uml: replace clone with fork

Convert the boot-time host ptrace testing from clone to fork. They were essentially doing fork anyway. This cleans up the code a bit, and makes valgrind a bit happier about grinding it. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

uml: replace clone with fork
Convert the boot-time host ptrace testing from clone to fork. They were essentially doing fork anyway. This cleans up the code a bit, and makes valgrind a bit happier about grinding it. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jeff Dike · Linus Torvalds
1 parent 8ca842c4b5
Showing 1 changed file with 20 additions and 35 deletions Side-by-side Diff
arch/um/os-Linux/start_up.c
@@ -25,7 +25,7 @@
 #include "registers.h"
 #include "skas_ptrace.h"
  
-static int ptrace_child(void *arg)
+static int ptrace_child(void)
 {
 	int ret;
 	int pid = os_getpid(), ppid = getppid();
  
  
  
  
  
@@ -90,31 +90,23 @@
 	fflush(stdout);
 }
  
-static int start_ptraced_child(void **stack_out)
+static int start_ptraced_child(void)
 {
-	void *stack;
-	unsigned long sp;
 	int pid, n, status;
  
-	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
-		     PROT_READ | PROT_WRITE | PROT_EXEC,
-		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-	if (stack == MAP_FAILED)
-		fatal_perror("check_ptrace : mmap failed");
+	pid = fork();
+	if (pid == 0)
+		ptrace_child();
+	else if (pid < 0)
+		fatal_perror("start_ptraced_child : fork failed");
  
-	sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
-	pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
-	if (pid < 0)
-		fatal_perror("start_ptraced_child : clone failed");
-
 	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
 	if (n < 0)
-		fatal_perror("check_ptrace : clone failed");
+		fatal_perror("check_ptrace : waitpid failed");
 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
 		fatal("check_ptrace : expected SIGSTOP, got status = %d",
 		      status);
  
-	*stack_out = stack;
 	return pid;
 }
  
@@ -124,8 +116,7 @@
  * So only for SYSEMU features we test mustpanic, while normal host features
  * must work anyway!
  */
-static int stop_ptraced_child(int pid, void *stack, int exitcode,
-			      int mustexit)
+static int stop_ptraced_child(int pid, int exitcode, int mustexit)
 {
 	int status, n, ret = 0;
  
@@ -145,8 +136,6 @@
 		ret = -1;
 	}
  
-	if (munmap(stack, UM_KERN_PAGE_SIZE) < 0)
-		fatal_perror("check_ptrace : munmap failed");
 	return ret;
 }
  
  
@@ -198,13 +187,12 @@
  
 static void __init check_sysemu(void)
 {
-	void *stack;
 	unsigned long regs[MAX_REG_NR];
 	int pid, n, status, count=0;
  
 	non_fatal("Checking syscall emulation patch for ptrace...");
 	sysemu_supported = 0;
-	pid = start_ptraced_child(&stack);
+	pid = start_ptraced_child();
  
 	if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
 		goto fail;
@@ -231,7 +219,7 @@
 		goto fail;
 	}
  
-	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+	if (stop_ptraced_child(pid, 0, 0) < 0)
 		goto fail_stopped;
  
 	sysemu_supported = 1;
@@ -239,7 +227,7 @@
 	set_using_sysemu(!force_sysemu_disabled);
  
 	non_fatal("Checking advanced syscall emulation patch for ptrace...");
-	pid = start_ptraced_child(&stack);
+	pid = start_ptraced_child();
  
 	if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 		   (void *) PTRACE_O_TRACESYSGOOD) < 0))
@@ -271,7 +259,7 @@
 			fatal("check_ptrace : expected SIGTRAP or "
 			      "(SIGTRAP | 0x80), got status = %d", status);
 	}
-	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+	if (stop_ptraced_child(pid, 0, 0) < 0)
 		goto fail_stopped;
  
 	sysemu_supported = 2;
  
  
@@ -282,18 +270,17 @@
 	return;
  
 fail:
-	stop_ptraced_child(pid, stack, 1, 0);
+	stop_ptraced_child(pid, 1, 0);
 fail_stopped:
 	non_fatal("missing\n");
 }
  
 static void __init check_ptrace(void)
 {
-	void *stack;
 	int pid, syscall, n, status;
  
 	non_fatal("Checking that ptrace can change system call numbers...");
-	pid = start_ptraced_child(&stack);
+	pid = start_ptraced_child();
  
 	if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
 		   (void *) PTRACE_O_TRACESYSGOOD) < 0))
@@ -323,7 +310,7 @@
 			break;
 		}
 	}
-	stop_ptraced_child(pid, stack, 0, 1);
+	stop_ptraced_child(pid, 0, 1);
 	non_fatal("OK\n");
 	check_sysemu();
 }
  
