[PATCH] PowerPC: incorrect library search order?

[PATCH] PowerPC: incorrect library search order?

[Alexey Neyman]

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Hi,

The problem below resulted in failures of some PowerPC sample toolchains 
in crosstool-ng.

As far as I understand, the code in ld/emulparams/elf32ppccommon.sh 
attempts to use /lib32 or /lib64 if the endianness of the selected 
emulation matches the endianness of the machine, and use the directories 
with explicit endianness (such as /lib32le, /lib32be, /lib64le, 
/lib64be) otherwise. However, there are two issues with that code:

First, it checks for *host's* triplet, not target. The host may not be 
using 'le' suffix to designate its endianness - for example, it may be 
little-endian by default. It also doesn't seem to make much sense to 
check the host for default layout - why would the expected sysroot 
layout on a big-endian host differ from that on a little-endian host?

Second, the check itself is flawed: it should be checking just the CPU 
part of the triplet, not the whole string. In its current form, the 
check compares $host against "*le-*" pattern - which matches 
"x86_64-apple-darwin16.0".

This results in ld configured for powerpc64le-unknown-linux target on 
x86_64-unknown-linux host behaving as follows:
- without -m, or with -melf64lppc it searches /lib64le first
- with '-melf64ppc' it searches /lib64 first - which seems to run 
counter to the intended purpose of that code, as the target is 
configured as little-endian!

'ld' works ok with libraries in /lib (which is always searched as the 
last fallback, regardless of the host and selected emulation). Once the 
libraries are placed in /lib64 (default gcc's directory for this 
target), ld fails to find them.

This erroneous code first appeared in binutils 2.24.

Patch attached.

Regards,
Alexey.




[-- Attachment #2: 0001-Fix-library-paths-on-PowerPC.patch --]
[-- Type: text/x-patch, Size: 1549 bytes --]

From cf2cf4ea661b8527d0fe48a9ffda1b02154d0c67 Mon Sep 17 00:00:00 2001
From: Alexey Neyman <stilor@att.net>
Date: Sat, 11 Mar 2017 17:27:09 -0800
Subject: [PATCH] Fix library paths on PowerPC

First, need to match against just the CPU name, not the whole triplet.
Otherwise, the test picks up "*le-*" pattern from x86_64-apple-darwin
triplet.

Second, it should be testing for $target, not $host. Host may be
little endian by default, and the sysroot directory layout shouldn't
depend on whether it is built on LE or BE machine.

Signed-off-by: Alexey Neyman <stilor@att.net>
---
 ld/emulparams/elf32ppccommon.sh | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/ld/emulparams/elf32ppccommon.sh b/ld/emulparams/elf32ppccommon.sh
index 1f54ef8..d00cf68 100644
--- a/ld/emulparams/elf32ppccommon.sh
+++ b/ld/emulparams/elf32ppccommon.sh
@@ -44,11 +44,11 @@ fi
 
 # Look for 64 bit target libraries in /lib64, /usr/lib64 etc., first.
 # Similarly, look for 32 bit libraries in /lib32, /usr/lib32 etc.
-case "$host":"$EMULATION_NAME" in
-  *le-*:*64lppc*) LIBPATH_SUFFIX=64 ;;
-  *le-*:*32lppc*) LIBPATH_SUFFIX=32 ;;
-  *le-*:*64*) LIBPATH_SUFFIX=64be ;;
-  *le-*:*32*) LIBPATH_SUFFIX=32be ;;
+case `echo "$target" | sed -e 's/-.*//'`:"$EMULATION_NAME" in
+  *le:*64lppc*) LIBPATH_SUFFIX=64 ;;
+  *le:*32lppc*) LIBPATH_SUFFIX=32 ;;
+  *le:*64*) LIBPATH_SUFFIX=64be ;;
+  *le:*32*) LIBPATH_SUFFIX=32be ;;
   *:*64lppc*) LIBPATH_SUFFIX=64le ;;
   *:*32lppc*) LIBPATH_SUFFIX=32le ;;
   *:*64*) LIBPATH_SUFFIX=64 ;;
-- 
2.9.3

Re: [PATCH] PowerPC: incorrect library search order?

[Alan Modra]

On Sun, Mar 12, 2017 at 08:49:46PM -0700, Alexey Neyman wrote:
> First, need to match against just the CPU name, not the whole triplet.
> Otherwise, the test picks up "*le-*" pattern from x86_64-apple-darwin
> triplet.

I wonder how many more of these are lurking.  I fixed some with
4811ccb48.

> Second, it should be testing for $target, not $host. Host may be
> little endian by default, and the sysroot directory layout shouldn't
> depend on whether it is built on LE or BE machine.

Thanks.  Applied with this changelog.

2017-03-13  Alexey Neyman  <stilor@att.net>

	* emulparams/elf32ppccommon.sh (LIBPATH_SUFFIX): Set from target
	cpu, not host.

-- 
Alan Modra
Australia Development Lab, IBM

Re: [PATCH] PowerPC: incorrect library search order?

[Andreas Schwab]

On Mär 12 2017, Alexey Neyman <stilor@att.net> wrote:

> diff --git a/ld/emulparams/elf32ppccommon.sh b/ld/emulparams/elf32ppccommon.sh
> index 1f54ef8..d00cf68 100644
> --- a/ld/emulparams/elf32ppccommon.sh
> +++ b/ld/emulparams/elf32ppccommon.sh
> @@ -44,11 +44,11 @@ fi
>  
>  # Look for 64 bit target libraries in /lib64, /usr/lib64 etc., first.
>  # Similarly, look for 32 bit libraries in /lib32, /usr/lib32 etc.
> -case "$host":"$EMULATION_NAME" in
> -  *le-*:*64lppc*) LIBPATH_SUFFIX=64 ;;
> -  *le-*:*32lppc*) LIBPATH_SUFFIX=32 ;;
> -  *le-*:*64*) LIBPATH_SUFFIX=64be ;;
> -  *le-*:*32*) LIBPATH_SUFFIX=32be ;;
> +case `echo "$target" | sed -e 's/-.*//'`:"$EMULATION_NAME" in

That's $target_cpu.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] PowerPC: incorrect library search order?

[Alan Modra]

On Mon, Mar 13, 2017 at 10:20:40AM +0100, Andreas Schwab wrote:
> On Mär 12 2017, Alexey Neyman <stilor@att.net> wrote:
> > +case `echo "$target" | sed -e 's/-.*//'`:"$EMULATION_NAME" in
> 
> That's $target_cpu.

So it is, but target_cpu isn't passed to genscripts.sh.

-- 
Alan Modra
Australia Development Lab, IBM