i#1973 musl libc: Build on musl libc systems (#2916)

These changes seem sufficient to allow building dynamorio on an alpine linux container, and to successfully run some basic clients.  No further testing was done.  While this can successfully build against musl, there are probably some things broken at runtime.

Issue: #1973

core/lib/globals_shared.h

@@ -122,10 +122,12 @@
 
 #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>  /* for pid_t (non-glibc, e.g. musl) */
+#endif
 #ifdef WINDOWS
 /* allow nameless struct/union */
 #  pragma warning(disable: 4201)

core/unix/injector.c

@@ -153,8 +153,9 @@ 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(enum __ptrace_request request, pid_t pid, void *addr, void *data);
+our_ptrace(int request, pid_t pid, void *addr, void *data);
 #endif
 
 /*******************************************************************************
@@ -889,7 +890,7 @@ static const enum_name_pair_t pt_req_map[] = {
  * libc from the injector process should always work.
  */
 static long
-our_ptrace(enum __ptrace_request request, pid_t pid, void *addr, void *data)
+our_ptrace(int request, pid_t pid, void *addr, void *data)
 {
     long r = dynamorio_syscall(SYS_ptrace, 4, request, pid, addr, data);
     if (verbose &&

core/unix/module.h

@@ -185,7 +185,9 @@ typedef FILE stdfile_t;
 # define STDFILE_FILENO _file
 #elif defined(LINUX)
 typedef struct _IO_FILE stdfile_t;
-# define STDFILE_FILENO _fileno
+# ifdef __GLIBC__
+#  define STDFILE_FILENO _fileno
+# endif
 #endif
 extern stdfile_t **privmod_stdout;
 extern stdfile_t **privmod_stderr;

core/unix/os.c

@@ -6168,6 +6168,23 @@ 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
+# warning stdfile_t is opaque; DynamoRIO will not set fds of libc FILEs.
+    /* i#1973: musl libc support (and potentially other non-glibcs) */
+    /* only called by handle_close_pre(), so 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)
@@ -6204,7 +6221,7 @@ 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) {
@@ -6220,7 +6237,7 @@ 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) {
@@ -6236,7 +6253,7 @@ 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);
         }
     }
     return true;

core/unix/signal.c

@@ -96,9 +96,11 @@
 # include <errno.h>
 #endif
 
-#ifdef MACOS
 /* Define the Linux names, which the code is already using */
+#ifndef SA_NOMASK
 #  define SA_NOMASK       SA_NODEFER
+#endif
+#ifndef SA_ONESHOT
 #  define SA_ONESHOT      SA_RESETHAND
 #endif
 

core/unix/signal_linux.c

@@ -475,7 +475,7 @@ notify_signalfd(dcontext_t *dcontext, thread_sig_info_t *info, int sig,
 #ifdef ANDROID
         towrite.ssi_tid = frame->info._sifields._timer._tid;
 #else
-        towrite.ssi_tid = frame->info._sifields._timer.si_tid;
+        towrite.ssi_tid = frame->info.si_timerid;
 #endif
         towrite.ssi_overrun = frame->info.si_overrun;
         towrite.ssi_status = frame->info.si_status;

core/unix/signal_private.h

@@ -534,8 +534,11 @@ 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), set->__val[sig / bits_per]);
+    return TEST(1UL << (sig % bits_per), ((const ulong *)set)[sig / bits_per]);
 #endif
 }