[PATCH cygport 0/2] Avoid misbehaviour with llvm-objdump

[PATCH cygport 0/2] Avoid misbehaviour with llvm-objdump

[Jon Turney]

Jon Turney (2):
  postinst: Never remove an existing .gnu_debuglink
  Don't use llvm-objdump

 lib/pkg_info.cygpart     |  8 --------
 lib/src_postinst.cygpart | 35 +++++++++++++++++++----------------
 2 files changed, 19 insertions(+), 24 deletions(-)

-- 
2.34.1

[PATCH cygport 1/2] postinst: Never remove an existing .gnu_debuglink

[Jon Turney]

Be more careful not to remove an existing .gnu_debuglink, even if we
think this package has no useful debug symbols.

(Some versions of 'llvm-objdump -l' fail to find line number info even
though it's there.  Don't break a package which manages it's own debug
symbols (e.g. cygwin) when that happens.)
---
 lib/src_postinst.cygpart | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/lib/src_postinst.cygpart b/lib/src_postinst.cygpart
index d8bb226..e29b2cb 100644
--- a/lib/src_postinst.cygpart
+++ b/lib/src_postinst.cygpart
@@ -1051,23 +1051,31 @@ __prepstrip() {
 
 			lines=$(${objdump} -d -l "${exe}" 2>/dev/null | sed -ne "s|.*\(/usr/src/debug/${PF}/.*\):[0-9]*$|\1|gp" | sort -u | tee -a ${T}/.dbgsrc.out | wc -l);
 
-			if (( lines == 0 ))
+			# we expect --add-gnu-debuglink to fail if a
+			# .gnu_debuglink section already exists (e.g. binutils,
+			# which uses hardlinks, or cygwin which creates a custom
+			# .dbg file), but leave it alone to make sure we don't
+			# mess it up.
+			if ${objdump} -h "${exe}" | grep -q '\.gnu_deb'
 			then
-				${objcopy} --strip-all "${exe}";
 				continue;
 			fi
 
-			# --add-gnu-debuglink will fail if .gnu_debuglink section
-			# already exists, e.g. binutils, which uses hardlinks,
-			# or cygwin which creates a custom .dbg file
-			if ! ${objdump} -h "${exe}" | grep -q '\.gnu_deb'
+			# only create split debuginfo if it's going to contain
+			# some symbols for which this package has the
+			# corresponding source files
+			if (( lines == 0 ))
 			then
-				dodir "${dbg%/*}";
-				${objcopy} --long-section-names enable --add-gnu-debuglink=/dev/null --only-keep-debug "${exe}" "${D}${dbg}";
-				chmod 0644 "${D}${dbg}";
 				${objcopy} --strip-all "${exe}";
-				${objcopy} --long-section-names enable --add-gnu-debuglink="${D}${dbg}" "${exe}" 2>/dev/null;
+				continue;
 			fi
+
+			dodir "${dbg%/*}";
+			${objcopy} --long-section-names enable --add-gnu-debuglink=/dev/null --only-keep-debug "${exe}" "${D}${dbg}";
+			chmod 0644 "${D}${dbg}";
+			${objcopy} --strip-all "${exe}";
+			${objcopy} --long-section-names enable --add-gnu-debuglink="${D}${dbg}" "${exe}" 2>/dev/null;
+
 		fi
 	done
 }
-- 
2.34.1

Re: [PATCH cygport 1/2] postinst: Never remove an existing .gnu_debuglink

[Corinna Vinschen]

Hi Jon,

On Feb  1 17:25, Jon Turney wrote:
> Be more careful not to remove an existing .gnu_debuglink, even if we
> think this package has no useful debug symbols.
> 
> (Some versions of 'llvm-objdump -l' fail to find line number info even
> though it's there.  Don't break a package which manages it's own debug
> symbols (e.g. cygwin) when that happens.)
> ---
>  lib/src_postinst.cygpart | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/lib/src_postinst.cygpart b/lib/src_postinst.cygpart
> index d8bb226..e29b2cb 100644
> --- a/lib/src_postinst.cygpart
> +++ b/lib/src_postinst.cygpart
> @@ -1051,23 +1051,31 @@ __prepstrip() {
>  
>  			lines=$(${objdump} -d -l "${exe}" 2>/dev/null | sed -ne "s|.*\(/usr/src/debug/${PF}/.*\):[0-9]*$|\1|gp" | sort -u | tee -a ${T}/.dbgsrc.out | wc -l);

Shouldn't lines be computed *after* the new check for .gnu_deb?  After
all, it's still pretty time-consuming and if the .gnu_deb check kicks in
it's never tested...

