This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
[PATCH v2] Improve IFUNC check
On 2020-02-08, Aurelien Jarno wrote:
On 2020-02-06 10:53, Fangrui Song wrote:
On 2020-02-06, Aurelien Jarno wrote:
> Hi,
>
> On 2020-02-04 22:09, Fangrui Song wrote:
> > GNU ld's RISCV port does not support IFUNC. ld -no-pie produces no
> > relocation and the test passed incorrectly. Be more rigid by testing
> > IRELATIVE explicitly.
>
> Thanks for your patch and sorry for the time to answer, I was testing it
> on many architectures. First of all I confirm it fixes the issue when
> building glibc with PIE on mips* and riscv64. I also confirm it
> introduces no regression on aarch64, armv5, armv7, hppa, m68k, powerpc,
> ppc64, ppc64le, s390x and x86_64.
>
> However it wrongly detects that IFUNC is not supported on sparc64 when
> PIE is not in use. Here is the output of of readelf for the non-PIE
> case:
>
> | Relocation section '.rela.dyn' at offset 0x110 contains 1 entry:
> | Offset Info Type Sym. Value Sym. Name + Addend
> | 000000200280 0000000000f8 R_SPARC_JMP_IREL 100128
sparc64 -no-pie does not produce an R_SPARC_IRELATIVE. This looks weird.
All other archs emit an R_*_IRELATIVE.
Can you dump the assembly (including .text and .[i]plt)?
Or can someone with sparc64 experience answer why sparc64 is different
here?
Here is the dump of the .iplt section:
Disassembly of section .iplt:
0000000000200200 <.iplt>:
...
200280: 03 00 00 80 sethi %hi(0x20000), %g1
200284: 30 6f ff e7 b,a %xcc, 200220 <__start+0x1000f8>
200288: 01 00 00 00 nop
20028c: 01 00 00 00 nop
200290: 01 00 00 00 nop
200294: 01 00 00 00 nop
200298: 01 00 00 00 nop
20029c: 01 00 00 00 nop
There is no .text nor .plt section.
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://www.aurel32.net
Attached PATCH v2.
sparc64 has a non-conventional R_SPARC_JMP_IREL, along with conventional
R_SPARC_IRELATIVE.
>From 624b3a0c9e4f2f421227bb3f331723dfe807f157 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Tue, 4 Feb 2020 21:55:44 -0800
Subject: [PATCH] Improve IFUNC check [BZ #25506]
GNU ld does not support IFUNC but does not produces a relocation.
The test passed incorrectly. Be more rigid by testing IRELATIVE
explicitly.
---
configure | 2 +-
configure.ac | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/configure b/configure
index b959d2d988..3b98ec312f 100755
--- a/configure
+++ b/configure
@@ -4035,7 +4035,7 @@ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
-o conftest conftest.S 1>&5 2>&5; then
# Do a link to see if the backend supports IFUNC relocs.
$READELF -r conftest 1>&5
- LC_ALL=C $READELF -r conftest | grep 'no relocations' >/dev/null || {
+ LC_ALL=C $READELF -Wr conftest | grep -q 'IRELATIVE\|R_SPARC_JMP_IREL' && {
libc_cv_ld_gnu_indirect_function=yes
}
fi
diff --git a/configure.ac b/configure.ac
index 49b900c1ed..e20034f301 100644
--- a/configure.ac
+++ b/configure.ac
@@ -649,7 +649,7 @@ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
-o conftest conftest.S 1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD; then
# Do a link to see if the backend supports IFUNC relocs.
$READELF -r conftest 1>&AS_MESSAGE_LOG_FD
- LC_ALL=C $READELF -r conftest | grep 'no relocations' >/dev/null || {
+ LC_ALL=C $READELF -Wr conftest | grep -q 'IRELATIVE\|R_SPARC_JMP_IREL' && {
libc_cv_ld_gnu_indirect_function=yes
}
fi
--
2.25.0.341.g760bfbb309-goog