0.18.1 --- SIGHUP is a request to end, and a #! script is given its name (#40)

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>

Author: Sunrisepeak

README.md

@@ -8,7 +8,7 @@ for Linux, written on the kernel's own system-call interface.
 openkal = "0.17.0"
 
 [target.'cfg(os = "linux")'.dependencies]
-openkal-linux = "0.18.0"
+openkal-linux = "0.18.1"
 ```
 
 ## Why it does not use a C library

mcpp.toml

@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-linux"
-version     = "0.18.0"
+version     = "0.18.1"
 description = "The reference implementation of openkal for Linux, written on the kernel's own system-call interface so that it can be placed beneath a C library as well as above one."
 license     = "Apache-2.0"
 
@@ -63,7 +63,7 @@ provides-interfaces = [
 ]
 
 [dependencies]
-openkal = "0.17.0"
+openkal = "0.17.1"
 
 # The package contributes definitions and no modules. The interface it
 # implements is declared by the specification package, which this package

src/process.cpp

@@ -415,6 +415,16 @@ bool absolute_under(int fd, const char* name, okl_uptr len, char* out, okl_uptr
     return true;
 }
 
+// Whether `name' reaches the file `fd' holds: the same device and inode.
+bool same_file(okl_long fd, const char* name) {
+    okl::kstat held{}, named{};
+    if (okl::failed(okl::sys(okl::nr_fstat, fd, reinterpret_cast<okl_long>(&held)))) return false;
+    if (okl::failed(okl::sys(okl::nr_newfstatat, okl::at_fdcwd, reinterpret_cast<okl_long>(name),
+                             reinterpret_cast<okl_long>(&named), 0)))
+        return false;
+    return held.dev == named.dev && held.ino == named.ino;
+}
+
 }  // namespace
 
 // EVERY ENVIRONMENT ENTRY IS `NAME=value' (0.17, process.h). Refused before
@@ -643,11 +653,18 @@ int kal_process_spawn(const kal_spawn* how,
         // the caller had no standard input and supplied none, the lowest free
         // number is 0, and a script would read its own descriptor as input.
         //
-        // What is given up: a script now sees `$0' as `/dev/fd/<n>' and not as
-        // a path under its directory, so one that locates its neighbours with
-        // `dirname "$0"' no longer finds them. That is the price of leaving a
-        // descriptor for the file and not for the directory, the same one
-        // `fexecve' charges. The descriptor still names the program: it can be
+        // A SCRIPT IS GIVEN ITS NAME WHERE THE NAME REACHES THE SAME FILE
+        // (0.18.1). Through the descriptor a script sees `$0' as `/dev/fd/<n>',
+        // and one that locates its neighbours with `dirname "$0"' --- a wrapper
+        // installed beside the files it runs, a test's stub provider --- finds
+        // none of them: measured in mcpp, whose provider stub wrote beside
+        // itself into `/dev/fd/ticks'. So a program that needs an interpreter is
+        // started by its absolute name, as every shell and `posix_spawn' start
+        // it, when that name is known and names the file the descriptor holds
+        // (the same device and inode, so the name grants nothing the descriptor
+        // did not). Only where it does not --- a base the kernel cannot name, a
+        // name rebound since it was opened --- is the descriptor kept, with the
+        // price stated above: the descriptor still names the program and can be
         // reopened through `/proc/self/fd/<n>', as `/proc/self/exe' can.
         //
         // Opened HERE, in the started image, and not where the preopens are made:
@@ -679,6 +696,10 @@ int kal_process_spawn(const kal_spawn* how,
                             reinterpret_cast<okl_long>(envs.slots), okl::at_empty_path);
         };
         okl_long why = start();
+        if (why == -okl::e_noent && named && same_file(exe, resolved))
+            why = okl::sys(okl::nr_execve, reinterpret_cast<okl_long>(resolved),
+                           reinterpret_cast<okl_long>(args.slots),
+                           reinterpret_cast<okl_long>(envs.slots));
         if (why == -okl::e_noent) {
             okl::sys(okl::nr_fcntl, exe, okl::f_setfd, 0);
             why = start();
@@ -951,7 +972,11 @@ const kal_u32* kal_process_stop_requested(void) {
     // caller is told what the first found rather than arming again.
     int state = __atomic_load_n(&g_stop_armed, __ATOMIC_ACQUIRE);
     if (state == 0) {
-        const bool ok = arm_one(15) && arm_one(2);   // SIGTERM, SIGINT
+        // SIGTERM, SIGINT and SIGHUP (0.18.1): the terminal that started a
+        // program closing is a request to end it as much as the other two, and
