A recent GLIBC fix for sparc [1] made some configuration to show
an executable stack on ld.so (shown on elf/check-execstack testcase
failure).
It is because with generated sparc toolchain from build-many-glibcs.py
(a GLIBC script to produce cross-compiling toolchains) the minimum
supported sparc32 version is pre-v9 and it requires a software
implementation of '.udiv'. Since now we are using libgcc.a one instead,
it must have the '.note.GNU-stack' so linker can properly set the stack non
executable.
>From a build using a toolchain from build-many-glibcs.py:
elf/librtld.os.map
[...]
.../sparc64-glibc-linux-gnu/6.2.1/32/libgcc.a(_divsi3.o)
.../sparc64-glibc-linux-gnu/6.2.1/32/libgcc.a(_udivdi3.o) (.udiv)
.../sparc64-glibc-linux-gnu/6.2.1/32/libgcc.a(_clz.o)
.../lib/gcc/sparc64-glibc-linux-gnu/6.2.1/32/libgcc.a(_udivdi3.o) (__clz_tab)
[...]
And dumping _udivdi3.o section headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS 00000000 000034 0002b0 00 AX 0 0 4
[ 2] .data PROGBITS 00000000 0002e4 000000 00 WA 0 0 1
[ 3] .bss NOBITS 00000000 0002e4 000000 00 WA 0 0 1
[ 4] .debug_line PROGBITS 00000000 0002e4 00010d 00 0 0 1
[ 5] .rela.debug_line RELA 00000000 0007c0 00000c 0c I 12 4 4
[ 6] .debug_info PROGBITS 00000000 0003f1 0000ab 00 0 0 1
[ 7] .rela.debug_info RELA 00000000 0007cc 000030 0c I 12 6 4
[ 8] .debug_abbrev PROGBITS 00000000 00049c 000014 00 0 0 1
[ 9] .debug_aranges PROGBITS 00000000 0004b0 000020 00 0 0 8
[10] .rela.debug_arang RELA 00000000 0007fc 000018 0c I 12 9 4
[11] .shstrtab STRTAB 00000000 000814 000070 00 0 0 1
[12] .symtab SYMTAB 00000000 0004d0 000220 10 13 32 4
[13] .strtab STRTAB 00000000 0006f0 0000cf 00 0 0 1
I am not seeing this on a native gcc build which I configured with:
' --with-arch-directory=sparc64 --enable-multiarch --enable-targets=all
--with-cpu-32=ultrasparc --with-long-double-128 --enable-multilib'
Both libgcc's __udivdi3 and __umoddi3 do not pull .udiv since for this libgcc
build
both are using hardware instructions:
elf/librtld.os.map
/home/azanella/gcc/install/lib/gcc/sparc64-linux-gnu/6.3.1/32/libgcc.a(_udivdi3.o)
/home/azanella/glibc/glibc-git-build-sparcv9/elf/dl-allobjs.os (__udivdi3)
/home/azanella/gcc/install/lib/gcc/sparc64-linux-gnu/6.3.1/32/libgcc.a(_umoddi3.o)
/home/azanella/glibc/glibc-git-build-sparcv9/elf/dl-allobjs.os (__umoddi3)
This patch adds them missing noexectack on sparc assembly implementation. I saw
no regression on gcc testsuite and it fixes the regression on GLIBC side.
libgcc/
* config/sparc/lb1spc.S [__ELF__ && __linux__]: Emit .note.GNU-stack
section for a non-executable stack.
[1]
https://sourceware.org/git/?p=glibc.git;a=commit;h=bdc543e338281da051b3dc06eae96c330a485ce6
---
libgcc/ChangeLog | 5 +++++
libgcc/config/sparc/lb1spc.S | 6 ++++++
2 files changed, 11 insertions(+)
diff --git a/libgcc/config/sparc/lb1spc.S b/libgcc/config/sparc/lb1spc.S
index b60bd57..e693864 100644
--- a/libgcc/config/sparc/lb1spc.S
+++ b/libgcc/config/sparc/lb1spc.S
@@ -5,6 +5,12 @@
slightly edited to match the desired calling convention, and also to
optimize them for our purposes. */
+/* An executable stack is *not* required for these functions. */
+#if defined(__ELF__) && defined(__linux__)
+.section .note.GNU-stack,"",%progbits
+.previous
+#endif
+
#ifdef L_mulsi3
.text
.align 4
--
2.7.4
