skalibs

commit f020ee0ec716aca176cbde6686e9a51d93bb65ab
parent 4dcf9fa0521a1c4243c28fb2f657d8029317e55e
Author: ccx <ccx@te2000.cz>
Date:   Fri, 31 May 2024 19:56:36 +0000

Barebones hardcoded implementation of CLONE_NEWPID

Diffstat:
M
src/include/skalibs/cspawn.h
 | 
1
+
M
src/libenvexec/cspawn.c
 | 
69
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 70 insertions(+), 0 deletions(-)
diff --git a/src/include/skalibs/cspawn.h b/src/include/skalibs/cspawn.h
@@ -9,6 +9,7 @@
 #define CSPAWN_FLAGS_SELFPIPE_FINISH 0x0001U
 #define CSPAWN_FLAGS_SIGBLOCKNONE 0x0002U
 #define CSPAWN_FLAGS_SETSID 0x0004U
+#define CSPAWN_FLAGS_LINUX_NEWPID 0x0100U
 
 enum cspawn_fileaction_type_e
 {
diff --git a/src/libenvexec/cspawn.c b/src/libenvexec/cspawn.c
@@ -9,6 +9,11 @@
 #include <errno.h>
 #include <unistd.h>
 
+/* for CSPAWN_FLAGS_LINUX_NEWPID (using clone3 syscall) */
+#include <syscall.h>     /* For calling clone3 syscall (currently not in libc) */
+#include <linux/types.h> /* For vendored definition of struct clone_args */
+#include <sched.h>       /* Definition of CLONE_* constants */
+
 #include <skalibs/allreadwrite.h>
 #include <skalibs/sig.h>
 #include <skalibs/djbunix.h>
@@ -94,6 +99,67 @@ static inline pid_t cspawn_fork (char const *prog, char const *const *argv, char
   return pid ;
 }
 
+static inline pid_t cspawn_newpid_fork(void)
+{
+  struct clone_args {
+    __aligned_u64 flags;
+    __aligned_u64 pidfd;
+    __aligned_u64 child_tid;
+    __aligned_u64 parent_tid;
+    __aligned_u64 exit_signal;
+    __aligned_u64 stack;
+    __aligned_u64 stack_size;
+    __aligned_u64 tls;
+    __aligned_u64 set_tid;
+    __aligned_u64 set_tid_size;
+    __aligned_u64 cgroup;
+  } args = {
+    .flags = CLONE_NEWPID,
+    .exit_signal = SIGCHLD,
+  };
+
+  return syscall(__NR_clone3, &args, sizeof(args));
+}
+
+static inline pid_t cspawn_newpid (char const *prog, char const *const *argv, char const *const *envp, uint16_t flags, cspawn_fileaction const *fa, size_t n)
+{
+  pid_t pid ;
+  int p[2] ;
+  char c ;
+
+  if (pipecoe(p) == -1) return 0 ;
+  pid = cspawn_newpid_fork() ;
+  if (pid == -1)
+  {
+    fd_close(p[1]) ;
+    fd_close(p[0]) ;
+    return 0 ;
+  }
+  if (!pid)
+  {
+    cspawn_child_exec(prog, argv, envp, flags, fa, n) ;
+    c = errno ;
+    fd_write(p[1], &c, 1) ;
+    _exit(127) ;
+  }
+
+  fd_close(p[1]) ;
+  p[1] = fd_read(p[0], &c, 1) ;
+  if (p[1] < 0)
+  {
+    fd_close(p[0]) ;
+    return 0 ;
+  }
+  fd_close(p[0]) ;
+  if (p[1])
+  {
+    wait_pid(pid, &p[0]) ;
+    errno = (unsigned char)c ;
+    return 0 ;
+  }
+  return pid ;
+}
+
  /*
     guess who has a buggy posix_spawn() *and* doesn't have waitid() to work around it?
     if you guessed OpenBSD, you're right!
@@ -271,6 +337,9 @@ pid_t cspawn (char const *prog, char const *const *argv, char const *const *envp
 
 pid_t cspawn (char const *prog, char const *const *argv, char const *const *envp, uint16_t flags, cspawn_fileaction const *fa, size_t n)
 {
+  if (flags & CSPAWN_FLAGS_LINUX_NEWPID)
+    return cspawn_newpid(prog, argv, envp, flags, fa, n) ;
+
 #if !defined(SKALIBS_HASPOSIXSPAWNSETSID) && !defined(SKALIBS_HASPOSIXSPAWNSETSIDNP)
   if (flags & CSPAWN_FLAGS_SETSID) goto dofork ;
 #endif