my code is having a bug here and i don't know how to fix it, so if you could please help me that'd be great.
Here's my code:
unsigned reverse(unsigned value)
{
unsigned res;
int l_mask, r_mask;
l_mask = 0x00000002, r_mask = 0x40000000;
for(res = 0; r_mask != 0x00000001; r_mask >>=1, l_mask <<= 1)
l_mask & value == 0 ? res &= ~r_mask : res |= r_mask;
return res;
}
The error is:
lvalue required as left operand of assignment
I've seen another posts and questions but nothing seems to be related to the problem that I'm having.
If anyone could help me I would be very appreciated
To fix this problem do that:
l_mask & value == 0 ? (res &= ~r_mask) : (res |= r_mask);
Precedence of the ternary condition (?:) is higher than |= and &=.
http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Operator_precedence
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 have small problem with adding and reading values.
Define variables
#define ADC_BIT_MASK 0x0FFF
static TaskHandle_t remoteControlTaskHandle = NULL;
typedef enum
{
...
rcEvent_FreshADC = 0x80000000,
...
}
Code for notify task. adc12bitVal_pedal value is for example 100 and adc12bitVal_lr value for example 1000. I am shifting adc12bitVal_lr to the left that I can pass params ...
static void remoteControl_FreshADC(uint16_t adc12bitVal_pedal, uint16_t adc12bitVal_lr)
{
if(remoteControlTaskHandle != NULL)
{
xTaskNotify(remoteControlTaskHandle,
(rcEvent_FreshADC | (adc12bitVal_pedal & ADC_BIT_MASK) | (adc12bitVal_lr & ADC_BIT_MASK)<<12),
eSetValueWithOverwrite);
}
}
and then remoteControlHandleEvent which handle an event. Here I have problem with adcVal_lr which should be 1000 but is for example 52123. I need to shift 12 to the left that I get correct value. Or this is wrong?
returnCode_t remoteControlHandleEvent(remoteControlEvent_t event)
{
if(event & rcEvent_motorControlACK)
{
uint8_t ackNum = (uint8_t) ( ((event >> MOTOR_CONTROL_ACK_BIT_POS) & MOTOR_CONTROL_ACK_BIT_MASK));
printf("CONF: %u\n", (unsigned int)ackNum);
}
if(event & rcEvent_FreshADC)
{
...
// Value is 100
uint16_t adcVal_pedal = (uint16_t)(event & ADC_BIT_MASK);
// DOESN'T WORK VALUE IS 52123 instead of 1000
uint16_t adcVal_lr = (uint16_t)((event & ADC_BIT_MASK)<<12);
...
}
}
I don't understand and know why wrong value for
uint16_t adcVal_lr = (uint16_t)((event & ADC_BIT_MASK)<<12);
Thnak you for all comments and help.
You are shifting left (up) twice. To extract a value that you shifted left you need to shift right (down). You also apply the mask before shifting, when it should be after.
uint16_t adcVal_lr = (uint16_t)((event >> 12) & ADC_BIT_MASK);
The question is specific to a pattern that Flawfinder reports:
The snippet
unsigned char child_report;
...
auto readlen = read(pipefd[0], (void *) &child_report, sizeof(child_report));
if(readlen == -1 || readlen != sizeof(child_report)) {
_ret.failure = execute_result::PREIO ; // set some flags to report to the caller
close(pipefd[0]);
return _ret;
}
...
int sec_read = read(pipefd[0], (void *) &child_report, sizeof(child_report));
child_report = 0; // we are not using the read data at all
// we just want to know if the read is successful or not
if (sec_read != 0 && sec_read != -1) { // if success
_ret.failure = execute_result::EXEC; // it means that the child is not able to exec
close(pipefd[0]); // as we set the close-on-exec flag
return _ret; // and we do write after exec in the child
}
I turned out that Codacy (therefore flawfinder) reports such issues on both read:
Check buffer boundaries if used in a loop including recursive loops (CWE-120, CWE-20).
I don't understand.
