Crash when memset of shared mapped memory in ARM

Crash when memset of shared mapped memory in ARM

[naveen yadav]

Hi All,

I am running below Test program on ARM cortex a9/a8 on kernel version
2.6.35.14 as well as on 3.0.

Please find the test case where:

1. Create shared memory object using shm_open(If we use normal open
then no problem only problem with shm_open)

2. ftruncate to given size

3. memory map the shared object to given memory address ( I haved
tested without MAP_SHARED, MAP_FIXED as well, problem exist)

4. Memset the shared memory (got page fault when accessing the second page)




Observation: Only observed in ARM ( i.e not present in MIPS and X86)


#undef NDEBUG
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <errno.h>
#include <pthread.h>
#include <string.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>

enum {
 SHM_INIT,
 SHM_GET
 };

enum {
 PARENT,
 CHILD
 };

#define FIXED_MMAP_ADDR 0x20000000
#define MMAP_SIZE	0x10000

static int shmid;
static char shm_name[100];
static int sleep_period = 100000;
void * shmem_init(int flag)
{	
	int start = FIXED_MMAP_ADDR;
	int memory_size = MMAP_SIZE;
	int mode = 0666;
	void *addr;
	int ret;
	sprintf(shm_name, "/shmem_1234");
	shmid = shm_open (shm_name, O_RDWR | O_EXCL | O_CREAT | O_TRUNC, mode);
	if (shmid < 0) {
    		if (errno == EEXIST) {
			printf ("shm_open: %s\n", strerror(errno));
       			shmid = shm_open (shm_name, O_RDWR, mode);

		} else {
    			printf("failed to shm_open, err=%s\n", strerror(errno));
			return NULL;
  		}
	}
  	ret = fcntl (shmid, F_SETFD, FD_CLOEXEC);
  	if (ret < 0) {
    		printf("fcntl: %s\n", strerror(errno));
		return NULL;
  	}
	ret = ftruncate (shmid, memory_size);
	if (ret < 0) {
    		printf("ftruncate: %s\n", strerror(errno));
		return NULL;
  	}
	addr = mmap ((void *)start, memory_size, PROT_READ | PROT_WRITE,
 			     MAP_SHARED | MAP_FIXED, shmid, 0);
  	if (addr == MAP_FAILED) {
		printf ("mmap: %s\n", strerror(errno));
     		close (shmid);
    		shm_unlink (shm_name);
		return NULL;
	}
	
	if (flag == SHM_INIT){
		printf ("mmap: addr %p\n", addr);
		/* memset on arm creates a unhandled page fault, works fine on mips */
		memset(addr, 0, memory_size);
	}
	return (void *)addr;
}

pthread_mutex_t * shmem_mutex_init(int flag)
{
	pthread_mutex_t * pmutex = (pthread_mutex_t *)shmem_init(flag);
#if 0
	pthread_mutexattr_t attr;
	if (flag == SHM_INIT) {
		pthread_mutexattr_init (&attr);
		pthread_mutexattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
		pthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT);
		pthread_mutexattr_setrobust_np (&attr,
 						PTHREAD_MUTEX_STALLED_NP);
		pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
		if (pthread_mutex_init (pmutex, &attr) != 0) {
    			printf("Init mutex failed, err=%s\n", strerror(errno));
			pthread_mutexattr_destroy (&attr);
			return NULL;
		}
	}
#endif
	return pmutex;
}

void long_running_task(int flag)
{	
	static int counter = 0;
	if (flag == PARENT)
 		usleep(5*sleep_period);
	else
		usleep(3*sleep_period);
	counter = (counter + 1) % 100;
	printf("%d: completed %d computing\n", getpid(), counter);
}

