I am reading the code about the implementation of printing stack trace in native code of android, I found the following code:
ssize_t unwind_backtrace(backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
ALOGV("Unwinding current thread %d.", gettid());
map_info_t* milist = acquire_my_map_info_list();
backtrace_state_t state;
state.backtrace = backtrace;
state.ignore_depth = ignore_depth;
state.max_depth = max_depth;
state.ignored_frames = 0;
state.returned_frames = 0;
init_memory(&state.memory, milist);
_Unwind_Reason_Code rc = _Unwind_Backtrace(unwind_backtrace_callback, &state);
release_my_map_info_list(milist);
if (state.returned_frames) {
return state.returned_frames;
}
return rc == _URC_END_OF_STACK ? 0 : -1;
}
but I can't find the implementation of _Unwind_Backtrace in http://androidxref.com/4.4.2_r2/ , is there any body konw the reason? Where is the implementation of _Unwind_Backtrace?
For android 4.4, unwind_backtrace is in /system/core/libcorkscrew/backtrace.c
Related
I have an example program I am running here to see if the substring matches the string and then print them out. So far, I am having trouble running the program due to a bad address. I am wondering if there is a way to fix this problem? I have attached the entire code but my problem is mostly related to isSubstring.
#include <uapi/linux/bpf.h>
#define ARRAYSIZE 64
struct data_t {
char buf[ARRAYSIZE];
};
BPF_ARRAY(lookupTable, struct data_t, ARRAYSIZE);
//char name[20];
//find substring in a string
static bool isSubstring(struct data_t stringVal)
{
char substring[] = "New York";
int M = sizeof(substring);
int N = sizeof(stringVal.buf) - 1;
/* A loop to slide pat[] one by one */
for (int i = 0; i <= N - M; i++) {
int j;
/* For current index i, check for
pattern match */
for (j = 0; j < M; j++)
if (stringVal.buf[i + j] != substring[j])
break;
if (j == M)
return true;
}
return false;
}
int Test(void *ctx)
{
#pragma clang loop unroll(full)
for (int i = 0; i < ARRAYSIZE; i++) {
int k = i;
struct data_t *line = lookupTable.lookup(&k);
if (line) {
// bpf_trace_printk("%s\n", key->buf);
if (isSubstring(*line)) {
bpf_trace_printk("%s\n", line->buf);
}
}
}
return 0;
}
My python code here:
import ctypes
from bcc import BPF
b = BPF(src_file="hello.c")
lookupTable = b["lookupTable"]
#add hello.csv to the lookupTable array
f = open("hello.csv","r")
contents = f.readlines()
for i in range(0,len(contents)):
string = contents[i].encode('utf-8')
print(len(string))
lookupTable[ctypes.c_int(i)] = ctypes.create_string_buffer(string, len(string))
f.close()
b.attach_kprobe(event=b.get_syscall_fnname("clone"), fn_name="Test")
b.trace_print()
Edit: Forgot to add the error: It's really long and can be found here: https://pastebin.com/a7E9L230
I think the most interesting part of the error is near the bottom where it mentions:
The sequence of 8193 jumps is too complex.
And a little bit farther down mentions: Bad Address.
The verifier checks all branches in your program. Each time it sees a jump instruction, it pushes the new branch to its “stack of branches to check”. This stack has a limit (BPF_COMPLEXITY_LIMIT_JMP_SEQ, currently 8192) that you are hitting, as the verifier tells you. “Bad Address” is just the translation of kernel's errno value which is set to -EFAULT in that case.
Not sure how to fix it though, you could try:
With smaller strings, or
On a 5.3+ kernel (which supports bounded loops): without unrolling the loop with clang (I don't know if it would help).
I am working on STM32F4 board. My IDE is IAR Embedded Work bench. I am trying to do a software reset from code. For that i used API ' NVIC_SystemReset(); ' defined in
core_cm4.h header. But the system reset is not happening.
I tried the same thing in STM32F3, same IDE . I used the function NVIC_SystemReset(); from core_sc300.h header. Using that software reset is happening. I found the definition of functions in both file are same and both controllers are Cortex M4 only.What is the problem with STM32F4 board.? Can any one help me in solving this or can any one suggest an alternative way for system reset in STM32F4.
Please help.
