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Add xReadfile wrapper for reading small to medium size files

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Inspired by proposed Linux syscall

Avoid file descriptor leaks like 4af8c63f
This commit is contained in:
Christian Göttsche
2020-11-25 12:42:36 +01:00
committed by BenBE
parent 1d8192c10b
commit f7a8952933
5 changed files with 85 additions and 134 deletions
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93
linux/LinuxProcessList.c
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@ -58,29 +58,6 @@ in the source distribution for its full text.
#endif
static ssize_t xread(int fd, void* buf, size_t count) {
// Read some bytes. Retry on EINTR and when we don't get as many bytes as we requested.
size_t alreadyRead = 0;
for (;;) {
ssize_t res = read(fd, buf, count);
if (res == -1) {
if (errno == EINTR)
continue;
return -1;
}
if (res > 0) {
buf = ((char*)buf) + res;
count -= res;
alreadyRead += res;
}
if (count == 0 || res == 0) {
return alreadyRead;
}
}
}
static FILE* fopenat(openat_arg_t openatArg, const char* pathname, const char* mode) {
assert(String_eq(mode, "r")); /* only currently supported mode */
@ -108,28 +85,12 @@ static int sortTtyDrivers(const void* va, const void* vb) {
static void LinuxProcessList_initTtyDrivers(LinuxProcessList* this) {
TtyDriver* ttyDrivers;
int fd = open(PROCTTYDRIVERSFILE, O_RDONLY);
if (fd == -1)
char buf[16384];
ssize_t r = xReadfile(PROCTTYDRIVERSFILE, buf, sizeof(buf));
if (r < 0)
return;
char* buf = NULL;
int bufSize = MAX_READ;
int bufLen = 0;
for (;;) {
buf = xRealloc(buf, bufSize);
int size = xread(fd, buf + bufLen, MAX_READ);
if (size <= 0) {
buf[bufLen] = '\0';
close(fd);
break;
}
bufLen += size;
bufSize += MAX_READ;
}
if (bufLen == 0) {
free(buf);
return;
}
int numDrivers = 0;
int allocd = 10;
ttyDrivers = xMalloc(sizeof(TtyDriver) * allocd);
@ -169,7 +130,6 @@ static void LinuxProcessList_initTtyDrivers(LinuxProcessList* this) {
ttyDrivers = xRealloc(ttyDrivers, sizeof(TtyDriver) * allocd);
}
}
free(buf);
numDrivers++;
ttyDrivers = xRealloc(ttyDrivers, sizeof(TtyDriver) * numDrivers);
ttyDrivers[numDrivers - 1].path = NULL;
@ -325,17 +285,11 @@ static bool LinuxProcessList_readStatFile(Process* process, openat_arg_t procFd,
LinuxProcess* lp = (LinuxProcess*) process;
const int commLenIn = *commLen;
*commLen = 0;
int fd = Compat_openat(procFd, "stat", O_RDONLY);
if (fd == -1)
return false;
static char buf[MAX_READ + 1];
int size = xread(fd, buf, MAX_READ);
close(fd);
if (size <= 0)
char buf[MAX_READ + 1];
ssize_t r = xReadfileat(procFd, "stat", buf, sizeof(buf));
if (r < 0)
return false;
buf[size] = '\0';
assert(process->pid == atoi(buf));
char* location = strchr(buf, ' ');
@ -425,8 +379,9 @@ static bool LinuxProcessList_statProcessDir(Process* process, openat_arg_t procF
}
static void LinuxProcessList_readIoFile(LinuxProcess* process, openat_arg_t procFd, unsigned long long now) {
int fd = Compat_openat(procFd, "io", O_RDONLY);
if (fd == -1) {
char buffer[1024];
ssize_t r = xReadfileat(procFd, "io", buffer, sizeof(buffer));
if (r < 0) {
process->io_rate_read_bps = NAN;
process->io_rate_write_bps = NAN;
process->io_rchar = -1LL;
@ -441,13 +396,6 @@ static void LinuxProcessList_readIoFile(LinuxProcess* process, openat_arg_t proc
return;
}
char buffer[1024];
ssize_t buflen = xread(fd, buffer, 1023);
close(fd);
if (buflen < 1)
return;
buffer[buflen] = '\0';
unsigned long long last_read = process->io_read_bytes;
unsigned long long last_write = process->io_write_bytes;
char* buf = buffer;
@ -1015,14 +963,10 @@ static void setCommand(Process* process, const char* command, int len) {
}
static bool LinuxProcessList_readCmdlineFile(Process* process, openat_arg_t procFd) {
LinuxProcess *lp = (LinuxProcess *)process;
int fd = Compat_openat(procFd, "cmdline", O_RDONLY);
if (fd == -1)
return false;
char command[4096 + 1]; // max cmdline length on Linux
int amtRead = xread(fd, command, sizeof(command) - 1);
close(fd);
ssize_t amtRead = xReadfileat(procFd, "cmdline", command, sizeof(command));
if (amtRead < 0)
return false;
if (amtRead == 0) {
if (process->state == 'Z') {
@ -1031,8 +975,6 @@ static bool LinuxProcessList_readCmdlineFile(Process* process, openat_arg_t proc
((LinuxProcess*)process)->isKernelThread = true;
}
return true;
} else if (amtRead < 0) {
return false;
}
int tokenEnd = 0;
@ -1145,6 +1087,7 @@ static bool LinuxProcessList_readCmdlineFile(Process* process, openat_arg_t proc
tokenEnd = lastChar + 1;
}
LinuxProcess *lp = (LinuxProcess *)process;
lp->mergedCommand.maxLen = lastChar + 1; /* accommodate cmdline */
if (!process->comm || !String_eq(command, process->comm)) {
process->basenameOffset = tokenEnd;
@ -1155,9 +1098,8 @@ static bool LinuxProcessList_readCmdlineFile(Process* process, openat_arg_t proc
}
/* /proc/[pid]/comm could change, so should be updated */
if ((fd = Compat_openat(procFd, "comm", O_RDONLY)) != -1 &&
(amtRead = xread(fd, command, sizeof(command) - 1)) > 0) {
command[amtRead - 1] = 0;
if ((amtRead = xReadfileat(procFd, "comm", command, sizeof(command))) > 0) {
command[amtRead - 1] = '\0';
lp->mergedCommand.maxLen += amtRead - 1; /* accommodate comm */
if (!lp->procComm || !String_eq(command, lp->procComm)) {
free(lp->procComm);
@ -1170,9 +1112,6 @@ static bool LinuxProcessList_readCmdlineFile(Process* process, openat_arg_t proc
lp->mergedCommand.commChanged = true;
}
if (fd != -1)
close(fd);
char filename[MAX_NAME + 1];
/* execve could change /proc/[pid]/exe, so procExe should be updated */