void sig_handler(int signum)
{
	close(shmid);
	shm_unlink(shm_name);
	exit(0);
}

int main(int argc, char *argv[])
{
	pthread_mutex_t *mutex_parent, *mutex_child;
//	signal(SIGUSR1, sig_handler);
//	if (fork()) {
		/* parent process */
		if ((mutex_parent = shmem_mutex_init(SHM_INIT)) == NULL) {
			printf("failed to get the shmem_mutex\n");
			exit(-1);
		}
#if 0
		while (1) {
			printf("%d: try to hold the lock\n", getpid());
 			pthread_mutex_lock(mutex_parent);
			printf("%d: got the lock\n", getpid());
 			long_running_task(PARENT);
			pthread_mutex_unlock(mutex_parent);
			printf("%d: released the lock\n", getpid());
		}
#endif
//	} else {
#if 0
		/* child process */
		usleep(sleep_period);
		if ((mutex_child = shmem_mutex_init(SHM_GET)) == NULL) {
			printf("failed to get the shmem_mutex\n");
			exit(-1);
		}
		while (1) {
			printf("%d: try to hold the lock\n", getpid());
 			pthread_mutex_lock(mutex_child);
			printf("%d: got the lock\n", getpid());
 			long_running_task(CHILD);
			pthread_mutex_unlock(mutex_child);
			printf("%d: released the lock\n", getpid());
		}
#endif
//	}
	return 0;
}

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Re: Crash when memset of shared mapped memory in ARM

[Russell King - ARM Linux]

On Wed, Nov 16, 2011 at 11:05:49AM +0530, naveen yadav wrote:
> Hi All,
> 
> I am running below Test program on ARM cortex a9/a8 on kernel version
> 2.6.35.14 as well as on 3.0.
> 
> Please find the test case where:
> 
> 1. Create shared memory object using shm_open(If we use normal open
> then no problem only problem with shm_open)
> 
> 2. ftruncate to given size
> 
> 3. memory map the shared object to given memory address ( I haved
> tested without MAP_SHARED, MAP_FIXED as well, problem exist)
> 
> 4. Memset the shared memory (got page fault when accessing the second page)
> 
> 
> 
> 
> Observation: Only observed in ARM ( i.e not present in MIPS and X86)

Yes, so, what happens?

