread_mutex_unlock(&data->m);
+
+	sleep(1);
+
+	return 0;
+}
diff --git a/schulung_tools/ipc_shm/shm.c b/schulung_tools/ipc_shm/shm.c
new file mode 100644
index 0000000..777fe79
--- /dev/null
+++ b/schulung_tools/ipc_shm/shm.c
@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include "shm.h"
+
+#define SHARE_NAME "/ipc.shm"
+
+/* open and return a pointer to shared data */
+struct share_data *get_share(void)
+{
+	struct share_data *data;
+	int fd;
+
+	fd = shm_open(SHARE_NAME, O_RDWR, 0);
+	if (fd == -1)
+		return NULL;
+
+	data = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ | PROT_WRITE,
+		    MAP_SHARED, fd, 0);
+	if (data == MAP_FAILED) {
+		close(fd);
+		return NULL;
+	}
+
+	close(fd);
+
+	return data;
+}
+
+/* initialize shared data */
+void init_share(struct share_data *data)
+{
+	pthread_mutexattr_t mattr;
+	pthread_condattr_t cattr;
+
+	pthread_mutexattr_init(&mattr);
+	pthread_mutexattr_setprotocol(&mattr, PTHREAD_PRIO_INHERIT);
+	pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
+	pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
+	pthread_mutex_init(&data->m, &mattr);
+
+	pthread_condattr_init(&cattr);
+	pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
+	pthread_cond_init(&data->c, &cattr);
+}
+
+/* create a zero'd out file of size 1 page */
+int create_share(void)
+{
+	int ret;
+	int fd;
+
+	fd = shm_open(SHARE_NAME, O_CREAT|O_RDWR, S_IRUSR|S_IWUSR);
+	if (fd == -1)
+		return -1;
+
+	ret = ftruncate(fd, sysconf(_SC_PAGESIZE));
+
+	close(fd);
+
+	return ret;
+}
+
+/* remove the share */
+void remove_share(void)
+{
+	shm_unlink(SHARE_NAME);
+}
diff --git a/schulung_tools/ipc_shm/shm.h b/schulung_tools/ipc_shm/shm.h
new file mode 100644
index 0000000..35acd0a
--- /dev/null
+++ b/schulung_tools/ipc_shm/shm.h
@@ -0,0 +1,17 @@
+#ifndef _SHM_H
+#define _SHM_H
+
+#include <pthread.h>
+
+struct share_data {
+	pthread_mutex_t m;
+	pthread_cond_t c;
+	char msg[2048];
+};
+
+extern int create_share(void);
+extern void init_share(struct share_data *data);
+extern struct share_data *get_share(void);
+extern void remove_share(void);
+
+#endif /* _SHM_H */