Thanks in advance
In the HAL You can use
HAL_NVIC_SystemReset();
You can use a watch-dog instead:
Call wdg_activate(n) in order to initiate system-reset within n milliseconds
Call wdg_reactivate() in order to reload the counter back to n milliseconds
void wdg_activate(unsigned short num_of_ms)
{
uint8_t prescale_reg;
uint8_t prescale_val;
if (num_of_ms < 1)
{
num_of_ms = 1;
prescale_reg = IWDG_Prescaler_32;
prescale_val = 1;
}
else if (num_of_ms <= 4096)
{
prescale_reg = IWDG_Prescaler_32;
prescale_val = 1;
}
else if (num_of_ms <= 8192)
{
prescale_reg = IWDG_Prescaler_64;
prescale_val = 2;
}
else if (num_of_ms <= 16384)
{
prescale_reg = IWDG_Prescaler_128;
prescale_val = 4;
}
else if (num_of_ms <= 32768)
{
prescale_reg = IWDG_Prescaler_256;
prescale_val = 8;
}
else
{
num_of_ms = 32768;
prescale_reg = IWDG_Prescaler_256;
prescale_val = 8;
}
IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);
while (IWDG_GetFlagStatus(IWDG_FLAG_PVU));
IWDG_SetPrescaler(prescale_reg);
while (IWDG_GetFlagStatus(IWDG_FLAG_RVU));
IWDG_SetReload(num_of_ms/prescale_val-1);
IWDG_Enable();
}
void wdg_reactivate()
{
IWDG_ReloadCounter();
}
There have been several iterations of NVIC_SystemReset(). Please post the code for the version you are using. The current [working STM32F4] version that I am using is as follows:
/** \brief System Reset
The function initiates a system reset request to reset the MCU.
*/
__STATIC_INLINE void NVIC_SystemReset(void)
{
__DSB(); /* Ensure all outstanding memory accesses included
buffered write are completed before reset */
SCB->AIRCR = ((0x5FA << SCB_AIRCR_VECTKEY_Pos) |
(SCB->AIRCR & SCB_AIRCR_PRIGROUP_Msk) |
SCB_AIRCR_SYSRESETREQ_Msk); /* Keep priority group unchanged */
__DSB(); /* Ensure completion of memory access */
while(1); /* wait until reset */
}
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/sem.h>
#include<sys/ipc.h>
int sem_id;
void update_file(int number)
{
struct sembuf sem_op;
FILE* file;
printf("Inside Update Process\n");
/* wait on the semaphore, unless it's value is non-negative. */
sem_op.sem_num = 0;
sem_op.sem_op = -1; /* <-- Amount by which the value of the semaphore is to be decreased */
sem_op.sem_flg = 0;
semop(sem_id, &sem_op, 1);
/* we "locked" the semaphore, and are assured exclusive access to file. */
/* manipulate the file in some way. for example, write a number into it. */
file = fopen("file.txt", "a+");
if (file) {
fprintf(file, " \n%d\n", number);
fclose(file);
}
/* finally, signal the semaphore - increase its value by one. */
sem_op.sem_num = 0;
sem_op.sem_op = 1;
sem_op.sem_flg = 0;
semop( sem_id, &sem_op, 1);
}
void write_file(char* contents)
{
printf("Inside Write Process\n");
struct sembuf sem_op;
sem_op.sem_num = 0;
sem_op.sem_op = -1;
sem_op.sem_flg = 0;
semop( sem_id, &sem_op, 1);
FILE *file = fopen("file.txt","w");
if(file)
{
fprintf(file,contents);
fclose(file);
}
sem_op.sem_num = 0;
sem_op.sem_op = 1;
sem_op.sem_flg = 0;
semop( sem_id, &sem_op, 1);
}
int main()
{
//key_t key = ftok("file.txt",'E');
sem_id = semget( IPC_PRIVATE, 1, 0600 | IPC_CREAT);
/*here 100 is any arbit number to be assigned as the key of the
semaphore,1 is the number of semaphores in the semaphore set, */
if(sem_id == -1)
{
perror("main : semget");
exit(1);
}
int rc = semctl( sem_id, 0, SETVAL, 1);
pid_t u = fork();
if(u == 0)
{
update_file(100);
exit(0);
}
else
{
wait();
}
pid_t w = fork();
if(w == 0)
{
write_file("Hello!!");
exit(0);
}
else
{
wait();
}
}
If I run the above code as a c code, the write_file() function is called after the update_file () function
Whereas if I run the same code as a c++ code, the order of execution is reverse... why is it so??
Just some suggestions, but it looks to me like it could be caused by a combination of things:
The wait() call is supposed to take a pointer argument (that can
be NULL). Compiler should have caught this, but you must be picking
up another definition somewhere that permits your syntax. You are
also missing an include for sys/wait.h. This might be why the
compiler isn't complaining as I'd expect it to.
Depending on your machine/OS configuration the fork'd process may
not get to run until after the parent yields. Assuming the "wait()"
you are calling isn't working the way we would be expecting, it is
possible for the parent to execute completely before the children
get to run.