> 
> 
> #undef NDEBUG
> #define _GNU_SOURCE
> #include <unistd.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/ipc.h>
> #include <sys/shm.h>
> #include <errno.h>
> #include <pthread.h>
> #include <string.h>
> #include <signal.h>
> #include <fcntl.h>
> #include <sys/types.h>
> #include <sys/mman.h>
> 
> enum {
>  SHM_INIT,
>  SHM_GET
>  };
> 
> enum {
>  PARENT,
>  CHILD
>  };
> 
> #define FIXED_MMAP_ADDR 0x20000000
> #define MMAP_SIZE	0x10000
> 
> static int shmid;
> static char shm_name[100];
> static int sleep_period = 100000;
> void * shmem_init(int flag)
> {	
> 	int start = FIXED_MMAP_ADDR;
> 	int memory_size = MMAP_SIZE;
> 	int mode = 0666;
> 	void *addr;
> 	int ret;
> 	sprintf(shm_name, "/shmem_1234");
> 	shmid = shm_open (shm_name, O_RDWR | O_EXCL | O_CREAT | O_TRUNC, mode);
> 	if (shmid < 0) {
>     		if (errno == EEXIST) {
> 			printf ("shm_open: %s\n", strerror(errno));
>        			shmid = shm_open (shm_name, O_RDWR, mode);
> 
> 		} else {
>     			printf("failed to shm_open, err=%s\n", strerror(errno));
> 			return NULL;
>   		}
> 	}
>   	ret = fcntl (shmid, F_SETFD, FD_CLOEXEC);
>   	if (ret < 0) {
>     		printf("fcntl: %s\n", strerror(errno));
> 		return NULL;
>   	}
> 	ret = ftruncate (shmid, memory_size);
> 	if (ret < 0) {
>     		printf("ftruncate: %s\n", strerror(errno));
> 		return NULL;
>   	}
> 	addr = mmap ((void *)start, memory_size, PROT_READ | PROT_WRITE,
>  			     MAP_SHARED | MAP_FIXED, shmid, 0);
>   	if (addr == MAP_FAILED) {
> 		printf ("mmap: %s\n", strerror(errno));
>      		close (shmid);
>     		shm_unlink (shm_name);
> 		return NULL;
> 	}
> 	
> 	if (flag == SHM_INIT){
> 		printf ("mmap: addr %p\n", addr);
> 		/* memset on arm creates a unhandled page fault, works fine on mips */
> 		memset(addr, 0, memory_size);
> 	}
> 	return (void *)addr;
> }
> 
> pthread_mutex_t * shmem_mutex_init(int flag)
> {
> 	pthread_mutex_t * pmutex = (pthread_mutex_t *)shmem_init(flag);
> #if 0
> 	pthread_mutexattr_t attr;
> 	if (flag == SHM_INIT) {
> 		pthread_mutexattr_init (&attr);
> 		pthread_mutexattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
> 		pthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT);
> 		pthread_mutexattr_setrobust_np (&attr,
>  						PTHREAD_MUTEX_STALLED_NP);
> 		pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
> 		if (pthread_mutex_init (pmutex, &attr) != 0) {
>     			printf("Init mutex failed, err=%s\n", strerror(errno));
> 			pthread_mutexattr_destroy (&attr);
> 			return NULL;
> 		}
> 	}
> #endif
> 	return pmutex;
> }
> 
> void long_running_task(int flag)
> {	
> 	static int counter = 0;
> 	if (flag == PARENT)
>  		usleep(5*sleep_period);
> 	else
> 		usleep(3*sleep_period);
> 	counter = (counter + 1) % 100;
> 	printf("%d: completed %d computing\n", getpid(), counter);
> }
> 
> void sig_handler(int signum)
> {
> 	close(shmid);
> 	shm_unlink(shm_name);
> 	exit(0);
> }
> 
> int main(int argc, char *argv[])
> {
> 	pthread_mutex_t *mutex_parent, *mutex_child;
> //	signal(SIGUSR1, sig_handler);
> //	if (fork()) {
> 		/* parent process */
> 		if ((mutex_parent = shmem_mutex_init(SHM_INIT)) == NULL) {
> 			printf("failed to get the shmem_mutex\n");
> 			exit(-1);
> 		}
> #if 0
> 		while (1) {
> 			printf("%d: try to hold the lock\n", getpid());
>  			pthread_mutex_lock(mutex_parent);
> 			printf("%d: got the lock\n", getpid());
>  			long_running_task(PARENT);
> 			pthread_mutex_unlock(mutex_parent);
> 			printf("%d: released the lock\n", getpid());
> 		}
> #endif
> //	} else {
> #if 0
> 		/* child process */
> 		usleep(sleep_period);
> 		if ((mutex_child = shmem_mutex_init(SHM_GET)) == NULL) {
> 			printf("failed to get the shmem_mutex\n");
> 			exit(-1);
> 		}
> 		while (1) {
> 			printf("%d: try to hold the lock\n", getpid());
>  			pthread_mutex_lock(mutex_child);
> 			printf("%d: got the lock\n", getpid());
>  			long_running_task(CHILD);
> 			pthread_mutex_unlock(mutex_child);
> 			printf("%d: released the lock\n", getpid());
> 		}
> #endif
> //	}
> 	return 0;
> }

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Re: Crash when memset of shared mapped memory in ARM

[Russell King - ARM Linux]

Please do not spam mailing lists -request addresses when you post.  The
-request addresses are there for you to give the mailing list software
_instructions_ on what to do with your subscription.  It is not for
posts to the mailing list.

Thanks.

