On Mon, Sep 16, 2024 at 02:49:46PM +0100, Alan Maguire wrote:
> use pahole to encode BTF and pfunct to check that
>
> - DWARF functions that made it into BTF match signatures
> - for functions we say we skipped, we did indeed skip them in BTF
> encoding; and
> - it was correct to skip these functions
>
> It is not possible to check everything, as pfunct does not
> print "."-suffixed optimized representations, and it does not
> analyze location calling conventions. As a starting point we check
> for
>
> - functions encoded in BTF match signatures with DWARF
> - functions with multiple incompatible return values
> - functions with incompatible parameter count/type
>
> This test automates manual validation of encoding/skipping,
> and as such will be useful to ensure regressions are not
> introduced, for comparing gcc/LLVM-based DWARF representations
> etc.
>
> The test takes ~5 minutes to run in all; output looks like this:
>
> $ vmlinux=~/kbuild/bpf-next/vmlinux bash ./btf_functions.sh
I'm trying without specifying vmlinux, what we have now in the
tests/tests should find the one for the running kernel and use it, but
doing so I got tons of warnings about egrep usage, so I folded this:
diff --git a/tests/btf_functions.sh b/tests/btf_functions.sh
index 45094077809c1e3e..4a60a18845115d3d 100755
--- a/tests/btf_functions.sh
+++ b/tests/btf_functions.sh
@@ -69,7 +69,7 @@ const_insensitive=0
for f in $funcs ; do
btf=$(grep " $f(" $outdir/btf.funcs)
# look for non-inline match first
- dwarf=$(grep " $f(" $outdir/dwarf.funcs |egrep -v "^inline ")
+ dwarf=$(grep " $f(" $outdir/dwarf.funcs | grep -Ev "^inline ")
if [[ "$btf" != "$dwarf" ]]; then
# function might be declared inline in DWARF.
inline_dwarf=$(grep " $f(" $outdir/dwarf.funcs |grep "^inline ")
Running with it now:
root@x1:/home/acme/git/pahole# tests/tests
1: Validation of BTF encoding of functions; this may take some time...
Seems stuck, so:
root@x1:/home/acme/git/pahole# pahole --running_kernel_vmlinux
/usr/lib/debug/lib/modules/6.10.8-200.fc40.x86_64/vmlinux
root@x1:/home/acme/git/pahole#
Had to stop (traveling/LPC participation), so sending it now, what is
written above should already be useful :)
- Arnaldo
> Validation of BTF encoding of functions; this may take some time...
> Matched 55969 functions exactly.
> Matched 239 functions with inlines.
> Matched 1 functions with multiple const/non-const instances.
> Ok
> Validation of skipped function logic...
> Validating skipped functions are absent from BTF...
> Skipped encoding 748 functions in BTF.
> Ok
> Validating skipped functions have incompatible return values...
> Found 8 functions with multiple incompatible return values.
> Ok
> Validating skipped functions have incompatible params/counts...
> Found 116 instances with multiple instances with incompatible parameters.
> Found 2 instances where inline functions were not inlined and had incompatible parameters.
> Found 351 instances where the function name suggests optimizations led to inconsistent parameters.
> Ok
>
> Suggested-by: Jiri Olsa <olsajiri@xxxxxxxxx>
> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> ---
> tests/btf_functions.sh | 192 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 192 insertions(+)
> create mode 100755 tests/btf_functions.sh
>
> diff --git a/tests/btf_functions.sh b/tests/btf_functions.sh
> new file mode 100755
> index 0000000..4509407
> --- /dev/null
> +++ b/tests/btf_functions.sh
> @@ -0,0 +1,192 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Copyright (c) 2024, Oracle and/or its affiliates.
> +#
> +# Examine functions - especially those for which we skipped BTF encoding -
> +# to validate that they were indeed skipped for BTF encoding, and that they
> +# also should have been.
> +#
> +
> +outdir=
> +
> +fail()
> +{
> + # Do not remove test dir; might be useful for analysis
> + trap - EXIT
> + if [[ -d "$outdir" ]]; then
> + echo "Test data is in $outdir"
> + fi
> + exit 1
> +}
> +
> +cleanup()
> +{
> + rm ${outdir}/*
> + rmdir $outdir
> +}
> +
> +vmlinux=${vmlinux:-$1}
> +
> +if [ -z "$vmlinux" ] ; then
> + vmlinux=$(pahole --running_kernel_vmlinux)
> + if [ -z "$vmlinux" ] ; then
> + echo "Please specify a vmlinux file to operate on"
> + exit 1
> + fi
> +fi
> +
> +if [ ! -f "$vmlinux" ] ; then
> + echo "$vmlinux file not available, please specify another"
> + exit 1
> +fi
> +
> +outdir=$(mktemp -d /tmp/btf_functions.sh.XXXXXX)
> +
> +trap cleanup EXIT
> +
> +test -n "$VERBOSE" && printf "Encoding..."
