ld.so: Implement the --list-diagnostics option

NEWS

@@ -14,6 +14,10 @@ Major new features:
   constant on Linux.  MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ)
   and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ).
 
+* The dynamic linker implements the --list-diagnostics option, printing
+  a dump of information related to IFUNC resolver operation and
+  glibc-hwcaps subdirectory selection.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
   [Add deprecations, removals and changes affecting compatibility here]

elf/Makefile

@@ -66,7 +66,7 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
 # interpreter and operating independent of libc.
 rtld-routines	= rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \
   dl-error-minimal dl-conflict dl-hwcaps dl-hwcaps_split dl-hwcaps-subdirs \
-  dl-usage
+  dl-usage dl-diagnostics dl-diagnostics-kernel dl-diagnostics-cpu
 all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
 
 CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables
@@ -677,6 +677,9 @@ CFLAGS-cache.c += $(SYSCONF-FLAGS)
 CFLAGS-rtld.c += $(SYSCONF-FLAGS)
 CFLAGS-dl-usage.c += $(SYSCONF-FLAGS) \
   -D'RTLD="$(rtlddir)/$(rtld-installed-name)"'
+CFLAGS-dl-diagnostics.c += $(SYSCONF-FLAGS) \
+  -D'PREFIX="$(prefix)"' \
+  -D'RTLD="$(rtlddir)/$(rtld-installed-name)"'
 
 cpp-srcs-left := $(all-rtld-routines:=.os)
 lib := rtld

elf/dl-diagnostics-cpu.c

@@ -0,0 +1,24 @@
+/* Print CPU diagnostics data in ld.so.  Stub version.
+   Copyright (C) 2021 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 <dl-diagnostics.h>
+
+void
+_dl_diagnostics_cpu (void)
+{
+}

elf/dl-diagnostics-kernel.c

@@ -0,0 +1,24 @@
+/* Print kernel diagnostics data in ld.so.  Stub version.
+   Copyright (C) 2021 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 <dl-diagnostics.h>
+
+void
+_dl_diagnostics_kernel (void)
+{
+}