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Re: Crash when memset of shared mapped memory in ARM

[naveen yadav]

Ok,
On X86, MIPS
#./tc1
mmap: addr 0x20000000
#
#

On ARM (2.6.35.11 ~ 3.0.2)
#tc1
map: addr 0x20000000
tc1: unhandled page fault (7) at 0x20001000, code 0x817
Bus error (core dumped)
#
#
Debug Information
Pid: 179, comm:                  tc1
CPU: 0    Not tainted  (2.6.35.11 #1)
PC is at 0x400da410
LR is at 0x8858
pc : [<400da410>]    lr : [<00008858>]    psr: 20000010
sp : bed84814  ip : 20001080  fp : 00000000
r10: 40025000  r9 : 00000000  r8 : 00000000
r7 : 20000000  r6 : 20001000  r5 : 00000000  r4 : 0000ef80
r3 : 00000000  r2 : 20010000  r1 : 00000000  r0 : 20000000
Flags: nzCv  IRQs on  FIQs on  Mode USER_32  ISA ARM  Segment user

Process Memory map
00008000-00009000 r-xp 00000000 08:01 153 /usb/sda1/tc1
00010000-00011000 rw-p 00000000 08:01 153 /usb/sda1/tc1
00011000-00032000 rw-p 00011000 08:01 153
20000000-20010000 rw-s 00000000 00:0d 249 /dev/shm/shmem_1234
40000000-4001d000 r-xp 00000000 8b:06 163 /lib/ld-2.11.1.so
4001d000-40021000 rw-p 4001d000 8b:06 163
40024000-40025000 r--p 0001c000 8b:06 163 /lib/ld-2.11.1.so
40025000-40026000 rw-p 0001d000 8b:06 163 /lib/ld-2.11.1.so
40026000-4003b000 r-xp 00000000 8b:06 171 /lib/libpthread-2.11.1.so
4003b000-40042000 ---p 00015000 8b:06 171 /lib/libpthread-2.11.1.so
40042000-40043000 r--p 00014000 8b:06 171 /lib/libpthread-2.11.1.so
40043000-40044000 rw-p 00015000 8b:06 171 /lib/libpthread-2.11.1.so
40044000-40046000 rw-p 40044000 8b:06 171
40046000-4004c000 r-xp 00000000 8b:06 161 /lib/librt-2.11.1.so
4004c000-40053000 ---p 00006000 8b:06 161 /lib/librt-2.11.1.so
40053000-40054000 r--p 00005000 8b:06 161 /lib/librt-2.11.1.so
40054000-40055000 rw-p 00006000 8b:06 161 /lib/librt-2.11.1.so
40055000-4005f000 r-xp 00000000 8b:06 165 /lib/libgcc_s.so.1
4005f000-40067000 ---p 0000a000 8b:06 165 /lib/libgcc_s.so.1
40067000-40068000 rw-p 0000a000 8b:06 165 /lib/libgcc_s.so.1
40068000-40185000 r-xp 00000000 8b:06 174 /lib/libc-2.11.1.so
40185000-4018d000 ---p 0011d000 8b:06 174 /lib/libc-2.11.1.so
4018d000-4018f000 r--p 0011d000 8b:06 174 /lib/libc-2.11.1.so
4018f000-40190000 rw-p 0011f000 8b:06 174 /lib/libc-2.11.1.so
40190000-40193000 rw-p 40190000 8b:06 174
bed63000-bed85000 rw-p befde000 8b:06 174