@@ -403,11 +390,10 @@
 static inline void check_skas3_ptrace_faultinfo(void)
 {
 	struct ptrace_faultinfo fi;
-	void *stack;
 	int pid, n;
  
 	non_fatal("  - PTRACE_FAULTINFO...");
-	pid = start_ptraced_child(&stack);
+	pid = start_ptraced_child();
  
 	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 	if (n < 0) {
  
@@ -425,13 +411,12 @@
 	}
  
 	init_registers(pid);
-	stop_ptraced_child(pid, stack, 1, 1);
+	stop_ptraced_child(pid, 1, 1);
 }
  
 static inline void check_skas3_ptrace_ldt(void)
 {
 #ifdef PTRACE_LDT
-	void *stack;
 	int pid, n;
 	unsigned char ldtbuf[40];
 	struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
@@ -440,7 +425,7 @@
 		.bytecount = sizeof(ldtbuf)};
  
 	non_fatal("  - PTRACE_LDT...");
-	pid = start_ptraced_child(&stack);
+	pid = start_ptraced_child();
  
 	n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
 	if (n < 0) {
@@ -458,7 +443,7 @@
 			non_fatal("found, but use is disabled\n");
 	}
  
-	stop_ptraced_child(pid, stack, 1, 1);
+	stop_ptraced_child(pid, 1, 1);
 #else
 	/* PTRACE_LDT might be disabled via cmdline option.
 	 * We want to override this, else we might use the stub
...	...	@@ -25,7 +25,7 @@
25	25	#include "registers.h"
26	26	#include "skas_ptrace.h"
27	27
28		-static int ptrace_child(void *arg)
	28	+static int ptrace_child(void)
29	29	{
30	30	int ret;
31	31	int pid = os_getpid(), ppid = getppid();
32	32
33	33
34	34
35	35
36	36
...	...	@@ -90,31 +90,23 @@
90	90	fflush(stdout);
91	91	}
92	92
93		-static int start_ptraced_child(void **stack_out)
	93	+static int start_ptraced_child(void)
94	94	{
95		- void *stack;
96		- unsigned long sp;
97	95	int pid, n, status;
98	96
99		- stack = mmap(NULL, UM_KERN_PAGE_SIZE,
100		- PROT_READ \| PROT_WRITE \| PROT_EXEC,
101		- MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
102		- if (stack == MAP_FAILED)
103		- fatal_perror("check_ptrace : mmap failed");
	97	+ pid = fork();
	98	+ if (pid == 0)
	99	+ ptrace_child();
	100	+ else if (pid < 0)
	101	+ fatal_perror("start_ptraced_child : fork failed");
104	102
105		- sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
106		- pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
107		- if (pid < 0)
108		- fatal_perror("start_ptraced_child : clone failed");
109		-
110	103	CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
111	104	if (n < 0)
112		- fatal_perror("check_ptrace : clone failed");
	105	+ fatal_perror("check_ptrace : waitpid failed");
113	106	if (!WIFSTOPPED(status) \|\| (WSTOPSIG(status) != SIGSTOP))
114	107	fatal("check_ptrace : expected SIGSTOP, got status = %d",
115	108	status);
116	109
117		- *stack_out = stack;
118	110	return pid;
119	111	}
120	112
...	...	@@ -124,8 +116,7 @@
124	116	* So only for SYSEMU features we test mustpanic, while normal host features
125	117	* must work anyway!
126	118	*/
127		-static int stop_ptraced_child(int pid, void *stack, int exitcode,
128		- int mustexit)
	119	+static int stop_ptraced_child(int pid, int exitcode, int mustexit)
129	120	{
130	121	int status, n, ret = 0;
131	122
...	...	@@ -145,8 +136,6 @@
145	136	ret = -1;
146	137	}
147	138
148		- if (munmap(stack, UM_KERN_PAGE_SIZE) < 0)
149		- fatal_perror("check_ptrace : munmap failed");
150	139	return ret;
151	140	}
152	141
153	142
...	...	@@ -198,13 +187,12 @@
198	187
199	188	static void __init check_sysemu(void)
200	189	{
201		- void *stack;
202	190	unsigned long regs[MAX_REG_NR];
203	191	int pid, n, status, count=0;