elf/dl-diagnostics.c

@@ -0,0 +1,265 @@
+/* Print diagnostics data in ld.so.
+   Copyright (C) 2021 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 <gnu/lib-names.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <unistd.h>
+
+#include <dl-diagnostics.h>
+#include <dl-hwcaps.h>
+#include <dl-main.h>
+#include <dl-procinfo.h>
+#include <dl-sysdep.h>
+#include <ldsodefs.h>
+#include "trusted-dirs.h"
+#include "version.h"
+
+/* Write CH to standard output.  */
+static void
+_dl_putc (char ch)
+{
+  _dl_write (STDOUT_FILENO, &ch, 1);
+}
+
+/* Print CH to standard output, quoting it if necessary.  */
+static void
+print_quoted_char (char ch)
+{
+  if (ch < ' ' || ch > '~')
+    {
+      char buf[4];
+      buf[0] = '\\';
+      buf[1] = '0' + ((ch >> 6) & 7);
+      buf[2] = '0' + ((ch >> 6) & 7);
+      buf[3] = '0' + (ch & 7);
+      _dl_write (STDOUT_FILENO, buf, 4);
+    }
+  else
+    {
+      if (ch == '\\' || ch == '"')
+        _dl_putc ('\\');
+      _dl_putc (ch);
+    }
+}
+
+/* Print S of LEN bytes to standard output, quoting characters as
+   needed.  */
+static void
+print_string_length (const char *s, size_t len)
+{
+  _dl_putc ('"');
+  for (size_t i = 0; i < len; ++i)
+    print_quoted_char (s[i]);
+  _dl_putc ('"');
+}
+
+void
+_dl_diagnostics_print_string (const char *s)
+{
+  if (s == NULL)
+    {
+      _dl_printf ("0x0");
+      return;
+    }
+
+  _dl_putc ('"');
+  while (*s != '\0')
+    {
+      print_quoted_char (*s);
+      ++s;
+    }
+  _dl_putc ('"');
+}
+
+void
+_dl_diagnostics_print_labeled_string (const char *label, const char *s)
+{
+  _dl_printf ("%s=", label);
+  _dl_diagnostics_print_string (s);
+  _dl_putc ('\n');
+}
+
+void
+_dl_diagnostics_print_labeled_value (const char *label, uint64_t value)
+{
+  if (sizeof (value) == sizeof (unsigned long int))
+    /* _dl_printf can print 64-bit values directly.  */
+    _dl_printf ("%s=0x%lx\n", label, (unsigned long int) value);
+  else
+    {
+      uint32_t high = value >> 32;
+      uint32_t low = value;
+      if (high == 0)
+        _dl_printf ("%s=0x%x\n", label, low);
+      else
+        _dl_printf ("%s=0x%x%08x\n", label, high, low);
+    }
+}
+
+/* Return true if ENV is an unfiltered environment variable.  */
+static bool
+unfiltered_envvar (const char *env, size_t *name_length)
+{
+  char *env_equal = strchr (env, '=');
+  if (env_equal == NULL)
+    {
+      /* Always dump malformed entries.  */
+      *name_length = strlen (env);
+      return true;
+    }
+  size_t envname_length = env_equal - env;
+  *name_length = envname_length;
+
+  /* LC_ and LD_ variables.  */
+  if (env[0] == 'L' && (env[1] == 'C' || env[1] == 'D')
+      && env[2] == '_')
+    return true;
+
+  /* MALLOC_ variables.  */
+  if (strncmp (env, "MALLOC_", strlen ("MALLOC_")) == 0)
+    return true;
+
+  static const char unfiltered[] =
+    "DATEMSK\0"
+    "GCONV_PATH\0"
+    "GETCONF_DIR\0"
+    "GETCONF_DIR\0"
+    "GLIBC_TUNABLES\0"
+    "GMON_OUTPUT_PREFIX\0"
+    "HESIOD_CONFIG\0"
+    "HES_DOMAIN\0"
+    "HOSTALIASES\0"
+    "I18NPATH\0"
+    "IFS\0"
+    "LANG\0"
+    "LOCALDOMAIN\0"
+    "LOCPATH\0"
+    "MSGVERB\0"
+    "NIS_DEFAULTS\0"
+    "NIS_GROUP\0"
+    "NIS_PATH\0"
+    "NLSPATH\0"
+    "PATH\0"
+    "POSIXLY_CORRECT\0"
+    "RESOLV_HOST_CONF\0"
+    "RES_OPTIONS\0"
+    "SEV_LEVEL\0"
+    "TMPDIR\0"
+    "TZ\0"
+    "TZDIR\0"
+    /* Two null bytes at the end to mark the end of the list via an
+       empty substring.  */
+    ;
+  for (const char *candidate = unfiltered; *candidate != '\0'; )
+    {
+      size_t candidate_length = strlen (candidate);
+      if (candidate_length == envname_length
+          && memcmp (candidate, env, candidate_length) == 0)
+        return true;
+      candidate += candidate_length + 1;
+    }
+
+  return false;
+}
+
+/* Dump the process environment.  */
+static void
+print_environ (char **environ)
+{
+  unsigned int index = 0;
+  for (char **envp = environ; *envp != NULL; ++envp)
+    {
+      char *env = *envp;
+      size_t name_length;
+      bool unfiltered = unfiltered_envvar (env, &name_length);
+      _dl_printf ("env%s[0x%x]=",
+                  unfiltered ? "" : "_filtered", index);
+      if (unfiltered)
+        _dl_diagnostics_print_string (env);
+      else
+        print_string_length (env, name_length);
+      _dl_putc ('\n');
+      ++index;
+    }
+}
+
+/* Print configured paths and the built-in search path.  */
+static void
+print_paths (void)
+{
+  _dl_diagnostics_print_labeled_string ("path.prefix", PREFIX);
+  _dl_diagnostics_print_labeled_string ("path.rtld", RTLD);
+  _dl_diagnostics_print_labeled_string ("path.sysconfdir", SYSCONFDIR);
+
+  unsigned int index = 0;
+  static const char *system_dirs = SYSTEM_DIRS "\0";
+  for (const char *e = system_dirs; *e != '\0'; )
+    {
+      size_t len = strlen (e);
+      _dl_printf ("path.system_dirs[0x%x]=", index);
+      print_string_length (e, len);
+      _dl_putc ('\n');
+      ++index;
+      e += len + 1;
+    }
+}
+
+/* Print information about the glibc version.  */
+static void
+print_version (void)
+{
+  _dl_diagnostics_print_labeled_string ("version.release", RELEASE);
+  _dl_diagnostics_print_labeled_string ("version.version", VERSION);
+}
+
+void
+_dl_print_diagnostics (char **environ)
+{
+#ifdef HAVE_DL_DISCOVER_OSVERSION
+  _dl_diagnostics_print_labeled_value
+    ("dl_discover_osversion", _dl_discover_osversion ());
+#endif
+  _dl_diagnostics_print_labeled_string ("dl_dst_lib", DL_DST_LIB);
+  _dl_diagnostics_print_labeled_value ("dl_hwcap", GLRO (dl_hwcap));
+  _dl_diagnostics_print_labeled_value ("dl_hwcap_important", HWCAP_IMPORTANT);
+  _dl_diagnostics_print_labeled_value ("dl_hwcap2", GLRO (dl_hwcap2));
+  _dl_diagnostics_print_labeled_string
+    ("dl_hwcaps_subdirs", _dl_hwcaps_subdirs);
+  _dl_diagnostics_print_labeled_value
+    ("dl_hwcaps_subdirs_active", _dl_hwcaps_subdirs_active ());
+  _dl_diagnostics_print_labeled_value ("dl_osversion", GLRO (dl_osversion));
+  _dl_diagnostics_print_labeled_value ("dl_pagesize", GLRO (dl_pagesize));
+  _dl_diagnostics_print_labeled_string ("dl_platform", GLRO (dl_platform));
+  _dl_diagnostics_print_labeled_string
+    ("dl_profile_output", GLRO (dl_profile_output));
+  _dl_diagnostics_print_labeled_value
+    ("dl_string_platform", _dl_string_platform ( GLRO (dl_platform)));
+
+  _dl_diagnostics_print_labeled_string ("dso.ld", LD_SO);
+  _dl_diagnostics_print_labeled_string ("dso.libc", LIBC_SO);
+
+  print_environ (environ);
+  print_paths ();
+  print_version ();
+
+  _dl_diagnostics_kernel ();
+  _dl_diagnostics_cpu ();
+
+  _exit (EXIT_SUCCESS);
+}

