patches/glibc/ports-2.12.1/340-dl_execstack-PaX-support.patch
author "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Tue Dec 13 23:32:39 2011 +0100 (2011-12-13)
branch1.13
changeset 2847 c0bf2319af08
permissions -rw-r--r--
scripts: fix dumping execution backtrace

Dumping the backtrace has been broken since changeset #652e56d6d35a:
scripts: execute each steps in a subshell

We can spawn sub-sub-shells in some cases.

The way the fault handler works is to dump the backtrace, but to avoid
printing it once for every sub-shell (which could get quite confusing),
it simply exits when it detects that it is being run in a sub-shell,
leaving to the top-level shell the work to dump the backtrace.

Because each step is executed in its own sub-shell, the variable arrays
that contain the step name, the source file and line number, are lost
when exiting the per-step sub-shell.

Hence, the backtrace is currently limited to printing only the top-level
main procedure of the shell.

Fix this thus:
- when dumping the bckatraces for the steps & the functions, remember
it was dumped, and only dump it if it was not already dumped
- at the top-level shell, print the hints

Also, rename the top-level step label.

Reported-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from 4193d6e6a17430a177fa88c287879c2c35e319f3)
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	With latest versions of glibc, a lot of apps failed on a PaX enabled
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	system with:
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		 cannot enable executable stack as shared object requires: Permission denied
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	This is due to PaX 'exec-protecting' the stack, and ld.so then trying
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	to make the stack executable due to some libraries not containing the
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	PT_GNU_STACK section.  Bug #32960.  <azarah@gentoo.org> (12 Nov 2003).
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	Patch also NPTL. Bug #116086. <kevquinn@gentoo.org> (20 Dec 2005).
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diff -durN glibc-2.12.1.orig/nptl/allocatestack.c glibc-2.12.1/nptl/allocatestack.c
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--- glibc-2.12.1.orig/nptl/allocatestack.c	2009-01-29 21:34:16.000000000 +0100
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+++ glibc-2.12.1/nptl/allocatestack.c	2009-11-13 00:50:33.000000000 +0100
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@@ -329,7 +329,8 @@
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 # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
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 #endif
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   if (mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
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-    return errno;
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+    if (errno != EACCES) /* PAX is enabled */
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+    	return errno;
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   return 0;
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 }
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diff -durN glibc-2.12.1.orig/sysdeps/unix/sysv/linux/dl-execstack.c glibc-2.12.1/sysdeps/unix/sysv/linux/dl-execstack.c
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--- glibc-2.12.1.orig/sysdeps/unix/sysv/linux/dl-execstack.c	2006-01-08 09:21:15.000000000 +0100
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+++ glibc-2.12.1/sysdeps/unix/sysv/linux/dl-execstack.c	2009-11-13 00:50:33.000000000 +0100
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@@ -63,7 +63,10 @@
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       else
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 # endif
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 	{
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-	  result = errno;
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+	  if (errno == EACCES)  /* PAX is enabled */
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+	    result = 0;
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+	  else
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+	    result = errno;
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 	  goto out;
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 	}
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     }
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@@ -89,7 +92,12 @@
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 	page -= size;
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       else
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 	{
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-	  if (errno != ENOMEM)	/* Unexpected failure mode.  */
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+	  if (errno == EACCES)		/* PAX is enabled */
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+	    {
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+	      result = 0;
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+	      goto out;
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+	    }
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+	  else if (errno != ENOMEM)	/* Unexpected failure mode.  */
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 	    {
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 	      result = errno;
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 	      goto out;
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@@ -115,7 +123,12 @@
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 	page += size;
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       else
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 	{
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-	  if (errno != ENOMEM)	/* Unexpected failure mode.  */
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+	  if (errno == EACCES)		/* PAX is enabled */
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+	    {
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+	      result = 0;
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+	      goto out;
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+	    }
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+	  else if (errno != ENOMEM)	/* Unexpected failure mode.  */
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 	    {
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 	      result = errno;
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 	      goto out;