support/check-rpath: recognise PIE

We sanity-check the host executables that they have a correct RPATH pointing to the host libraries.

This is currently done by looking for all files in $(HOST_DIR) that match the 'ELF executable' pattern (a bit more complex, but that's idea).

However, when an executable is built with -fPIE of -fpie, it no longer appears to be an 'ELF executable', but it rather looks like an 'ELF sheard object' (like if it were an library.

So, we miss those files.

It turns out that the problem is a real one, because quite a few mainline distros, expecially those based on Debian for example, have already switched to generating PIE code by default, and thus we miss on a whole class of systems..

We fix that by simply looking if we can find an ELF interpreter in each file. If we there is one, this is an ELF executable; if not, it may be anything else: we don't care (not even about ELF libraries).

Signed-off-by "Yann E. MORIN" <[email protected]>

Cc Arnout Vandecappelle <[email protected]>

---
 support/scripts/check-host-rpath | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

support/scripts/check-host-rpath +9 -4

index 74a25ba99c..169628decb 100755
@@ -18,6 +18,7 @@ main() {
 
     ret=0
     while read file; do
+        is_elf "${file}" || continue
         elf_needs_rpath "${file}" "${hostdir}" || continue
         check_elf_has_rpath "${file}" "${hostdir}" && continue
         if [ ${ret} -eq 0 ]; then

@@ -26,14 +27,18 @@ main() {
             printf "*** ERROR: package %s installs executables without proper RPATH:\n" "${pkg}"
         fi
         printf "***   %s\n" "${file}"
-    done < <( find "${hostdir}"/{bin,sbin} -type f -exec file {} + 2>/dev/null \
-              |sed -r -e '/^([^:]+):.*\<ELF\>.*\<executable\>.*/!d'                \
-                      -e 's//\1/'                                                  \
-            )
+    done < <( find "${hostdir}"/{bin,sbin} -type f 2>/dev/null )
 
     return ${ret}
 }
 
+is_elf() {
+    local f="${1}"
+
+    readelf -l "${f}" 2>/dev/null \
+    |grep -E 'Requesting program interpreter:' >/dev/null 2>&1
+}
+
 elf_needs_rpath() {
     local file="${1}"
     local hostdir="${2}"

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"Yann" == Yann E MORIN <[email protected]> writes:

We sanity-check the host executables that they have a correct RPATH pointing to the host libraries.

This is currently done by looking for all files in $(HOST_DIR) that match the 'ELF executable' pattern (a bit more complex, but that's idea).

However, when an executable is built with -fPIE of -fpie, it no longer appears to be an 'ELF executable', but it rather looks like an 'ELF sheard object' (like if it were an library.

So, we miss those files.

It turns out that the problem is a real one, because quite a few mainline distros, expecially those based on Debian for example, have already switched to generating PIE code by default, and thus we miss on a whole class of systems..

We fix that by simply looking if we can find an ELF interpreter in each file. If we there is one, this is an ELF executable; if not, it may be anything else: we don't care (not even about ELF libraries).

Signed-off-by "Yann E. MORIN" <[email protected]>

Cc Arnout Vandecappelle <[email protected]>