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Fix the unixfork/unixcomm code to deal with pid over 65535 (#333)

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* ForkUnixShell() can be a static procedure

* Restructure SAFEREAD() to be a little clearer

* Convert unixjob type field defines to an enum and fix related unhandled switch cases.

* Use local declaration of loop variables in for-loop, removing register attributes

* Restructure SAFEREAD() to be a little clearer

* Send and receive 2 additional bytes for pid.

* Prefer standard C99 "inline" over "__inline__" for SAFEREAD
This commit is contained in:
Nick Briggs
2021-02-08 18:26:56 -08:00
committed by GitHub
parent d482cc461c
commit 2aacca596b
3 changed files with 84 additions and 75 deletions
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60
src/unixfork.c
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@@ -54,16 +54,14 @@ char shcom[512]; /* Here because I'm suspicious of */
/* large allocations on the stack */
static __inline__ ssize_t
SAFEREAD(int f, char *b, int c)
static inline ssize_t SAFEREAD(int f, char *b, int c)
{
ssize_t res;
loop:
res = read(f, b, c);
if ((res < 0)) {
if (errno == EINTR || errno == EAGAIN) goto loop;
perror("reading UnixPipeIn");
}
do {
res = read(f, b, c);
if (res >= 0) return (res);
} while (errno == EINTR || errno == EAGAIN);
perror("reading UnixPipeIn");
return (res);
}
@@ -79,7 +77,7 @@ loop:
/* Creates a PTY connection to a csh */
int ForkUnixShell(int slot, char *PtySlave, char *termtype, char *shellarg)
static int ForkUnixShell(int slot, char *PtySlave, char *termtype, char *shellarg)
{
int PID, SlaveFD;
struct termios tio;
@@ -152,7 +150,7 @@ int ForkUnixShell(int slot, char *PtySlave, char *termtype, char *shellarg)
/* fork_Unix is the secondary process spawned right after LISP is
started, to avoid having TWO 8 mbyte images sitting around. It listens
to the pipe LispToUnix waiting for requests, and responds on UnixToLisp.
The data passed through this pipe is in 4 byte packets, of the form:
The data passed through this pipe is in 6 byte packets, of the form:
Byte 0: Command character, one of:
S: Fork PTY (shell) process. This is used for CHAT windows.
@@ -169,26 +167,26 @@ int ForkUnixShell(int slot, char *PtySlave, char *termtype, char *shellarg)
Only used for W command, contains byte to write
[For S&P, pty number]
Byte 3: Slot number.
Byte 4: unused.
Byte 5: unused.
In the case of F & P commands, additional data follows the 4 byte packet.
In the case of F & P commands, additional data follows the 6 byte packet.
This consists of 2 bytes representing the length of the shell command
string, and the string itself.
fork_Unix will return another 4 byte packet. The bytes are the same as those
fork_Unix will return another 6 byte packet. The bytes are the same as those
of the packet received except:
F: Byte 2 is job number
Byte 3 is 1 if successful, 0 if not
S: Byte 2 is job number
F, S, P: Bytes 1, 2, 4, and 5 are the Unix process id
Byte 3 is 1 if successful, 0 if not
R: Byte 2 is value of byte read from stdin, if any
Byte 3 is 1 if successful, 2 if EOF, 0 if nothing waiting
W: Bytes 0 & 1 are the Process ID of the terminated process
W: Bytes 0, 1, 4, 5 are the Process ID of the terminated process
Bytes 2 & 3 are the high & low bytes of the exit status.
K: Bytes 1 and 2 are the high and low bytes of the exit status
of the process.
Byte 3 is 1 if an exit status was available.
E: Always the same
C: Always the same
*/
@@ -199,7 +197,7 @@ int fork_Unix() {
pid_t pid;
sigset_t signals;
char IOBuf[4];
char IOBuf[6]; /* XXX: signed, because slot comes from here */
unsigned short tmp = 0;
char *cmdstring;
@@ -263,17 +261,13 @@ int fork_Unix() {
while (1) {
ssize_t len;
len = 0;
while (len != 4) {
if ((len = SAFEREAD(LispPipeIn, IOBuf, 4)) < 0) { /* Get packet */
perror("Packet read by slave");
/* kill_comm_processes(); */
exit(0);
}
if (len != 4) {
DBPRINT(("Input packet wrong length: %d.\n", len));
exit(0);
}
len = SAFEREAD(LispPipeIn, IOBuf, 6);
if (len < 0) {
perror("Error reading packet by slave");
exit(0);
} else if (len != 6) {
DBPRINT(("Input packet wrong length: %d", len));
exit(0);
}
slot = IOBuf[3];
IOBuf[3] = 1; /* Start by signalling success in return-code */
@@ -318,6 +312,8 @@ int fork_Unix() {
/* ForkUnixShell sets the pid and standard in/out variables */
IOBuf[1] = (pid >> 8) & 0xFF;
IOBuf[2] = pid & 0xFF;
IOBuf[4] = (pid >> 16) & 0xFF;
IOBuf[5] = (pid >> 24) & 0xFF;
}
} else {
printf("Can't get process slot for PTY shell.\n");
@@ -388,6 +384,8 @@ int fork_Unix() {
} else {
IOBuf[1] = (pid >> 8) & 0xFF;
IOBuf[2] = pid & 0xFF;
IOBuf[4] = (pid >> 16) & 0xFF;
IOBuf[5] = (pid >> 24) & 0xFF;
}
} else {
printf("No process slots available.\n");
@@ -411,6 +409,8 @@ int fork_Unix() {
/* Ignore processes which are suspended but haven't exited
(this shouldn't happen) */
if (WIFSTOPPED(status)) break;
IOBuf[5] = (pid >> 24) & 0xFF;
IOBuf[4] = (pid >> 16) & 0xFF;
IOBuf[3] = status >> 8;
IOBuf[2] = status & 0xFF;
IOBuf[1] = pid & 0xFF;
@@ -427,7 +427,7 @@ int fork_Unix() {
} /* End of switch */
/* Return the status/data packet */
write(LispPipeOut, IOBuf, 4);
write(LispPipeOut, IOBuf, 6);
}
}