linux: Add PR_SET_VMA_ANON_NAME support

Linux 5.17 added support to naming anonymous virtual memory areas
through the prctl syscall.  The __set_vma_name is a wrapper to avoid
optimizing the prctl call if the kernel does not support it.

If the kernel does not support PR_SET_VMA_ANON_NAME, prctl returns
EINVAL. And it also returns the same error for an invalid argument.
Since it is an internal-only API, it assumes well-formatted input:
aligned START, with (START, START+LEN) being a valid memory range,
and NAME with a limit of 80 characters without an invalid one
("\\`$[]").
Reviewed-by: DJ Delorie <dj@redhat.com>

3 files changed, 81 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 063719bae6..250df6f455 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -97,6 +97,7 @@ sysdep_routines += \
   readahead \
   setfsgid \
   setfsuid \
+  setvmaname \
   signalfd \
   splice \
   sysctl \
diff --git a/sysdeps/unix/sysv/linux/setvmaname.c b/sysdeps/unix/sysv/linux/setvmaname.c
new file mode 100644
index 0000000000..9960ab5917
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/setvmaname.c
@@ -0,0 +1,44 @@
+/* Utilities functions to name memory mappings.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+#include <setvmaname.h>
+#include <sys/prctl.h>
+#include <sysdep.h>
+
+/* If PR_SET_VMA_ANON_NAME is not supported by the kernel, prctl returns
+   EINVAL.  However, it also returns the same error for invalid argument.
+   Since it is an internal-only API, it assumes well formatted input:
+   aligned START, with (START, START+LEN) being a valid memory range,
+   and NAME with a limit of 80 characters without invalid one ("\\`$[]").  */
+
+void
+__set_vma_name (void *start, size_t len, const char *name)
+{
+  static int prctl_supported = 1;
+  if (atomic_load_relaxed (&prctl_supported) == 0)
+    return;
+
+  int r = INTERNAL_SYSCALL_CALL (prctl, PR_SET_VMA, PR_SET_VMA_ANON_NAME,
+				 start, len, name);
+  if (r == 0 || r != -EINVAL)
+    return;
+
+  atomic_store_relaxed (&prctl_supported, 0);
+  return;
+}
diff --git a/sysdeps/unix/sysv/linux/setvmaname.h b/sysdeps/unix/sysv/linux/setvmaname.h
new file mode 100644
index 0000000000..eaa7a7a32e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/setvmaname.h
@@ -0,0 +1,36 @@
+/* Utilities functions to name memory mappings.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef __SETVMANAME_H
+#define __SETVMANAME_H
+
+/* Set the NAME to the anonymous memory map START with size of LEN.
+   It assumes well-formatted input.  */
+#if IS_IN(libc) || IS_IN(rtld)
+void __set_vma_name (void *start, size_t len, const char *name)
+  attribute_hidden;
+#else
+#include <sys/prctl.h>
+
+static inline void __set_vma_name (void *start, size_t len, const char *name)
+{
+  prctl (PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, name);
+}
+#endif
+
+#endif