1 files changed, 62 insertions, 0 deletions

diff --git a/meta/recipes-core/glibc/glibc/0011-Quote-from-bug-1443-which-explains-what-the-patch-do.patch b/meta/recipes-core/glibc/glibc/0011-Quote-from-bug-1443-which-explains-what-the-patch-do.patch
new file mode 100644
index 0000000000..a9280b7c34
--- /dev/null
+++ b/meta/recipes-core/glibc/glibc/0011-Quote-from-bug-1443-which-explains-what-the-patch-do.patch
@@ -0,0 +1,62 @@
+From de7a7c04a92dbc5d35cb37e47c471e12784cc95e Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Wed, 18 Mar 2015 00:20:09 +0000
+Subject: [PATCH 11/29] Quote from bug 1443 which explains what the patch does
+ :
+
+  We build some random program and link it with -lust.  When we run it,
+  it dies with a SIGSEGV before reaching main().
+
+  Libust.so depends on liburcu-bp.so from the usermode-rcu package.
+  Although libust.so is not prelinked, liburcu-bp.so IS prelinked; this
+  is critical.
+
+  Libust.so uses a TLS / __thread variable that is defined in liburcu-
+  bp.so.  There are special ARM-specific relocation types that allow two
+  shared libraries to share thread-specific data.  This is critical too.
+
+  One more critical issue: although liburcu-bp.so is prelinked, we can't
+  load it at its prelinked address, because we also link against
+  librt.so, and librt.so uses that address.
+
+  The dynamic linker is forced to relink liburcu-bp.so at a different
+  address.  In the course of relinking, it processes the special ARM
+  relocation record mentioned above.  The prelinker has already filled
+  in the information, which is a short offset into a table of thread-
+  specific data that is allocated per-thread for each library that uses
+  TLS.  Because the normal behavior of a relocation is to add the symbol
+  value to an addend stored at the address being relocated, we end up
+  adding the short offset to itself, doubling it.
+
+  Now we have an awkward situation.  The libust.so library doesn't know
+  about the addend, so its TLS data for this element is correct.  The
+  liburcu-bp.so library has a different offset for the element.  When we
+  go to initialize the element for the first time in liburcu-bp.so, we
+  write the address of the result at the doubled (broken) offset.
+  Later, when we refer to the address from libust.so, we check the value
+  at the correct offset, but it's NULL, so we eat hot SIGSEGV.
+
+Upstream-Status: Pending
+
+Signed-off-by: Andrei Dinu <andrei.adrianx.dinu@intel.com>
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+---
+ sysdeps/arm/dl-machine.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/sysdeps/arm/dl-machine.h b/sysdeps/arm/dl-machine.h
+index 90856779b1..a29bb86c56 100644
+--- a/sysdeps/arm/dl-machine.h
++++ b/sysdeps/arm/dl-machine.h
+@@ -510,7 +510,7 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
+ 
+        case R_ARM_TLS_DTPOFF32:
+          if (sym != NULL)
+-           *reloc_addr += sym->st_value;
++           *reloc_addr = sym->st_value;
+          break;
+ 
+        case R_ARM_TLS_TPOFF32:
+-- 
+2.27.0
+