From 9bb1720cca710e5954d7084f4a74c8e930aaa156 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Fri, 7 Apr 2023 15:39:10 +0200
Subject: [PATCH] libc: Add execvp() and execvpe()

---
 apps/sh.cpp           | 46 +------------------------------------------
 libc/include/unistd.h |  6 +++++-
 libc/src/unistd.cpp   | 43 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 46 deletions(-)

diff --git a/apps/sh.cpp b/apps/sh.cpp
index 7a8d1a45..2695d33e 100644
--- a/apps/sh.cpp
+++ b/apps/sh.cpp
@@ -31,50 +31,6 @@ static Result<Vector<char*>> split_command_into_argv(const char* cmd)
     return result;
 }
 
-static Result<String> join_path(const char* str1, const char* str2)
-{
-    StringBuilder sb;
-    TRY(sb.add(StringView { str1 }));
-    TRY(sb.add(StringView { str2 }));
-    return sb.string();
-}
-
-static int execute_in_path(const char* dir, char** argv)
-{
-    String path;
-    bool ok = join_path(dir, argv[0]).try_move_value_or_error(path, errno);
-    if (!ok) return -1;
-
-    int err = errno;
-
-    int status = execv(path.chars(), argv);
-
-    if (errno == ENOENT)
-    {
-        errno = err;
-        return 0;
-    }
-
-    return status;
-}
-
-static int sh_execvp(char** argv)
-{
-    if (strchr(argv[0], '/'))
-    {
-        // Relative paths do not need path resolution.
-        return execv(argv[0], argv);
-    }
-
-    if (execute_in_path("/bin/", argv) != 0) return -1;
-    if (execute_in_path("/sbin/", argv) != 0) return -1;
-    if (execute_in_path("/usr/bin/", argv) != 0) return -1;
-    if (execute_in_path("/usr/local/bin/", argv) != 0) return -1;
-
-    errno = ENOENT;
-    return -1;
-}
-
 int main()
 {
     while (1)
@@ -105,7 +61,7 @@ int main()
             }
 
             if (argv[0] == NULL) return 0;
-            sh_execvp(argv.data());
+            execvp(argv[0], argv.data());
             perror(argv[0]);
             return 1;
         }
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 859ba4bb..ca851079 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -37,7 +37,11 @@ extern "C"
     /* Replace the current process with another one. On success, does not return. */
     int execve(const char* path, char* const* argv, char* const* envp);
 
-    int execvp(const char*, char* const*);
+    /* Replace the current process with another one. On success, does not return. */
+    int execvp(const char* name, char* const* argv);
+
+    /* Replace the current process with another one. On success, does not return. */
+    int execvpe(const char* name, char* const* argv, char* const* envp);
 
     /* Call the operating system kernel for a specific service. */
     long syscall(long num, ...);
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index 423bf17b..fba619e9 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -1,9 +1,11 @@
+#include <luna/StringBuilder.h>
 #include <luna/Vector.h>
 
 #include <bits/errno-return.h>
 #include <fcntl.h>
 #include <stdarg.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
@@ -40,6 +42,47 @@ extern "C"
         __errno_return(rc, int);
     }
 
+    int execvpe(const char* name, char* const* argv, char* const* envp)
+    {
+        if (strchr(name, '/')) return execve(name, argv, envp);
+
+        char* path = getenv("PATH");
+        if (!path) path = const_cast<char*>("/bin:/sbin");
+
+        Vector<String> paths;
+        bool ok = StringView { path }.split(":").try_move_value_or_error(paths, errno);
+        if (!ok) return -1;
+
+        for (const auto& dir : paths)
+        {
+            // FIXME: Check for errors.
+            StringBuilder sb;
+            sb.add(dir);
+            sb.add('/');
+            sb.add(StringView { name });
+
+            String file;
+            ok = sb.string().try_move_value_or_error(file, errno);
+            if (!ok) return -1;
+
+            int err = errno;
+            execve(file.chars(), argv, envp);
+
+            if (errno != ENOENT && errno != EACCES) return -1;
+
+            // FIXME: POSIX says that if errno == ENOEXEC, we should run /bin/sh <path>.
+
+            if (err == EACCES) errno = err;
+        }
+
+        return -1;
+    }
+
+    int execvp(const char* name, char* const* argv)
+    {
+        return execvpe(name, argv, environ);
+    }
+
     int execl(const char* path, const char* arg, ...)
     {
         va_list ap;