elf/dl-diagnostics.h

@@ -0,0 +1,46 @@
+/* Interfaces for printing diagnostics in ld.so.
+   Copyright (C) 2021 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 _DL_DIAGNOSTICS_H
+#define _DL_DIAGNOSTICS_H
+
+#include <stdint.h>
+
+/* Write the null-terminated string to standard output, surrounded in
+   quotation marks.  */
+void _dl_diagnostics_print_string (const char *s) attribute_hidden;
+
+/* Like _dl_diagnostics_print_string, but add a LABEL= prefix, and a
+   newline character as a suffix.  */
+void _dl_diagnostics_print_labeled_string (const char *label, const char *s)
+  attribute_hidden;
+
+/* Print LABEL=VALUE to standard output, followed by a newline
+   character.  */
+void _dl_diagnostics_print_labeled_value (const char *label, uint64_t value)
+  attribute_hidden;
+
+/* Print diagnostics data for the kernel.  Called from
+   _dl_print_diagnostics.  */
+void _dl_diagnostics_kernel (void) attribute_hidden;
+
+/* Print diagnostics data for the CPU(s).  Called from
+   _dl_print_diagnostics.  */
+void _dl_diagnostics_cpu (void) attribute_hidden;
+
+#endif /* _DL_DIAGNOSTICS_H */

elf/dl-main.h

@@ -63,7 +63,7 @@ struct audit_list
 enum rtld_mode
   {
     rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
-    rtld_mode_list_tunables, rtld_mode_help,
+    rtld_mode_list_tunables, rtld_mode_list_diagnostics, rtld_mode_help,
   };
 
 /* Aggregated state information extracted from environment variables
@@ -121,4 +121,7 @@ _Noreturn void _dl_version (void) attribute_hidden;
 _Noreturn void _dl_help (const char *argv0, struct dl_main_state *state)
   attribute_hidden;
 
