linux-kernel - [PATCH 3.16 069/370] powerpc/boot: Request no dynamic linker for boot wrapper

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Message-ID: <lsq.1489146382.889219563@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:22 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Nicholas Piggin" <npiggin@...il.com>,
        "Anton Blanchard" <anton@...ba.org>,
        "Michael Ellerman" <mpe@...erman.id.au>
Subject: [PATCH 3.16 069/370] powerpc/boot: Request no dynamic linker for
 boot wrapper

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Piggin <npiggin@...il.com>

commit ff45000fcb56b5b0f1a14a865d3541746d838a0a upstream.

The boot wrapper performs its own relocations and does not require
PT_INTERP segment. However currently we don't tell the linker that.

Prior to binutils 2.28 that works OK. But since binutils commit
1a9ccd70f9a7 ("Fix the linker so that it will not silently generate ELF
binaries with invalid program headers. Fix readelf to report such
invalid binaries.") binutils tries to create a program header segment
due to PT_INTERP, and the link fails because there is no space for it:

  ld: arch/powerpc/boot/zImage.pseries: Not enough room for program headers, try linking with -N
  ld: final link failed: Bad value

So tell the linker not to do that, by passing --no-dynamic-linker.

Reported-by: Anton Blanchard <anton@...ba.org>
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
[mpe: Drop dependency on ld-version.sh and massage change log]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/boot/wrapper | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

--- a/arch/powerpc/boot/wrapper
+++ b/arch/powerpc/boot/wrapper
@@ -144,6 +144,28 @@ case "$elfformat" in
     elf32-powerpc)	format=elf32ppc	;;
 esac
 
+ld_version()
+{
+    # Poached from scripts/ld-version.sh, but we don't want to call that because
+    # this script (wrapper) is distributed separately from the kernel source.
+    # Extract linker version number from stdin and turn into single number.
+    awk '{
+	gsub(".*\\)", "");
+	gsub(".*version ", "");
+	gsub("-.*", "");
+	split($1,a, ".");
+	print a[1]*100000000 + a[2]*1000000 + a[3]*10000;
+	exit
+    }'
+}
+
+# Do not include PT_INTERP segment when linking pie. Non-pie linking
+# just ignores this option.
+LD_VERSION=$(${CROSS}ld --version | ld_version)
+LD_NO_DL_MIN_VERSION=$(echo 2.26 | ld_version)
+if [ "$LD_VERSION" -ge "$LD_NO_DL_MIN_VERSION" ] ; then
+	nodl="--no-dynamic-linker"
+fi
 
 platformo=$object/"$platform".o
 lds=$object/zImage.lds
@@ -395,7 +417,7 @@ if [ "$platform" != "miboot" ]; then
     if [ -n "$link_address" ] ; then
         text_start="-Ttext $link_address"
     fi
-    ${CROSS}ld -m $format -T $lds $text_start $pie -o "$ofile" \
+    ${CROSS}ld -m $format -T $lds $text_start $pie $nodl -o "$ofile" \
 	$platformo $tmp $object/wrapper.a
     rm $tmp
 fi