Unfortunately, I wasn't able to duplicate the same temporal behavior. However, when I generated assembly files for each of the two cases (C & C++), I noticed that the C++ version is missing the "wait" system call, but the C version is as I would expect. To me, this suggests that somewhere in the C++ headers this special version without an argument is being #defined out of the code. This difference could be the reason behind the behavior you are seeing.
In a nutshell... add the #include, and change your wait calls to "wait(0)"
Reading the documentation about iOS SDK CMBufferQueueCreate, it says that getDuration and version are required, all the others callbacks can be NULL.
But running the following code:
CFAllocatorRef allocator;
CMBufferCallbacks *callbacks;
callbacks = malloc(sizeof(CMBufferCallbacks));
callbacks->version = 0;
callbacks->getDuration = timeCallback;
callbacks->refcon = NULL;
callbacks->getDecodeTimeStamp = NULL;
callbacks->getPresentationTimeStamp = NULL;
callbacks->isDataReady = NULL;
callbacks->compare = NULL;
callbacks->dataBecameReadyNotification = NULL;
CMItemCount capacity = 4;
OSStatus s = CMBufferQueueCreate(allocator, capacity, callbacks, queue);
NSLog(#"QUEUE: %x", queue);
NSLog(#"STATUS: %i", s);
with timeCallback:
CMTime timeCallback(CMBufferRef buf, void *refcon){
return CMTimeMake(1, 1);
}
and queue is:
CMBufferQueueRef* queue;
queue creations fails (queue = 0) and returns a status of:
kCMBufferQueueError_RequiredParameterMissing = -12761,
The callbacks variable is correctly initialized, at least the debugger says so.
Has anybody used the CMBufferQueue?
Presumably there is nothing wrong with the parameters. At least the same as what you wrote is stated in CMBufferQueue.h about the required parameters. But it looks like you are passing a null pointer as the CMBufferQueueRef* parameter. I have updated your sample as follows and it seems to create the message loop OK.
CMBufferQueueRef queue;
CFAllocatorRef allocator = kCFAllocatorDefault;
CMBufferCallbacks *callbacks;
callbacks = malloc(sizeof(CMBufferCallbacks));
callbacks->version = 0;
callbacks->getDuration = timeCallback;
callbacks->refcon = NULL;
callbacks->getDecodeTimeStamp = NULL;
callbacks->getPresentationTimeStamp = NULL;
callbacks->isDataReady = NULL;
callbacks->compare = NULL;
callbacks->dataBecameReadyNotification = NULL;
CMItemCount capacity = 4;
OSStatus s = CMBufferQueueCreate(allocator, capacity, callbacks, &queue);
NSLog(#"QUEUE: %x", queue);
NSLog(#"STATUS: %i", s);
The time callback is still the same.
It does not look like it helps topic starter, but I hope it helps somebody else.
I'm trying to get audio queue working on an iphone app, and whenever AudioQueueStart is called it gives the "fmt?" result code (kAudioFormatUnsupportedDataFormatError). In the code below i'm setting the format to kAudioFormatLinearPCM, which surely is supported. What am i doing wrong?
data.mDataFormat.mSampleRate = 44100;
data.mDataFormat.mFormatID = kAudioFormatLinearPCM;
data.mDataFormat.mFormatFlags = 0;
data.mDataFormat.mBytesPerPacket = 4;
data.mDataFormat.mFramesPerPacket = 1;
data.mDataFormat.mBytesPerFrame = 4;
data.mDataFormat.mChannelsPerFrame = 2;
data.mDataFormat.mBitsPerChannel = 16;
OSStatus status;
status = AudioQueueNewOutput(&data.mDataFormat, audioCallback, &data, CFRunLoopGetCurrent (), kCFRunLoopCommonModes, 0, &data.mQueue);
for (int i = 0; i < NUMBUFFERS; ++i)
{
status = AudioQueueAllocateBuffer (data.mQueue, BUFFERSIZE, &data.mBuffers[i] );
audioCallback (&data, data.mQueue, data.mBuffers[i]);
}
Float32 gain = 1.0;
status = AudioQueueSetParameter (data.mQueue, kAudioQueueParam_Volume, gain);
status = AudioQueueStart(data.mQueue, NULL);
data is of type audioData which is like this:
typedef struct _audioData {
AudioQueueRef mQueue;
AudioQueueBufferRef mBuffers[NUMBUFFERS];
AudioStreamBasicDescription mDataFormat;
} audioData;
thanks
The cause of your error is actually AudioQueueNewOutput rather than AudioQueueStart.. See this related question audio streaming services failing to recognize file type
it turns out i needed to set some flags. it works with
data.mDataFormat.mFormatFlags = kLinearPCMFormatFlagIsBigEndian | kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
edit: actually, dont use kLinearPCMFormatFlagIsBigEndian, it seems that with this format it should be little endian.