[PATCH v2] ld.so: Decorate BSS mappings

[Petr Malat]

Decorate BSS mappings with [anon: glibc: .bss <file>], for example
[anon: glibc: .bss /lib/libc.so.6]. The string ".bss" is already used
by bionic so use the same, but add the filename as well. If the name
would be longer than what the kernel allows, drop the directory part
of the path.

Signed-off-by: Petr Malat <oss@malat.biz>
---
 elf/dl-map-segments.h                | 25 +++++++++++++++++++++++++
 nptl/allocatestack.c                 |  4 ----
 sysdeps/generic/setvmaname.h         |  4 ++++
 sysdeps/unix/sysv/linux/setvmaname.h |  4 ++++
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
index 203b6c7b0b..dfd1685ebb 100644
--- a/elf/dl-map-segments.h
+++ b/elf/dl-map-segments.h
@@ -18,6 +18,7 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <dl-load.h>
+#include <setvmaname.h>
 
 /* Map a segment and align it properly.  */
 
@@ -182,12 +183,36 @@ _dl_map_segments (struct link_map *l, int fd,
           if (zeroend > zeropage)
             {
               /* Map the remaining zero pages in from the zero fill FD.  */
+              char bssname[ANON_VMA_NAME_MAX_LEN] = " glibc: .bss";
+
               caddr_t mapat;
               mapat = __mmap ((caddr_t) zeropage, zeroend - zeropage,
                               c->prot, MAP_ANON|MAP_PRIVATE|MAP_FIXED,
                               -1, 0);
               if (__glibc_unlikely (mapat == MAP_FAILED))
                 return DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL;
+              if (l->l_name && *l->l_name)
+                {
+                  int i = strlen(bssname), j = 0;
+                  int namelen = strlen(l->l_name);
+
+                  bssname[i++] = ' ';
+                  if (namelen > sizeof(bssname) - i - 1)
+                    for (j = namelen - 1; j > 0; j--)
+                      if (l->l_name[j - 1] == '/')
+                        break;
+
+                  for (; l->l_name[j] && i < sizeof(bssname) - 1; i++, j++)
+                    {
+                      char ch = l->l_name[j];
+                      /* Replace non-printable characters and \, `, $, [ and ] */
+                      if (ch <= 0x1f || ch >= 0x7f || strchr("\\`$[]", ch))
+                        ch = '!';
+                      bssname[i] = ch;
+                    }
+                  bssname[i] = 0;
+                }
+              __set_vma_name ((void*)zeropage, zeroend - zeropage, bssname);
             }
         }
 
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 9c1a72bcf0..622c22f050 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -549,10 +549,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
   return 0;
 }
 
-/* Maximum supported name from initial kernel support, not exported
-   by user API.  */
-#define ANON_VMA_NAME_MAX_LEN 80
-
 #define SET_STACK_NAME(__prefix, __stack, __stacksize, __tid)		\
   ({									\
      char __stack_name[sizeof (__prefix) +				\
diff --git a/sysdeps/generic/setvmaname.h b/sysdeps/generic/setvmaname.h
index baca984a54..b0d6f62bfc 100644
--- a/sysdeps/generic/setvmaname.h
+++ b/sysdeps/generic/setvmaname.h
@@ -19,6 +19,10 @@
 #ifndef __SETVMANAME_H
 #define __SETVMANAME_H
 
+/* Set this to small value to not waste memory on systems, which do
+ * not support VMA name. */
+#define ANON_VMA_NAME_MAX_LEN 16
+
 static inline
 void __set_vma_name (void *start, size_t len, const char *name)
 {
diff --git a/sysdeps/unix/sysv/linux/setvmaname.h b/sysdeps/unix/sysv/linux/setvmaname.h
index 715b096799..34a09076da 100644
--- a/sysdeps/unix/sysv/linux/setvmaname.h
+++ b/sysdeps/unix/sysv/linux/setvmaname.h
@@ -19,6 +19,10 @@
 #ifndef __SETVMANAME_H
 #define __SETVMANAME_H
 
+/* Maximum supported name from initial kernel support, not exported
+   by user API.  */
+#define ANON_VMA_NAME_MAX_LEN 80
+
 /* 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)
-- 
2.39.5