From 003a27e8195470f470f4d9384ca70d4e9fc8bd1b Mon Sep 17 00:00:00 2001
From: Nick Alcock <nick.alcock@oracle.com>
Date: Mon, 26 Dec 2016 10:08:34 +0100
Subject: Initialize the stack guard earlier when linking statically [BZ #7065]

The address of the stack canary is stored in a per-thread variable,
which means that we must ensure that the TLS area is intialized before
calling any -fstack-protector'ed functions.  For dynamically linked
applications, we ensure this (in a later patch) by disabling
-fstack-protector for the whole dynamic linker, but for static
applications, the AT_ENTRY address is called directly by the kernel, so
we must deal with the problem differently.

In static appliations, __libc_setup_tls performs the TCB setup and TLS
initialization, so this commit arranges for it to be called early and
unconditionally.  The call (and the stack guard initialization) is
before the DL_SYSDEP_OSCHECK hook, which if set will probably call
functions which are stack-protected (it does on Linux and NaCL too).  We
also move apply_irel up, so that we can still safely call functions that
require ifuncs while in __libc_setup_tls (though if stack-protection is
enabled we still have to avoid calling functions that are not
stack-protected at this stage).
---
 csu/libc-start.c | 29 +++++++++++++++--------------
 csu/libc-tls.c   | 17 ++++-------------
 2 files changed, 19 insertions(+), 27 deletions(-)

(limited to 'csu')

diff --git a/csu/libc-start.c b/csu/libc-start.c
index 99c040a..cc59073 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -29,7 +29,6 @@ extern int __libc_multiple_libcs;
 #include <tls.h>
 #ifndef SHARED
 # include <dl-osinfo.h>
-extern void __pthread_initialize_minimal (void);
 # ifndef THREAD_SET_STACK_GUARD
 /* Only exported for architectures that don't store the stack guard canary
    in thread local area.  */
@@ -175,22 +174,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
         }
     }
 
-# ifdef DL_SYSDEP_OSCHECK
-  if (!__libc_multiple_libcs)
-    {
-      /* This needs to run to initiliaze _dl_osversion before TLS
-	 setup might check it.  */
-      DL_SYSDEP_OSCHECK (__libc_fatal);
-    }
-# endif
-
   /* Perform IREL{,A} relocations.  */
   apply_irel ();
 
-  /* Initialize the thread library at least a bit since the libgcc
-     functions are using thread functions if these are available and
-     we need to setup errno.  */
-  __pthread_initialize_minimal ();
+  /* The stack guard goes into the TCB, so initialize it early.  */
+  __libc_setup_tls ();
 
   /* Set up the stack checker's canary.  */
   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
@@ -200,6 +188,19 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   __stack_chk_guard = stack_chk_guard;
 # endif
 
+# ifdef DL_SYSDEP_OSCHECK
+  if (!__libc_multiple_libcs)
+    {
+      /* This needs to run to initiliaze _dl_osversion before TLS
+	 setup might check it.  */
+      DL_SYSDEP_OSCHECK (__libc_fatal);
+    }
+# endif
+
+  /* Initialize libpthread if linked in.  */
+  if (__pthread_initialize_minimal != NULL)
+    __pthread_initialize_minimal ();
+
   /* Set up the pointer guard value.  */
   uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
 							 stack_chk_guard);
diff --git a/csu/libc-tls.c b/csu/libc-tls.c
index 8f92234..454f165 100644
--- a/csu/libc-tls.c
+++ b/csu/libc-tls.c
@@ -102,14 +102,14 @@ init_static_tls (size_t memsz, size_t align)
 }
 
 void
-__libc_setup_tls (size_t tcbsize, size_t tcbalign)
+__libc_setup_tls (void)
 {
   void *tlsblock;
   size_t memsz = 0;
   size_t filesz = 0;
   void *initimage = NULL;
   size_t align = 0;
-  size_t max_align = tcbalign;
+  size_t max_align = TCB_ALIGNMENT;
   size_t tcb_offset;
   const ElfW(Phdr) *phdr;
 
@@ -142,9 +142,9 @@ __libc_setup_tls (size_t tcbsize, size_t tcbalign)
      _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign
      and dl_tls_static_align.  */
   tcb_offset = roundup (memsz + GL(dl_tls_static_size), max_align);
-  tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
+  tlsblock = __sbrk (tcb_offset + TLS_INIT_TCB_SIZE + max_align);
 #elif TLS_DTV_AT_TP
-  tcb_offset = roundup (tcbsize, align ?: 1);
+  tcb_offset = roundup (TLS_INIT_TCB_SIZE, align ?: 1);
   tlsblock = __sbrk (tcb_offset + memsz + max_align
 		     + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
   tlsblock += TLS_PRE_TCB_SIZE;
@@ -215,12 +215,3 @@ __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 
   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 }
-
-/* This is the minimal initialization function used when libpthread is
-   not used.  */
-void
-__attribute__ ((weak))
-__pthread_initialize_minimal (void)
-{
-  __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
-}
-- 
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