204	192
205	193	non_fatal("Checking syscall emulation patch for ptrace...");
206	194	sysemu_supported = 0;
207		- pid = start_ptraced_child(&stack);
	195	+ pid = start_ptraced_child();
208	196
209	197	if (ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
210	198	goto fail;
...	...	@@ -231,7 +219,7 @@
231	219	goto fail;
232	220	}
233	221
234		- if (stop_ptraced_child(pid, stack, 0, 0) < 0)
	222	+ if (stop_ptraced_child(pid, 0, 0) < 0)
235	223	goto fail_stopped;
236	224
237	225	sysemu_supported = 1;
...	...	@@ -239,7 +227,7 @@
239	227	set_using_sysemu(!force_sysemu_disabled);
240	228
241	229	non_fatal("Checking advanced syscall emulation patch for ptrace...");
242		- pid = start_ptraced_child(&stack);
	230	+ pid = start_ptraced_child();
243	231
244	232	if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
245	233	(void *) PTRACE_O_TRACESYSGOOD) < 0))
...	...	@@ -271,7 +259,7 @@
271	259	fatal("check_ptrace : expected SIGTRAP or "
272	260	"(SIGTRAP \| 0x80), got status = %d", status);
273	261	}
274		- if (stop_ptraced_child(pid, stack, 0, 0) < 0)
	262	+ if (stop_ptraced_child(pid, 0, 0) < 0)
275	263	goto fail_stopped;
276	264
277	265	sysemu_supported = 2;
278	266
279	267
...	...	@@ -282,18 +270,17 @@
282	270	return;
283	271
284	272	fail:
285		- stop_ptraced_child(pid, stack, 1, 0);
	273	+ stop_ptraced_child(pid, 1, 0);
286	274	fail_stopped:
287	275	non_fatal("missing\n");
288	276	}
289	277
290	278	static void __init check_ptrace(void)
291	279	{
292		- void *stack;
293	280	int pid, syscall, n, status;
294	281
295	282	non_fatal("Checking that ptrace can change system call numbers...");
296		- pid = start_ptraced_child(&stack);
	283	+ pid = start_ptraced_child();
297	284
298	285	if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
299	286	(void *) PTRACE_O_TRACESYSGOOD) < 0))
...	...	@@ -323,7 +310,7 @@
323	310	break;
324	311	}
325	312	}
326		- stop_ptraced_child(pid, stack, 0, 1);
	313	+ stop_ptraced_child(pid, 0, 1);
327	314	non_fatal("OK\n");
328	315	check_sysemu();
329	316	}
330	317
...	...	@@ -403,11 +390,10 @@
403	390	static inline void check_skas3_ptrace_faultinfo(void)
404	391	{
405	392	struct ptrace_faultinfo fi;
406		- void *stack;
407	393	int pid, n;
408	394
409	395	non_fatal(" - PTRACE_FAULTINFO...");
410		- pid = start_ptraced_child(&stack);
	396	+ pid = start_ptraced_child();
411	397
412	398	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
413	399	if (n < 0) {
414	400
...	...	@@ -425,13 +411,12 @@
425	411	}
426	412
427	413	init_registers(pid);
428		- stop_ptraced_child(pid, stack, 1, 1);
	414	+ stop_ptraced_child(pid, 1, 1);
429	415	}
430	416
431	417	static inline void check_skas3_ptrace_ldt(void)
432	418	{
433	419	#ifdef PTRACE_LDT
434		- void *stack;
435	420	int pid, n;
436	421	unsigned char ldtbuf[40];
437	422	struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
...	...	@@ -440,7 +425,7 @@
440	425	.bytecount = sizeof(ldtbuf)};
441	426
442	427	non_fatal(" - PTRACE_LDT...");
443		- pid = start_ptraced_child(&stack);
	428	+ pid = start_ptraced_child();
444	429
445	430	n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
446	431	if (n < 0) {
...	...	@@ -458,7 +443,7 @@
458	443	non_fatal("found, but use is disabled\n");
459	444	}
460	445
461		- stop_ptraced_child(pid, stack, 1, 1);
	446	+ stop_ptraced_child(pid, 1, 1);
462	447	#else
463	448	/* PTRACE_LDT might be disabled via cmdline option.
464	449	* We want to override this, else we might use the stub