We wish to know why the same application crashes on ARM ?
On Wed, Nov 16, 2011 at 1:57 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Wed, Nov 16, 2011 at 11:05:49AM +0530, naveen yadav wrote:
>> Hi All,
>>
>> I am running below Test program on ARM cortex a9/a8 on kernel version
>> 2.6.35.14 as well as on 3.0.
>>
>> Please find the test case where:
>>
>> 1. Create shared memory object using shm_open(If we use normal open
>> then no problem only problem with shm_open)
>>
>> 2. ftruncate to given size
>>
>> 3. memory map the shared object to given memory address ( I haved
>> tested without MAP_SHARED, MAP_FIXED as well, problem exist)
>>
>> 4. Memset the shared memory (got page fault when accessing the second page)
>>
>>
>>
>>
>> Observation: Only observed in ARM ( i.e not present in MIPS and X86)
>
> Yes, so, what happens?
>
>>
>>
>> #undef NDEBUG
>> #define _GNU_SOURCE
>> #include <unistd.h>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <sys/ipc.h>
>> #include <sys/shm.h>
>> #include <errno.h>
>> #include <pthread.h>
>> #include <string.h>
>> #include <signal.h>
>> #include <fcntl.h>
>> #include <sys/types.h>
>> #include <sys/mman.h>
>>
>> enum {
>>  SHM_INIT,
>>  SHM_GET
>>  };
>>
>> enum {
>>  PARENT,
>>  CHILD
>>  };
>>
>> #define FIXED_MMAP_ADDR 0x20000000
>> #define MMAP_SIZE     0x10000
>>
>> static int shmid;
>> static char shm_name[100];
>> static int sleep_period = 100000;
>> void * shmem_init(int flag)
>> {
>>       int start = FIXED_MMAP_ADDR;
>>       int memory_size = MMAP_SIZE;
>>       int mode = 0666;
>>       void *addr;
>>       int ret;
>>       sprintf(shm_name, "/shmem_1234");
>>       shmid = shm_open (shm_name, O_RDWR | O_EXCL | O_CREAT | O_TRUNC, mode);
>>       if (shmid < 0) {
>>               if (errno == EEXIST) {
>>                       printf ("shm_open: %s\n", strerror(errno));
>>                               shmid = shm_open (shm_name, O_RDWR, mode);
>>
>>               } else {
>>                       printf("failed to shm_open, err=%s\n", strerror(errno));
>>                       return NULL;
>>               }
>>       }
>>       ret = fcntl (shmid, F_SETFD, FD_CLOEXEC);
>>       if (ret < 0) {
>>               printf("fcntl: %s\n", strerror(errno));
>>               return NULL;
>>       }
>>       ret = ftruncate (shmid, memory_size);
>>       if (ret < 0) {
>>               printf("ftruncate: %s\n", strerror(errno));
>>               return NULL;
>>       }
>>       addr = mmap ((void *)start, memory_size, PROT_READ | PROT_WRITE,
>>                            MAP_SHARED | MAP_FIXED, shmid, 0);
>>       if (addr == MAP_FAILED) {
>>               printf ("mmap: %s\n", strerror(errno));
>>               close (shmid);
>>               shm_unlink (shm_name);
>>               return NULL;
>>       }
>>
>>       if (flag == SHM_INIT){
>>               printf ("mmap: addr %p\n", addr);
>>               /* memset on arm creates a unhandled page fault, works fine on mips */
>>               memset(addr, 0, memory_size);
>>       }
>>       return (void *)addr;
>> }
>>
>> pthread_mutex_t * shmem_mutex_init(int flag)
>> {
>>       pthread_mutex_t * pmutex = (pthread_mutex_t *)shmem_init(flag);
>> #if 0
>>       pthread_mutexattr_t attr;
>>       if (flag == SHM_INIT) {
>>               pthread_mutexattr_init (&attr);
>>               pthread_mutexattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
>>               pthread_mutexattr_setprotocol (&attr, PTHREAD_PRIO_INHERIT);
>>               pthread_mutexattr_setrobust_np (&attr,
>>                                               PTHREAD_MUTEX_STALLED_NP);
>>               pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
>>               if (pthread_mutex_init (pmutex, &attr) != 0) {
>>                       printf("Init mutex failed, err=%s\n", strerror(errno));
>>                       pthread_mutexattr_destroy (&attr);
>>                       return NULL;
>>               }
>>       }
>> #endif
>>       return pmutex;
>> }
>>
>> void long_running_task(int flag)
>> {
>>       static int counter = 0;
>>       if (flag == PARENT)
>>               usleep(5*sleep_period);
>>       else
>>               usleep(3*sleep_period);
>>       counter = (counter + 1) % 100;
>>       printf("%d: completed %d computing\n", getpid(), counter);
>> }
>>
>> void sig_handler(int signum)
>> {
>>       close(shmid);
>>       shm_unlink(shm_name);
>>       exit(0);
>> }
>>
>> int main(int argc, char *argv[])
>> {
>>       pthread_mutex_t *mutex_parent, *mutex_child;
>> //    signal(SIGUSR1, sig_handler);
>> //    if (fork()) {
>>               /* parent process */
>>               if ((mutex_parent = shmem_mutex_init(SHM_INIT)) == NULL) {
>>                       printf("failed to get the shmem_mutex\n");
>>                       exit(-1);
>>               }
>> #if 0
>>               while (1) {
>>                       printf("%d: try to hold the lock\n", getpid());
>>                       pthread_mutex_lock(mutex_parent);
>>                       printf("%d: got the lock\n", getpid());
>>                       long_running_task(PARENT);
>>                       pthread_mutex_unlock(mutex_parent);
>>                       printf("%d: released the lock\n", getpid());
>>               }
>> #endif
>> //    } else {
>> #if 0
>>               /* child process */
>>               usleep(sleep_period);
>>               if ((mutex_child = shmem_mutex_init(SHM_GET)) == NULL) {
>>                       printf("failed to get the shmem_mutex\n");
>>                       exit(-1);
>>               }
>>               while (1) {
>>                       printf("%d: try to hold the lock\n", getpid());
>>                       pthread_mutex_lock(mutex_child);
>>                       printf("%d: got the lock\n", getpid());
>>                       long_running_task(CHILD);
>>                       pthread_mutex_unlock(mutex_child);
>>                       printf("%d: released the lock\n", getpid());
>>               }
>> #endif
>> //    }
>>       return 0;
>> }
>

