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authorFlorian Weimer <fweimer@redhat.com>2020-12-16 15:09:52 +0100
committerFlorian Weimer <fweimer@redhat.com>2020-12-16 15:13:40 +0100
commit29a4db291b1282f4088e549391d86b6b470f22be (patch)
tree7aeec66b84cf95b0402816617a8f9b9c0418d2d3
parente7570f4131a6af9405af7b4fd1c31de807e7cf68 (diff)
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malloc: Use __libc_initial to detect an inner libc
The secondary/non-primary/inner libc (loaded via dlmopen, LD_AUDIT,
static dlopen) must not use sbrk to allocate member because that would
interfere with allocations in the outer libc.  On Linux, this does not
matter because sbrk itself was changed to fail in secondary libcs.

 _dl_addr occasionally shows up in profiles, but had to be used before
because __libc_multiple_libs was unreliable.  So this change achieves
a slight reduction in startup time.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
-rw-r--r--malloc/arena.c13
-rw-r--r--malloc/malloc.c2
2 files changed, 7 insertions, 8 deletions
diff --git a/malloc/arena.c b/malloc/arena.c
index 202daf15b0..3c9c0ecd86 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -294,14 +294,11 @@ ptmalloc_init (void)
   __malloc_initialized = 0;
 
 #ifdef SHARED
-  /* In case this libc copy is in a non-default namespace, never use brk.
-     Likewise if dlopened from statically linked program.  */
-  Dl_info di;
-  struct link_map *l;
-
-  if (_dl_open_hook != NULL
-      || (_dl_addr (ptmalloc_init, &di, &l, NULL) != 0
-          && l->l_ns != LM_ID_BASE))
+  /* In case this libc copy is in a non-default namespace, never use
+     brk.  Likewise if dlopened from statically linked program.  The
+     generic sbrk implementation also enforces this, but it is not
+     used on Hurd.  */
+  if (!__libc_initial)
     __morecore = __failing_morecore;
 #endif
 
diff --git a/malloc/malloc.c b/malloc/malloc.c
index ec2d934595..326075e704 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -247,6 +247,8 @@
 /* For SINGLE_THREAD_P.  */
 #include <sysdep-cancel.h>
 
+#include <libc-internal.h>
+
 /*
   Debugging: