hush: make read builtin interruptible.

function                                             old     new   delta
builtin_read                                         185     471    +286
check_and_run_traps                                  200     262     +62
nonblock_immune_read                                  73     119     +46
sigismember                                            -      44     +44
record_signal                                          -      21     +21
sigisemptyset                                          -      16     +16
...
------------------------------------------------------------------------------
(add/remove: 5/0 grow/shrink: 7/5 up/down: 483/-46)           Total: 437 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/shell/shell_common.c b/shell/shell_common.c
index 86a6493ed..a5c455c8e 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -36,6 +36,10 @@ int FAST_FUNC is_well_formed_var_name(const char *s, char terminator)
 
 /* read builtin */
 
+/* Needs to be interruptible: shell mush handle traps and shell-special signals
+ * while inside read. To implement this, be sure to not loop on EINTR
+ * and return errno == EINTR reliably.
+ */
 //TODO: use more efficient setvar() which takes a pointer to malloced "VAR=VAL"
 //string. hush naturally has it, and ash has setvareq().
 //Here we can simply store "VAR=" at buffer start and store read data directly
@@ -51,6 +55,7 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
         const char *opt_u
 )
 {
+        unsigned err;
         unsigned end_ms; /* -t TIMEOUT */
         int fd; /* -u FD */
         int nchars; /* -n NUM */
@@ -62,6 +67,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
         int startword;
         smallint backslash;
 
+        errno = err = 0;
+
         pp = argv;
         while (*pp) {
                 if (!is_well_formed_var_name(*pp, '\0')) {
@@ -153,6 +160,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
         do {
                 char c;
 
+                errno = 0;
+
                 if (end_ms) {
                         int timeout;
                         struct pollfd pfd[1];
@@ -161,8 +170,9 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
                         pfd[0].events = POLLIN;
                         timeout = end_ms - (unsigned)monotonic_ms();
                         if (timeout <= 0 /* already late? */
-                         || safe_poll(pfd, 1, timeout) != 1 /* no? wait... */
+                         || poll(pfd, 1, timeout) != 1 /* no? wait... */
                         ) { /* timed out! */
+                                err = errno;
                                 retval = (const char *)(uintptr_t)1;
                                 goto ret;
                         }
@@ -170,7 +180,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
 
                 if ((bufpos & 0xff) == 0)
                         buffer = xrealloc(buffer, bufpos + 0x100);
-                if (nonblock_immune_read(fd, &buffer[bufpos], 1) != 1) {
+                if (nonblock_immune_read(fd, &buffer[bufpos], 1, /*loop_on_EINTR:*/ 0) != 1) {
+                        err = errno;
                         retval = (const char *)(uintptr_t)1;
                         break;
                 }
@@ -240,6 +251,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
         free(buffer);
         if (read_flags & BUILTIN_READ_SILENT)
                 tcsetattr(fd, TCSANOW, &old_tty);
+
+        errno = err;
         return retval;
 }