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My system (Fedora 12 x86_64) supports the GNU non-executable stack note, but the configure script is not detecting it correctly. The test program used to check for this note causes a compiler error which causes configure to incorrectly determine the system does not support this feature. A better test program is needed to determine if the non-executable stack is actually supported.

This problem turns out to be the root cause of some strange behavior I encountered, which I repeat here in case others have a similar problem. I was attempting to verify that my programs were being dynamically linked using ldd, but ldd was reporting that the binary was not a dynamically linked executable. ldd was having a problem due to SELinux which was not happy with the executable stack on the programs generated by ghc. Looking through past tickets I found #703 (closed) which says that ghc does generate code using the non-executable stack note. Thus I found that the build system was not correctly setting the value.

Now to the details of the problem. The configure.ac contains the following check to see if the system supports the non-executable stack note.

827 dnl *** check for GNU non-executable stack note support (ELF only)
828 dnl     (.section .note.GNU-stack,"",@progbits)
829 
830 AC_MSG_CHECKING(for GNU non-executable stack support)
831 AC_COMPILE_IFELSE(
832     [AC_LANG_PROGRAM([__asm__ (".section .note.GNU-stack,\"\",@progbits");], [0])],
833     [AC_MSG_RESULT(yes)
834      AC_DEFINE([HAVE_GNU_NONEXEC_STACK],[1],
835                [Define to 1 if GNU non-executable stack notes are supported.])
836     ],
837     [AC_MSG_RESULT(no)])

On my system (Fedora 12) this test generates the assembler error shown which causes configure to incorrectly say that the compiler does not support the non-executable stack note.

$ /usr/lib64/ccache/gcc -c -g -O2 conftest.c
/tmp/ccohqUvf.s: Assembler messages:
/tmp/ccohqUvf.s:126: Error: can't resolve `.note.GNU-stack' {.note.GNU-stack section} - `.Ltext0' {.text section}

I believe the assembler error is related to the debug info that is generating references to the label containing the .section .note.GNU-stack. I've included the the generated assembly below for reference. If the -g flag is removed the assembler error goes away.

Not being an autoconf expert I can think of two options for a better autoconf test.

1. Don't use -g when compiling the current test program.
2. Use a variation of $ gcc -Wa,-al,--noexecstack t.c | grep '.note.GNU-stack'

$ /usr/lib64/ccache/gcc -c -g -O2 -S conftest.c
$ cat conftest.s
	.file	"t.c"
	.section	.debug_abbrev,"",@progbits
.Ldebug_abbrev0:
	.section	.debug_info,"",@progbits
.Ldebug_info0:
	.section	.debug_line,"",@progbits
.Ldebug_line0:
	.text
.Ltext0:
#APP
	.section .note.GNU-stack,"",@progbits
#NO_APP
	.p2align 4,,15
.globl main
	.type	main, @function
main:
.LFB0:
	.file 1 "t.c"
	.loc 1 106 0
	.cfi_startproc
	.loc 1 110 0
	xorl	%eax, %eax
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
.Letext0:
	.section	.debug_info
	.long	0x4f
	.value	0x3
	.long	.Ldebug_abbrev0
	.byte	0x8
	.uleb128 0x1
	.long	.LASF0
	.byte	0x1
	.string	"t.c"
	.long	.LASF1
	.quad	.Ltext0
	.quad	.Letext0
	.long	.Ldebug_line0
	.uleb128 0x2
	.byte	0x1
	.long	.LASF2
	.byte	0x1
	.byte	0x69
	.long	0x4b
	.quad	.LFB0
	.quad	.LFE0
	.byte	0x1
	.byte	0x9c
	.uleb128 0x3
	.byte	0x4
	.byte	0x5
	.string	"int"
	.byte	0x0
	.section	.debug_abbrev
	.uleb128 0x1
	.uleb128 0x11
	.byte	0x1
	.uleb128 0x25
	.uleb128 0xe
	.uleb128 0x13
	.uleb128 0xb
	.uleb128 0x3
	.uleb128 0x8
	.uleb128 0x1b
	.uleb128 0xe
	.uleb128 0x11
	.uleb128 0x1
	.uleb128 0x12
	.uleb128 0x1
	.uleb128 0x10
	.uleb128 0x6
	.byte	0x0
	.byte	0x0
	.uleb128 0x2
	.uleb128 0x2e
	.byte	0x0
	.uleb128 0x3f
	.uleb128 0xc
	.uleb128 0x3
	.uleb128 0xe
	.uleb128 0x3a
	.uleb128 0xb
	.uleb128 0x3b
	.uleb128 0xb
	.uleb128 0x49
	.uleb128 0x13
	.uleb128 0x11
	.uleb128 0x1
	.uleb128 0x12
	.uleb128 0x1
	.uleb128 0x40
	.uleb128 0xa
	.byte	0x0
	.byte	0x0
	.uleb128 0x3
	.uleb128 0x24
	.byte	0x0
	.uleb128 0xb
	.uleb128 0xb
	.uleb128 0x3e
	.uleb128 0xb
	.uleb128 0x3
	.uleb128 0x8
	.byte	0x0
	.byte	0x0
	.byte	0x0
	.section	.debug_pubnames,"",@progbits
	.long	0x17
	.value	0x2
	.long	.Ldebug_info0
	.long	0x53
	.long	0x2d
	.string	"main"
	.long	0x0
	.section	.debug_aranges,"",@progbits
	.long	0x2c
	.value	0x2
	.long	.Ldebug_info0
	.byte	0x8
	.byte	0x0
	.value	0x0
	.value	0x0
	.quad	.Ltext0
	.quad	.Letext0-.Ltext0
	.quad	0x0
	.quad	0x0
	.section	.debug_str,"MS",@progbits,1
.LASF1:
	.string	"/home/dave/tmp"
.LASF0:
	.string	"GNU C 4.4.2 20091027 (Red Hat 4.4.2-7)"
.LASF2:
	.string	"main"
	.ident	"GCC: (GNU) 4.4.2 20091027 (Red Hat 4.4.2-7)"
	.section	.note.GNU-stack,"",@progbits

Trac metadata

Trac field	Value
Version	6.13
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture