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modified post f76c47 by Anonymous on Wed 6th Jul 2022 18:29
original post ce2 by Anonymous on Wed 6th Jul 2022 12:53
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--- /dev/null	2022-04-19 22:28:32.062891741 +0200

1	1		--- /dev/null 2022-04-19 22:28:32.062891741 +0200
2		-	+++ pthread_interceptor.c 2022-07-06 13:47:43.337141261 +0200
	2	+	+++ pthread_interceptor.c 2022-07-06 19:28:52.893103035 +0200
3		-	@@ -0,0 +1,86 @@
	3	+	@@ -0,0 +1,90 @@
4	4		+/*
5	5		+ * pthread_interceptor.c
6	6		+ *
7		-	+ * intercept pthread calls liek \|pthread_mutex_init()\| via LD_PRELOAD
	7	+	+ * intercept pthread calls
	8	+	+ * (like \|pthread_mutex_init()\|) via LD_PRELOAD
8	9		+ *
	10	+	+ * Example usage:
9	13		+ * Written by Roland Mainz <roland.mainz@nrubsig.org>
10	14		+ */
11	15		+
12	16		+#define _GNU_SOURCE 1 /* needed for \|RTLD_NEXT\| */
13	17		+
14	18		+#include <pthread.h>
15	19		+#include <unistd.h>
16	20		+#include <errno.h>
17	21		+#include <stdio.h>
18	22		+#include <string.h>
19	23		+#include <stdbool.h>
20	24		+#include <dlfcn.h>
21	25		+
22	26		+/* config */
23	27		+#define PICFG_PRINT_ONCE_MSG 1
24	28		+#define PICFG_ENFORCE_PRIO_INHERIT 1
25	29		+
26	30		+/* misc */
27	31		+#define STDERR_MSG(msg) \
28	32		+ (void)write(STDERR_FILENO, (msg), strlen(msg))
29	33		+
30	34		+
31	35		+/*
32	36		+ * interceptor for \|pthread_mutex_init()\|
33	37		+ */
34	38		+int pthread_mutex_init(pthread_mutex_t *restrict mutex,
35	39		+ const pthread_mutexattr_t *restrict attr) {
36	40		+ pthread_mutexattr_t xattr = (pthread_mutexattr_t )attr;
37	41		+ int pmi_res;
38	42		+ int pmi_errno;
39	43		+
40	44		+#if PICFG_PRINT_ONCE_MSG
41	45		+ static int once = 0;
42	46		+ const char *mymessage = "pthread_interceptor.so: "
43	47		+ "Once: In our own pthread_mutex_init()\n";
44		-	+ /* just print message ONCE */
	48	+	+ /* just print message ONCE (BUG: every INT_MAX times) */
45	49		+ if (once++ == 0)
46	50		+ STDERR_MSG(mymessage);
47	51		+#endif /* PICFG_PRINT_ONCE_MSG */
48	52		+
49	53		+ int (original_pthread_mutex_init)(pthread_mutex_t restrict mutex,
50	54		+ const pthread_mutexattr_t *restrict attr);
51	55		+ original_pthread_mutex_init = dlsym(RTLD_NEXT, "pthread_mutex_init");
52	56		+
53	57		+ pthread_mutexattr_t myattr;
54	58		+ bool myattr_used = false;
55	59		+
56	60		+ if (!xattr) {
57	61		+ (void)pthread_mutexattr_init(&myattr);
58	62		+ myattr_used = true;
59	63		+ xattr = &myattr;
60	64		+ }
61	65		+
62	66		+#if PICFG_ENFORCE_PRIO_INHERIT
63	67		+ int mutex_protocol = -666;
64	68		+ (void)pthread_mutexattr_getprotocol(xattr, &mutex_protocol);
65	69		+ if (mutex_protocol != PTHREAD_PRIO_INHERIT) {
66	70		+ char msgbuff[256]; /* fixed size, but no \|malloc()\| allowed here */
67	71		+
68	72		+ (void)pthread_mutexattr_setprotocol(xattr, PTHREAD_PRIO_INHERIT);
69	73		+ (void)snprintf(msgbuff,