+        // a program that took the requests over and not this one was ended by
+        // it before it could finish in order.
+        const bool ok = arm_one(15) && arm_one(2) && arm_one(1);
         state = ok ? 1 : -1;
         __atomic_store_n(&g_stop_armed, state, __ATOMIC_RELEASE);
     }

tests/script_sees_its_name.cpp

@@ -0,0 +1,71 @@
+// A `#!' script is given its name (0.18.1).
+//
+// Started through the descriptor, a script saw `$0' as `/dev/fd/<n>', and one
+// that locates its neighbours with `dirname "$0"' found none of them. A
+// program that needs an interpreter is now started by its absolute name where
+// that name reaches the file the descriptor holds.
+//
+// The script writes beside itself, under the name its `$0' gives; the test
+// reads the file back from the directory it placed the script in.
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+import openkal.types;
+import openkal.fs;
+import openkal.process;
+
+namespace {
+kal_dir root() {
+    for (kal_uintptr i = 0; i < kal_fs_preopen_count(); ++i) {
+        kal_dir d{}; char n[8]; kal_uintptr l = 0;
+        if (kal_fs_preopen(i, &d, n, sizeof n, &l) == kal_ok && l == 1 && n[0] == '/') return d;
+    }
+    return kal_dir{};
+}
+}
+
+int main() {
+    char dir[] = "/tmp/okl-script-XXXXXX";
+    if (::mkdtemp(dir) == nullptr) { std::printf("FAIL: a scratch directory\n"); return 1; }
+    char script[256], beside[256];
+    std::snprintf(script, sizeof script, "%s/stub", dir);
+    std::snprintf(beside, sizeof beside, "%s/beside", dir);
+    {
+        const int fd = ::open(script, O_WRONLY | O_CREAT | O_TRUNC, 0755);
+        const char text[] = "#!/bin/sh\nprintf '%s' \"$0\" > \"${0%/*}/beside\"\n";
+        const bool written = fd >= 0 && ::write(fd, text, sizeof text - 1) == static_cast<ssize_t>(sizeof text - 1);
+        if (fd >= 0) ::close(fd);
+        if (!written) { std::printf("FAIL: the script is written\n"); return 1; }
+    }
+
+    const kal_dir r = root();
+    const char* argv[] = { script };
+    const kal_uintptr lens[] = { std::strlen(script) };
+    const kal_spawn how{ r, r, nullptr, nullptr, 0, 0 };
+    kal_process p{};
+    const int e = kal_process_spawn(&how, script + 1, std::strlen(script + 1), argv, lens, 1,
+                                    nullptr, nullptr, 0, nullptr, &p);
+    int status = -1, terminated = 0;
+    if (e == kal_ok) kal_process_wait(p, &status, &terminated);
+
+    char seen[256] = {};
+    if (FILE* f = std::fopen(beside, "r")) { std::fgets(seen, sizeof seen, f); std::fclose(f); }
+    ::unlink(beside);
+    ::unlink(script);
+    ::rmdir(dir);
+
+    int failures = 0;
+    if (e != kal_ok || terminated != 0 || status != 0) {
+        std::printf("FAIL: the script is started (rc %d, status %d)\n", e, status);
+        ++failures;
+    }
+    if (std::strcmp(seen, script) != 0) {
+        std::printf("FAIL: the script sees its own name as $0 (saw '%s')\n", seen);
+        ++failures;
+    }
+    if (failures == 0) std::printf("openkal-linux: a script is given its name\n");
+    return failures == 0 ? 0 : 1;
+}

tests/stop_word_take_over.cpp

@@ -25,6 +25,17 @@ void check(bool held, const char* what) {
 }
 
 int main(int argc, char** argv) {
+    if (argc > 1 && std::strcmp(argv[1], "--hang-up") == 0) {
+        // 0.18.1: the closing of the terminal is a request to end, taken over
+        // with the others, and the program ends as it would have.
+        const kal_u32* word = kal_process_stop_requested();
+        if (word == nullptr) return 90;
+        ::kill(::getpid(), SIGHUP);
+        for (int i = 0; i < 1000 && *word == 0; ++i) ::usleep(1000);
+        if (*word == 0) return 91;
+        kal_process_end_as_requested();
+        return 92;
+    }
     if (argc > 1 && std::strcmp(argv[1], "--end-as-requested") == 0) {
         const kal_u32* word = kal_process_stop_requested();
         if (word == nullptr) return 90;
@@ -58,6 +69,16 @@ int main(int argc, char** argv) {
     check(WIFSIGNALED(st) && WTERMSIG(st) == SIGTERM,
           "a program that ends as requested is reported to its starter as ended by the request");
 
+    const pid_t hung = ::fork();
+    if (hung == 0) {
+        ::execl("/proc/self/exe", argv[0], "--hang-up", nullptr);
+        ::_exit(93);
+    }
+    st = 0;
+    ::waitpid(hung, &st, 0);
+    check(WIFSIGNALED(st) && WTERMSIG(st) == SIGHUP,
+          "a hang-up is taken over as a request, and the program ends as it would have");
+
     if (failures == 0) std::printf("openkal-linux: the stop word is taken over and given back\n");
     return failures == 0 ? 0 : 1;
 }