There is no loop.
In the second case we are not using the read data at all
This is not typical C string, and we don't rely on the ending '\0'
Is there any flaw that I'm not aware of in the code?
I finally conclude this should be a false positive. I check Flawfinder's code and it seems that it is basically doing pattern matching.
https://github.com/david-a-wheeler/flawfinder/blob/293ca17d8212905c7788aca1df7837d4716bd456/flawfinder#L1057
I am trying to write uint64_t(double word) variable into the flash memory, without success though. Here is the code.
#define APPLICATION_START_ADDRESS 0x8008000
void flashErase(uint8_t startSector, uint8_t numberOfSectors)
{
HAL_FLASH_Unlock();
Flash_eraseInitStruct.TypeErase = FLASH_TYPEERASE_SECTORS;
Flash_eraseInitStruct.VoltageRange = FLASH_VOLTAGE_RANGE_3;
Flash_eraseInitStruct.Sector = startSector;
Flash_eraseInitStruct.NbSectors = numberOfSectors;
if(HAL_FLASHEx_Erase(&Flash_eraseInitStruct, &Flash_halOperationSectorError) != HAL_OK)
{
Flash_raiseError(errHAL_FLASHEx_Erase);
}
HAL_FLASH_Lock();
}
int main(void)
{
HAL_Init();
main_clockSystemInit();
__IO uint64_t word = 0x1234567890;
flashErase(2, 1);
// flashProgramWord(aTxBuffer, APPLICATION_START_ADDRESS, 2 );
HAL_FLASH_Unlock();
HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, APPLICATION_START_ADDRESS, word);
}
I get error flag raised PGSERR and PGAERR. The erase operation goes without problems. But programming returns ERROR.
Some Ideas?
There is no STM32F249, did you mean STM32F429?
In order to use 64 bit programming, VPP (BOOT0) has to be powered by 8 - 9 Volts. Is it?
See the Reference Manual Section 3.6.2
By the way,
__IO uint64_t word = 0x1234567890;
would not work as (presumably) expected. It is a 32 bit architecture, integer constants will be truncated to 32 bits, unless there is an L suffix. U wouldn't hurt either, because the variable is unsigned. __IO is unnecessary.
uint64_t word = 0x1234567890UL;
I have written a function inside PostgreSQL which has the following code:
for (i = 0; i < 4; i++)
{
Datum dat_value = CStringGetDatum(inp->str[0][i]);
values[i] = datumCopy(dat_value,
stats->attrtype->typbyval,
stats->attrtype->typlen);
}
The input strings are {ALGERIA,ARGENTINA,BRAZIL,CANADA}. The code runs for ALGERIA,ARGENTINA but terminates abruptly for BRAZIL. When I investigated I found that inside datumCopy function, the statement after memcpy is not getting printed. I checked if palloc failed with (s == NULL) condition, but that seems to be not the reason. I think memcpy is failing. Any reason why? Thanks!
Datum
datumCopy(Datum value, bool typByVal, int typLen)
{
Datum res;
if (typByVal)
res = value;
else
{
Size realSize;
char *s;
if (DatumGetPointer(value) == NULL)
return PointerGetDatum(NULL);
realSize = datumGetSize(value, typByVal, typLen);
s = (char *) palloc(realSize);
printf ("Value : %s\n",DatumGetPointer(value));
memcpy(s, DatumGetPointer(value), realSize);
printf ("Not printing \n");
res = PointerGetDatum(s);
}
return res;
}
EDITED : Ok this is really wierd. When the input is one of {BRAZIL,PAKISTAN,FRANCE}, the code terminates abruptly. If I have other countries (I haven't tried extensively, but some countries), the code runs correctly.
EDITED 2 : Found the cause and rectified the issue. If we are passing C strings to datumCopy, we have to pass -2 for typLen parameter. I had been passing it incorrectly.
Thanks!
I have found the cause and rectified the issue.
If we are passing C strings to datumCopy, we have to pass -2 for typLen parameter. I had been passing it incorrectly.