70	74		+ sizeof(msgbuff),
71	75		+ "pthread_interceptor.so: "
72	76		+ "PTHREAD_PRIO_INHERIT enforced "
73	77		+ "for mutex=0x%lx, was protocol=%d\n",
74	78		+ (unsigned long)(void *)mutex,
75	79		+ mutex_protocol);
76	80		+ STDERR_MSG(msgbuff);
77	81		+ }
78	82		+#endif /* PICFG_ENFORCE_PRIO_INHERIT */
79	83		+
80	84		+ pmi_res = (*original_pthread_mutex_init)(mutex, xattr);
81	85		+ pmi_errno = errno;
82	86		+
83	87		+ if (myattr_used) {
84	88		+ (void)pthread_mutexattr_destroy(&myattr);
85	89		+ }
86	90		+
87	91		+ errno = pmi_errno;
88	92		+ return pmi_res;
89	93		+}
90	94		--- /dev/null 2022-04-19 22:28:32.062891741 +0200
91	95		+++ test1.c 2022-07-06 13:52:16.151772792 +0200
92	96		@@ -0,0 +1,27 @@
93	97		+/*
94	98		+ * test1 for pthread_interceptor.c
95	99		+ *
96	100		+ */
97	101		+
98	102		+#include <stdlib.h>
99	103		+#include <stdio.h>
100	104		+#include <pthread.h>
101	105		+#include <errno.h>
102	106		+
103	107		+int main(int ac, char *av[])
104	108		+{
105	109		+ (void)puts("# start.");
106	110		+
107	111		+ pthread_mutex_t mutex1;
108	112		+ pthread_mutex_t mutex2;
109	113		+
110	114		+ (void)pthread_mutex_init(&mutex1, NULL);
111	115		+ perror("pthread_mutex_init(1) result");
112	116		+
113	117		+ (void)pthread_mutex_init(&mutex2, NULL);
114	118		+ perror("pthread_mutex_init(2) result");
115	119		+
116	120		+ (void)puts("# end.");
117	121		+
118	122		+ return EXIT_SUCCESS;
119	123		+}
120	124		--- /dev/null 2022-04-19 22:28:32.062891741 +0200
121		-	+++ Makefile 2022-07-06 13:50:52.426969179 +0200
	125	+	+++ Makefile 2022-07-06 19:26:43.063939487 +0200
122		-	@@ -0,0 +1,24 @@
	126	+	@@ -0,0 +1,34 @@
123	127		+#
124	128		+# Makefile for LD_PRELOAD pthreadinterceptor
125	129		+#
126	130		+
127	131		+CSTDFLAGS=-std=c11
	132	+	+CARCHFLAGS=-m64 # -m32 or -m64
128	133		+CC=gcc # gcc or clang
129	134		+
	135	+	+#
130	138		+pthread_interceptor.o: pthread_interceptor.c
131		-	+ $(CC) $(CSTDFLAGS) -Wall -g pthread_interceptor.c -fPIC -c -o pthread_interceptor.o
	139	+	+ $(CC) $(CSTDFLAGS) $(CARCHFLAGS) -Wall -g pthread_interceptor.c -fPIC -c -o pthread_interceptor.o
132	140		+pthread_interceptor.so: pthread_interceptor.o
133		-	+ $(CC) $(CSTDFLAGS) -Wall -g pthread_interceptor.o -fPIC -shared -ldl -lpthread -o pthread_interceptor.so
	141	+	+ $(CC) $(CSTDFLAGS) $(CARCHFLAGS) -Wall -g pthread_interceptor.o -fPIC -shared -ldl -lpthread -o pthread_interceptor.so
134	142		+
	143	+	+#
135	146		+test1: test1.c
136		-	+ $(CC) $(CSTDFLAGS) -Wall -g test1.c -o test1
	147	+	+ $(CC) $(CSTDFLAGS) $(CARCHFLAGS) -Wall -g test1.c -o test1
137	148		+
138	149		+run_test: test1 pthread_interceptor.so
139		-	+ ksh93 -c 'LD_PRELOAD=$$PWD/pthread_interceptor.so ./test1'
	150	+	+ ksh93 -c 'LD_PRELOAD="$$PWD/pthread_interceptor.so" ./test1'
140	151		+
	152	+	+#
141	155		+all: run_test
142	156		+
143	157		+clean:
144	158		+ rm -f .o .so test1
145	159		+
146	160		+# EOF.
147	161