diff mbox series

[v3,6/7] livepatch-build: Strip transient or unneeded symbols

Message ID 20191126122511.7409-7-wipawel@amazon.de (mailing list archive)
State New, archived
Headers show
Series livepatch-build-tools: new features and fixes | expand

Commit Message

Wieczorkiewicz, Pawel Nov. 26, 2019, 12:25 p.m. UTC
In the process of creating a final hotpatch module file make sure to
strip all transient symbols that have not been caught and removed by
create-diff-object processing. For now these are only the hooks
kpatch load/unload symbols.

For all new object files that are carried along for the final linking
the transient hooks symbols are not stripped and neither are any
unneeded symbols. Strip the transient hooks symbols explicitly from
resulting object file.
Add a new option '--strip' to additionally strip all unneeded symbols
from new object files.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
---
Changed since v2:
  * Added '--strip' option for stripping unneeded symbols optionally.
---
 livepatch-build | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

Comments

Ross Lagerwall Nov. 26, 2019, 2:33 p.m. UTC | #1
On 11/26/19 12:25 PM, Pawel Wieczorkiewicz wrote:
> In the process of creating a final hotpatch module file make sure to
> strip all transient symbols that have not been caught and removed by
> create-diff-object processing. For now these are only the hooks
> kpatch load/unload symbols.
> 
> For all new object files that are carried along for the final linking
> the transient hooks symbols are not stripped and neither are any
> unneeded symbols. Strip the transient hooks symbols explicitly from
> resulting object file.
> Add a new option '--strip' to additionally strip all unneeded symbols
> from new object files.
> 
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
> ---
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
diff mbox series

Patch

diff --git a/livepatch-build b/livepatch-build
index b8a1728..9e5bad3 100755
--- a/livepatch-build
+++ b/livepatch-build
@@ -32,6 +32,7 @@  SKIP=
 DEPENDS=
 XEN_DEPENDS=
 PRELINK=
+STRIP=0
 XENSYMS=xen-syms
 
 warn() {
@@ -111,6 +112,28 @@  function build_special()
     unset LIVEPATCH_CAPTURE_DIR
 }
 
+strip_extra_symbols ()
+{
+    local -r FILE="$1"
+    local -a STRIP_CMD_OPTS=()
+    local -a SYM_PREFIX=("livepatch_load_data_"
+                         "livepatch_unload_data_"
+                         "livepatch_preapply_data_"
+                         "livepatch_apply_data_"
+                         "livepatch_postapply_data_"
+                         "livepatch_prerevert_data_"
+                         "livepatch_revert_data_"
+                         "livepatch_postrevert_data_")
+
+    STRIP_CMD_OPTS+=("-w")
+    for sym in "${SYM_PREFIX[@]}"; do
+        STRIP_CMD_OPTS+=("-N")
+        STRIP_CMD_OPTS+=("\"${sym}*\"")
+    done
+
+    strip "${STRIP_CMD_OPTS[@]}" "$FILE"
+}
+
 function create_patch()
 {
     echo "Extracting new and modified ELF sections..."
@@ -150,6 +173,7 @@  function create_patch()
     NEW_FILES=$(comm -23 <(cd patched/xen && find . -type f -name '*.o' | sort) <(cd original/xen && find . -type f -name '*.o' | sort))
     for i in $NEW_FILES; do
         cp "patched/$i" "output/$i"
+        [[ $STRIP -eq 1 ]] && strip --strip-unneeded "output/$i"
         CHANGED=1
     done
 
@@ -176,6 +200,8 @@  function create_patch()
         "${TOOLSDIR}"/prelink $debugopt output.o "${PATCHNAME}.livepatch" "$XENSYMS" &>> "${OUTPUT}/prelink.log" || die
     fi
 
+    strip_extra_symbols "${PATCHNAME}.livepatch"
+
     objcopy --add-section .livepatch.depends=depends.bin "${PATCHNAME}.livepatch"
     objcopy --set-section-flags .livepatch.depends=alloc,readonly "${PATCHNAME}.livepatch"
 
@@ -198,11 +224,12 @@  usage() {
     echo "        --depends          Required build-id" >&2
     echo "        --xen-depends      Required Xen build-id" >&2
     echo "        --prelink          Prelink" >&2
+    echo "        --strip            Remove all symbols that are not needed for relocation processing." >&2
 }
 
 find_tools || die "can't find supporting tools"
 
-options=$(getopt -o hs:p:c:o:j:k:d -l "help,srcdir:,patch:,config:,output:,cpus:,skip:,debug,xen-debug,xen-syms:,depends:,xen-depends:,prelink" -- "$@") || die "getopt failed"
+options=$(getopt -o hs:p:c:o:j:k:d -l "help,srcdir:,patch:,config:,output:,cpus:,skip:,debug,xen-debug,xen-syms:,depends:,xen-depends:,prelink,strip" -- "$@") || die "getopt failed"
 
 eval set -- "$options"
 
@@ -270,6 +297,10 @@  while [[ $# -gt 0 ]]; do
             PRELINK=--resolve
             shift
             ;;
+        --strip)
+            STRIP=1
+            shift
+            ;;
         --)
             shift
             break