+/* Print a diagnostics dump.  */
+_Noreturn void _dl_print_diagnostics (char **environ) attribute_hidden;
+
 #endif /* _DL_MAIN */

elf/dl-usage.c

@@ -261,6 +261,7 @@ setting environment variables (which would be inherited by subprocesses).\n\
   --list-tunables       list all tunables with minimum and maximum values\n"
 #endif
 "\
+  --list-diagnostics    list diagnostics information\n\
   --help                display this help and exit\n\
   --version             output version information and exit\n\
 \n\

elf/rtld.c

@@ -141,6 +141,7 @@ static void dl_main_state_init (struct dl_main_state *state);
 /* Process all environments variables the dynamic linker must recognize.
    Since all of them start with `LD_' we are a bit smarter while finding
    all the entries.  */
+extern char **_environ attribute_hidden;
 static void process_envvars (struct dl_main_state *state);
 
 #ifdef DL_ARGV_NOT_RELRO
@@ -1287,6 +1288,14 @@ dl_main (const ElfW(Phdr) *phdr,
 	    ++_dl_argv;
 	  }
 #endif
+	else if (! strcmp (_dl_argv[1], "--list-diagnostics"))
+	  {
+	    state.mode = rtld_mode_list_diagnostics;
+
+	    ++_dl_skip_args;
+	    --_dl_argc;
+	    ++_dl_argv;
+	  }
 	else if (strcmp (_dl_argv[1], "--help") == 0)
 	  {
 	    state.mode = rtld_mode_help;
@@ -1315,6 +1324,9 @@ dl_main (const ElfW(Phdr) *phdr,
 	}
 #endif
 
+      if (state.mode == rtld_mode_list_diagnostics)
+	_dl_print_diagnostics (_environ);
+
       /* If we have no further argument the program was called incorrectly.
 	 Grant the user some education.  */
       if (_dl_argc < 2)
@@ -2649,12 +2661,6 @@ a filename can be specified using the LD_DEBUG_OUTPUT environment variable.\n");
     }
 }
 
-/* Process all environments variables the dynamic linker must recognize.
-   Since all of them start with `LD_' we are a bit smarter while finding
-   all the entries.  */
-extern char **_environ attribute_hidden;
-
-
 static void
 process_envvars (struct dl_main_state *state)
 {

sysdeps/unix/sysv/linux/dl-diagnostics-kernel.c

@@ -0,0 +1,77 @@
+/* Print kernel diagnostics data in ld.so.  Linux version.
+   Copyright (C) 2021 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 <dl-diagnostics.h>
+#include <ldsodefs.h>
+#include <sys/utsname.h>
+
+/* Dump the auxiliary vector to standard output.  */
+static void
+print_auxv (void)
+{
+  /* See _dl_show_auxv.  The code below follows the general output
+     format for diagnostic dumps.  */
+  unsigned int index = 0;
+  for (ElfW(auxv_t) *av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
+    {
+      _dl_printf ("auxv[0x%x].a_type=0x%lx\n"
+                  "auxv[0x%x].a_val=",
+                  index, (unsigned long int) av->a_type, index);
+      if (av->a_type == AT_EXECFN
+          || av->a_type == AT_PLATFORM
+          || av->a_type == AT_BASE_PLATFORM)
+        /* The address of the strings is not useful at all, so print
+           the strings themselvs.  */
+        _dl_diagnostics_print_string ((const char *) av->a_un.a_val);
+      else
+        _dl_printf ("0x%lx", (unsigned long int) av->a_un.a_val);
+      _dl_printf ("\n");
+      ++index;
+    }
+}
+
+/* Print one uname entry.  */
+static void
+print_utsname_entry (const char *field, const char *value)
+{
+  _dl_printf ("uname.");
+  _dl_diagnostics_print_labeled_string (field, value);
+}
+
+/* Print information from uname, including the kernel version.  */
+static void
+print_uname (void)
+{
+  struct utsname uts;
+  if (__uname (&uts) == 0)
+    {
+      print_utsname_entry ("sysname", uts.sysname);
+      print_utsname_entry ("nodename", uts.nodename);
+      print_utsname_entry ("release", uts.release);
+      print_utsname_entry ("version", uts.version);
+      print_utsname_entry ("machine", uts.machine);
+      print_utsname_entry ("domainname", uts.domainname);
+    }
+}
+
+void
+_dl_diagnostics_kernel (void)
+{
+  print_auxv ();
+  print_uname ();
+}