>  
> -			if (( lines == 0 ))
> +			# we expect --add-gnu-debuglink to fail if a
> +			# .gnu_debuglink section already exists (e.g. binutils,
> +			# which uses hardlinks, or cygwin which creates a custom
> +			# .dbg file), but leave it alone to make sure we don't
> +			# mess it up.
> +			if ${objdump} -h "${exe}" | grep -q '\.gnu_deb'
>  			then
> -				${objcopy} --strip-all "${exe}";
>  				continue;
>  			fi
>  
> -			# --add-gnu-debuglink will fail if .gnu_debuglink section
> -			# already exists, e.g. binutils, which uses hardlinks,
> -			# or cygwin which creates a custom .dbg file
> -			if ! ${objdump} -h "${exe}" | grep -q '\.gnu_deb'
> +			# only create split debuginfo if it's going to contain
> +			# some symbols for which this package has the
> +			# corresponding source files
> +			if (( lines == 0 ))
>  			then
> -				dodir "${dbg%/*}";
> -				${objcopy} --long-section-names enable --add-gnu-debuglink=/dev/null --only-keep-debug "${exe}" "${D}${dbg}";
> -				chmod 0644 "${D}${dbg}";
>  				${objcopy} --strip-all "${exe}";
> -				${objcopy} --long-section-names enable --add-gnu-debuglink="${D}${dbg}" "${exe}" 2>/dev/null;
> +				continue;
>  			fi
> +
> +			dodir "${dbg%/*}";
> +			${objcopy} --long-section-names enable --add-gnu-debuglink=/dev/null --only-keep-debug "${exe}" "${D}${dbg}";
> +			chmod 0644 "${D}${dbg}";
> +			${objcopy} --strip-all "${exe}";
> +			${objcopy} --long-section-names enable --add-gnu-debuglink="${D}${dbg}" "${exe}" 2>/dev/null;
> +
>  		fi
>  	done
>  }
> -- 
> 2.34.1

Re: [PATCH cygport 1/2] postinst: Never remove an existing .gnu_debuglink

[Corinna Vinschen]

On Feb  1 20:33, Jon Turney wrote:
> On 01/02/2022 19:22, Corinna Vinschen wrote:
> > Hi Jon,
> > 
> > On Feb  1 17:25, Jon Turney wrote:
> > > Be more careful not to remove an existing .gnu_debuglink, even if we
> > > think this package has no useful debug symbols.
> > > 
> > > (Some versions of 'llvm-objdump -l' fail to find line number info even
> > > though it's there.  Don't break a package which manages it's own debug
> > > symbols (e.g. cygwin) when that happens.)
> > > ---
> > >   lib/src_postinst.cygpart | 28 ++++++++++++++++++----------
> > >   1 file changed, 18 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/lib/src_postinst.cygpart b/lib/src_postinst.cygpart
> > > index d8bb226..e29b2cb 100644
> > > --- a/lib/src_postinst.cygpart
> > > +++ b/lib/src_postinst.cygpart
> > > @@ -1051,23 +1051,31 @@ __prepstrip() {
> > >   			lines=$(${objdump} -d -l "${exe}" 2>/dev/null | sed -ne "s|.*\(/usr/src/debug/${PF}/.*\):[0-9]*$|\1|gp" | sort -u | tee -a ${T}/.dbgsrc.out | wc -l);
> > 
> > Shouldn't lines be computed *after* the new check for .gnu_deb?  After
> > all, it's still pretty time-consuming and if the .gnu_deb check kicks in
> > it's never tested...
> 
> The objdump invocation has the side effect of creating ${T}/.dbgsrc.out,
> which is later used to determine what source files to put into the debuginfo
> package.

Ah, that explains it☝️

[PATCH cygport 2/2] Don't use llvm-objdump

[Jon Turney]

This partially reverts commit e06359bca705624b9712fd16f4ec9945935fd608
This partially reverts commit 6f788165848084d2fb1597689b31faba7d4c483e

The polynomially bad runtime of 'objdump' (which made 'llvm-objdump' the
only practically usable tool on larger binaries) has been fixed since
[1].  Meanwhile, 'llvm-objdump' now appears to have bugs which interfere
with the correct operation of cygport.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=18025#c16
---
 lib/pkg_info.cygpart     | 8 --------
 lib/src_postinst.cygpart | 7 +------
 2 files changed, 1 insertion(+), 14 deletions(-)

diff --git a/lib/pkg_info.cygpart b/lib/pkg_info.cygpart
index 4b18993..08ddd69 100644
--- a/lib/pkg_info.cygpart
+++ b/lib/pkg_info.cygpart
@@ -95,14 +95,6 @@ __list_deps() {
 		dlltool="${CTARGET}-dlltool"
 	fi
 
-	case ${CHOST} in
-	i?86-*|x86_64-*)
-		if check_prog llvm-objdump
-		then
-			objdump="llvm-objdump"
-		fi ;;
-	esac
-
 	pushd ${D}
 
 #****v* Information/DEPS_PATH
diff --git a/lib/src_postinst.cygpart b/lib/src_postinst.cygpart
index e29b2cb..4b51325 100644
--- a/lib/src_postinst.cygpart
+++ b/lib/src_postinst.cygpart
@@ -951,12 +951,7 @@ __prepstrip() {
 			continue
 		fi
 
-		if check_prog llvm-objdump && llvm-size "${exe}" &>/dev/null
-		then
-			objdump="llvm-objdump"
-		else
-			objdump=${objcopy/copy/dump}
-		fi
+		objdump=${objcopy/copy/dump}
 
 		# Static libraries should not be fully stripped, but we can
 		# still provide split debuginfo if desired
-- 
2.34.1