Allow partial dup_stdout_on_close, add comments

core/lib/globals_shared.h

@@ -120,12 +120,14 @@
 # define X86_64
 #endif
 
-/* DR_API EXPORT VERBATIM */
 #include <limits.h>  /* for USHRT_MAX */
 #ifdef UNIX
-#  include <sys/types.h>        /* Fix for case 5341. */
 #  include <signal.h>
 #endif
+/* DR_API EXPORT VERBATIM */
+#ifdef UNIX
+#  include <sys/types.h>  /* Fix for case 5341. And for pid_t (non-glibc) */
+#endif
 #ifdef WINDOWS
 /* allow nameless struct/union */
 #  pragma warning(disable: 4201)

core/unix/injector.c

@@ -153,6 +153,7 @@ typedef struct _dr_inject_info_t {
 static bool
 inject_ptrace(dr_inject_info_t *info, const char *library_path);
 
+/* "enum __ptrace_request request" is used by glibc, but musl uses "int". */
 static long
 our_ptrace(int request, pid_t pid, void *addr, void *data);
 #endif

core/unix/os.c

@@ -6168,6 +6168,22 @@ cleanup_after_vfork_execve(dcontext_t *dcontext)
                      HEAPACCT(ACCT_THREAD_MGT));
 }
 
+static void
+set_stdfile_fileno(stdfile_t **stdfile, file_t file_no) {
+#ifdef STDFILE_FILENO
+  (*stdfile)->STDFILE_FILENO = file_no;
+#else
+  /* this occurs on musl libc */
+  #warning stdfile_t is opaque; DynamoRIO will skip setting fds of libc FILEs.
+  /* only called by handle_close_pre(), so this warning is specific to that. */
+  SYSLOG_INTERNAL_WARNING_ONCE(
+    "DynamoRIO cannot set the file descriptors of private libc FILEs on this "
+    "platform. Client usage of stdio.h stdin, stdout, or stderr may no longer "
+    "work as expected, because the app is closing the UNIX fds backing these."
+  );
+#endif
+}
+
 /* returns whether to execute syscall */
 static bool
 handle_close_pre(dcontext_t *dcontext)
@@ -6191,7 +6207,6 @@ handle_close_pre(dcontext_t *dcontext)
 
     /* Xref PR 258731 - duplicate STDOUT/STDERR when app closes them so we (or
      * a client) can continue to use them for logging. */
-#ifdef STDFILE_FILENO
     if (DYNAMO_OPTION(dup_stdout_on_close) && fd == STDOUT) {
         our_stdout = fd_priv_dup(fd);
         if (our_stdout < 0) /* no private fd available */
@@ -6205,7 +6220,7 @@ handle_close_pre(dcontext_t *dcontext)
         if (privmod_stdout != NULL &&
             IF_CLIENT_INTERFACE_ELSE(INTERNAL_OPTION(private_loader), false)) {
             /* update the privately loaded libc's stdout _fileno. */
-            (*privmod_stdout)->STDFILE_FILENO = our_stdout;
+            set_stdfile_fileno(privmod_stdout, our_stdout);
         }
     }
     if (DYNAMO_OPTION(dup_stderr_on_close) && fd == STDERR) {
@@ -6221,7 +6236,7 @@ handle_close_pre(dcontext_t *dcontext)
         if (privmod_stderr != NULL &&
             IF_CLIENT_INTERFACE_ELSE(INTERNAL_OPTION(private_loader), false)) {
             /* update the privately loaded libc's stderr _fileno. */
-            (*privmod_stderr)->STDFILE_FILENO = our_stderr;
+            set_stdfile_fileno(privmod_stderr, our_stderr);
         }
     }
     if (DYNAMO_OPTION(dup_stdin_on_close) && fd == STDIN) {
@@ -6237,10 +6252,9 @@ handle_close_pre(dcontext_t *dcontext)
         if (privmod_stdin != NULL &&
             IF_CLIENT_INTERFACE_ELSE(INTERNAL_OPTION(private_loader), false)) {
             /* update the privately loaded libc's stdout _fileno. */
-            (*privmod_stdin)->STDFILE_FILENO = our_stdin;
+            set_stdfile_fileno(privmod_stdin, our_stdin);
         }
     }
-#endif
     return true;
 }
 

core/unix/signal_private.h

@@ -534,6 +534,9 @@ libc_sigismember(const sigset_t *set, int _sig)
     /* sigset_t is just a uint32 */
     return TEST(1UL << sig, *set);
 #else
+    /* "set->__val" would be cleaner, but is glibc specific (e.g. musl libc
+     * uses __bits as the field name on sigset_t).
+     */
     uint bits_per = 8*sizeof(ulong);
     return TEST(1UL << (sig % bits_per), ((const ulong *)set)[sig / bits_per]);
 #endif