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Re: Crash when memset of shared mapped memory in ARM

[Will Deacon]

(Replying to Russell so as to lose the -request addresses)

On Wed, Nov 16, 2011 at 08:45:47AM +0000, Russell King - ARM Linux wrote:
> Please do not spam mailing lists -request addresses when you post.  The
> -request addresses are there for you to give the mailing list software
> _instructions_ on what to do with your subscription.  It is not for
> posts to the mailing list.

For what it's worth, I was brave/daft enough to compile and run the testcase
with an -rc1 kernel and Linaro 11.09 filesystem on the quad A9 Versatile
Express:

root@dancing-fool:~# ./yad
mmap: addr 0x20000000
root@dancing-fool:~# ./yad
shm_open: File exists
mmap: addr 0x20000000

Looks like I'm missing the fireworks, despite the weirdy MAP_SHARED |
MAP_FIXED mmap flags.

Will

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Re: Crash when memset of shared mapped memory in ARM

[Dave Martin]

On Wed, Nov 16, 2011 at 11:54:35AM +0000, Will Deacon wrote:
> (Replying to Russell so as to lose the -request addresses)
> 
> On Wed, Nov 16, 2011 at 08:45:47AM +0000, Russell King - ARM Linux wrote:
> > Please do not spam mailing lists -request addresses when you post.  The
> > -request addresses are there for you to give the mailing list software
> > _instructions_ on what to do with your subscription.  It is not for
> > posts to the mailing list.
> 
> For what it's worth, I was brave/daft enough to compile and run the testcase
> with an -rc1 kernel and Linaro 11.09 filesystem on the quad A9 Versatile
> Express:
> 
> root@dancing-fool:~# ./yad
> mmap: addr 0x20000000
> root@dancing-fool:~# ./yad
> shm_open: File exists
> mmap: addr 0x20000000
> 
> Looks like I'm missing the fireworks, despite the weirdy MAP_SHARED |
> MAP_FIXED mmap flags.

I did't see any problem on a random 3.1-rc4 kernel either on A9...

(Since when was MAP_SHARED "weirdy"...?)

Cheers
---Dave

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