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Message-Id: <20200406175843.944022-1-harald@redhat.com>
Date: Mon, 6 Apr 2020 19:58:43 +0200
From: harald@...hat.com
To: musl@...ts.openwall.com
Cc: Harald Hoyer <harald@...hat.com>
Subject: [PATCH] Enable linking to a static position independent executable
From: Harald Hoyer <harald@...hat.com>
This also enables address space layout randomization (ASLR).
$ cat hello.c
int main()
{
printf("main = 0x%lxd\n", main);
return 0;
}
$ gcc -static-pie -o hello hello.c -specs musl-gcc.specs
$ ldd hello
statically linked
$ file hello
hello: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=24fe0d02b0558dc37b8ae2268878b118804ae72d, with debug_info, not stripped
$ ./hello
main = 0x7f858c4e72b9d
$ ./hello
main = 0x7f0854d312b9d
$ ./hello
main = 0x7f7179a1d2b9d
$ ./hello
main = 0x7f37f981b2b9d
$ readelf -l hello
Elf file type is DYN (Shared object file)
Entry point 0x1058
There are 9 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x00000000000003c0 0x00000000000003c0 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000002cce 0x0000000000002cce R E 0x1000
LOAD 0x0000000000004000 0x0000000000004000 0x0000000000004000
0x0000000000001550 0x0000000000001550 R 0x1000
LOAD 0x0000000000005e50 0x0000000000006e50 0x0000000000006e50
0x00000000000002e0 0x00000000000009a0 RW 0x1000
DYNAMIC 0x0000000000005e70 0x0000000000006e70 0x0000000000006e70
0x0000000000000170 0x0000000000000170 RW 0x8
NOTE 0x0000000000000238 0x0000000000000238 0x0000000000000238
0x0000000000000024 0x0000000000000024 R 0x4
GNU_EH_FRAME 0x0000000000004b60 0x0000000000004b60 0x0000000000004b60
0x00000000000001ec 0x00000000000001ec R 0x4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 0x10
GNU_RELRO 0x0000000000005e50 0x0000000000006e50 0x0000000000006e50
0x00000000000001b0 0x00000000000001b0 R 0x1
Section to Segment mapping:
Segment Sections...
00 .note.gnu.build-id .gnu.hash .dynsym .dynstr .rela.dyn
01 .init .plt .text .fini
02 .rodata .eh_frame_hdr .eh_frame
03 .init_array .fini_array .data.rel.ro .dynamic .got .got.plt .data .bss
04 .dynamic
05 .note.gnu.build-id
06 .eh_frame_hdr
07
08 .init_array .fini_array .data.rel.ro .dynamic .got
---
tools/musl-gcc.specs.sh | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/tools/musl-gcc.specs.sh b/tools/musl-gcc.specs.sh
index 30492574..7e7ae562 100644
--- a/tools/musl-gcc.specs.sh
+++ b/tools/musl-gcc.specs.sh
@@ -8,7 +8,7 @@ cat <<EOF
-nostdinc -isystem $incdir -isystem include%s %(old_cpp_options)
*cc1:
-%(cc1_cpu) -nostdinc -isystem $incdir -isystem include%s
+%(cc1_cpu) %{static-pie:-fPIE} -nostdinc -isystem $incdir -isystem include%s
*link_libgcc:
-L$libdir -L .%s
@@ -17,13 +17,13 @@ cat <<EOF
libgcc.a%s %:if-exists(libgcc_eh.a%s)
*startfile:
-%{!shared: $libdir/Scrt1.o} $libdir/crti.o crtbeginS.o%s
+%{shared:;static:$libdir/crt1.o%s; static-pie:$libdir/rcrt1.o%s; pie:$libdir/Scrt1.o%s; :$libdir/crt1.o%s} $libdir/crti.o%s %{static:crtbeginT.o%s; shared|static-pie|pie:crtbeginS.o%s; :crtbegin.o%s}
*endfile:
-crtendS.o%s $libdir/crtn.o
+%{static:crtend.o%s; shared|static-pie|pie:crtendS.o%s; :crtend.o%s} $libdir/crtn.o%s
*link:
--dynamic-linker $ldso -nostdlib %{shared:-shared} %{static:-static} %{rdynamic:-export-dynamic}
+%{!r:--build-id} --no-add-needed %{!static|static-pie:--eh-frame-hdr} --hash-style=gnu -m elf_x86_64 %{shared:-shared} %{!shared:%{!static:%{!static-pie:%{rdynamic:-export-dynamic} -dynamic-linker $ldso}} %{static:-static} %{static-pie:-static -pie --no-dynamic-linker -z text}}
*esp_link:
--
2.26.0
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