[PATCH] estrip: rework hard link logic in save_elf_debug

GDB loads debug files based on the file name given in the .gnu_debuglink
section, prepended with /usr/lib/debug/${dirname}, where dirname is the
absolute path to the parent directory of the binary being executed.

For each unique inode as input, we need a link to the debug file with
the GNU debuglink as its basename. A link to the debug file should exist
for each directory in which the input inode exists.

The debug link names should be based on the .gnu_debuglink value instead
of the name of the file we are processing as input.

The .gnu_debuglink value is based on the name of the first link
processed for each inode. We save this value as a symlink, and then read
it back as we process subsequent links.

For example, given the following input:

INODE PATH
    1 /usr/bin/git
    1 /usr/libexec/git-core/git-add
    2 /usr/bin/git-shell
    2 /usr/libexec/git-core/git-shell

We generate the following inodes for the debug files:

INODE DEBUGLINK
    3 git.debug
    4 git-shell.debug

We should generate the following links:

INODE PATH
    3 /usr/lib/debug/usr/bin/git.debug
    3 /usr/lib/debug/usr/libexec/git-core/git.debug
    4 /usr/bin/debug/usr/bin/git-shell.debug
    4 /usr/bin/debug/usr/libexec/git-core/git-shell.debug

The previous code would have generated this broken output:

INODE PATH
    3 /usr/lib/debug/usr/bin/git.debug
    3 /usr/lib/debug/usr/libexec/git-core/git-add.debug (*)
    4 /usr/bin/debug/usr/bin/git-shell.debug
    4 /usr/bin/debug/usr/libexec/git-core/git-shell.debug

(*) This link has the wrong name.

Bug: https://bugs.gentoo.org/820107
Signed-off-by: Mike Gilbert <[email protected]>
---
 bin/estrip | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/bin/estrip b/bin/estrip
index abe523fff..8134020fd 100755
--- a/bin/estrip
+++ b/bin/estrip
@@ -201,17 +201,29 @@ save_elf_debug() {
 	local x=$1
 	local inode_debug=$2
 	local splitdebug=$3
-	local d_noslash=${D%/}
-	local y=${ED%/}/usr/lib/debug/${x:${#d_noslash}}.debug
+
+	local x_basename=${x##*/}
+	local x_dirname=${x%/*}
+	local y_dirname=${ED%/}/usr/lib/debug/${x_dirname#${D%/}/}
+	local y_basename y
 
 	# dont save debug info twice
 	[[ ${x} == *".debug" ]] && return 0
 
-	mkdir -p "${y%/*}"
+	mkdir -p "${y_dirname}" || die
+
+	if [[ -L ${inode_debug} ]] ; then
+		y_basename=$(readlink "${inode_debug}") || die
+		y_basename=${y_basename##*/}
+		y=${y_dirname}/${y_basename}
 
-	if [ -f "${inode_debug}" ] ; then
-		ln "${inode_debug}" "${y}" || die "ln failed unexpectedly"
+		if [[ ! -e ${y} ]]; then
+			ln -L "${inode_debug}" "${y}" || die
+		fi
 	else
+		y_basename=${x_basename}.debug
+		y=${y_dirname}/${y_basename}
+
 		if [[ -n ${splitdebug} ]] ; then
 			mv "${splitdebug}" "${y}"
 		else
@@ -222,11 +234,12 @@ save_elf_debug() {
 		fi
 		# Only do the following if the debug file was
 		# successfully created (see bug #446774).
-		if [ $? -eq 0 ] ; then
+		if [[ $? -eq 0 ]] ; then
 			local args="a-x,o-w"
 			[[ -g ${x} || -u ${x} ]] && args+=",go-r"
 			chmod ${args} "${y}"
-			ln "${y}" "${inode_debug}" || die "ln failed unexpectedly"
+			# symlink so we can read the name back.
+			ln -s "${y}" "${inode_debug}" || die
 		fi
 	fi
 
@@ -239,8 +252,8 @@ save_elf_debug() {
 		local buildid_dir="${ED%/}/usr/lib/debug/.build-id/${buildid:0:2}"
 		local buildid_file="${buildid_dir}/${buildid:2}"
 		mkdir -p "${buildid_dir}"
-		[ -L "${buildid_file}".debug ] || ln -s "../../${x:$((${#d_noslash} + 1))}.debug" "${buildid_file}.debug"
-		[ -L "${buildid_file}" ] || ln -s "/${x:$((${#d_noslash} + 1))}" "${buildid_file}"
+		[[ -L "${buildid_file}".debug ]] || ln -s "../../${x#${D%/}/}.debug" "${buildid_file}.debug"
+		[[ -L "${buildid_file}" ]] || ln -s "../../../../../${x#${D%/}/}" "${buildid_file}"
 	fi
 }
 
-- 
2.33.1