> +
> +pahole --btf_features=default --btf_encode_detached=$outdir/vmlinux.btf --verbose $vmlinux |grep "skipping BTF encoding of function" > ${outdir}/skipped_fns
> +
> +test -n "$VERBOSE" && printf "done.\n"
> +
> +echo "Validation of BTF encoding of functions; this may take some time..."
> +
> +funcs=$(pfunct --format_path=btf $outdir/vmlinux.btf |sort)
> +
> +# all functions from DWARF; some inline functions are not inlined so include them too
> +pfunct --all --no_parm_names --format_path=dwarf $vmlinux | \
> + awk '{ print $0}'|sort|uniq > $outdir/dwarf.funcs
> +# all functions from BTF (removing bpf_kfunc prefix where found)
> +pfunct --all --no_parm_names --format_path=btf $outdir/vmlinux.btf |\
> + awk '{ gsub("^bpf_kfunc ",""); print $0}'|sort|uniq > $outdir/btf.funcs
> +
> +exact=0
> +inline=0
> +const_insensitive=0
> +
> +for f in $funcs ; do
> + btf=$(grep " $f(" $outdir/btf.funcs)
> + # look for non-inline match first
> + dwarf=$(grep " $f(" $outdir/dwarf.funcs |egrep -v "^inline ")
> + if [[ "$btf" != "$dwarf" ]]; then
> + # function might be declared inline in DWARF.
> + inline_dwarf=$(grep " $f(" $outdir/dwarf.funcs |grep "^inline ")
> + if [[ "inline $btf" != "$inline_dwarf" ]]; then
> + # some functions have multiple instances in DWARF where one has
> + # const param(s) and another does not (see errpos()). We do not
> + # mark these functions inconsistent as though they technically
> + # have different prototypes, the data itself is not different.
> + btf_noconst=$(echo $btf | awk '{gsub("const ",""); print $0 }')
> + dwarf_noconst=$(echo $dwarf | awk '{gsub("const ",""); print $0 }')
> + if [[ "$dwarf_noconst" =~ "$btf_noconst" ]]; then
> + const_insensitive=$((const_insensitive+1))
> + else
> + echo "ERROR: mismatch for '$f()' : BTF '$btf' not found; DWARF '$dwarf'"
> + fail
> + fi
> + else
> + inline=$((inline+1))
> + fi
> + else
> + exact=$((exact+1))
> + fi
> +done
> +
> +echo "Matched $exact functions exactly."
> +echo "Matched $inline functions with inlines."
> +echo "Matched $const_insensitive functions with multiple const/non-const instances."
> +echo "Ok"
> +
> +echo "Validation of skipped function logic..."
> +
> +skipped_cnt=$(wc -l ${outdir}/skipped_fns | awk '{ print $1}')
> +
> +if [[ "$skipped_cnt" == "0" ]]; then
> + echo "No skipped functions. Done."
> + exit 0
> +fi
> +
> +echo "Validating skipped functions are absent from BTF..."
> +
> +skipped_fns=$(awk '{print $1}' $outdir/skipped_fns)
> +for s in $skipped_fns ; do
> + # Ensure the skipped function are not in BTF
> + inbtf=$(grep " $s(" $outdir/btf.funcs)
> + if [[ -n "$inbtf" ]]; then
> + echo "ERROR: '${s}()' was added incorrectly to BTF: '$inbtf'"
> + fail
> + fi
> +done
> +
> +echo "Skipped encoding $skipped_cnt functions in BTF."
> +echo "Ok"
> +
> +echo "Validating skipped functions have incompatible return values..."
> +
> +return_mismatches=$(awk '/return type mismatch/ { print $1 }' $outdir/skipped_fns)
> +return_count=0
> +
> +for r in $return_mismatches ; do
> + # Ensure there are multiple instances with incompatible return values
> + grep " $r(" $outdir/dwarf.funcs | \
> + awk -v FN=$r '{i = index($0, FN); if (i>0) print substr($0, 0, i-1) }' \
> + | uniq > ${outdir}/retvals.$r
> + test -n "$VERBOSE" && echo "'${r}()' has return values:"
> + test -n "$VERBOSE" && cat ${outdir}/retvals.$r
> + cnt=$(wc -l ${outdir}/retvals.$r | awk '{ print $1 }')
> + if [[ $cnt -lt 2 ]]; then
> + echo "ERROR: '${r}()' has only one return value; it should not be reported as having incompatible return values"
> + fail
> + fi
> + return_count=$((return_count+1))
> +done
> +
> +echo "Found $return_count functions with multiple incompatible return values."
> +echo "Ok"
> +
> +echo "Validating skipped functions have incompatible params/counts..."
> +
> +param_mismatches=$(awk '/due to param / { print $1 }' $outdir/skipped_fns)
> +
> +multiple=0
> +multiple_inline=0
> +optimized=0
> +warnings=0
> +
> +for p in $param_mismatches ; do
> + skipmsg=$(awk -v FN=$p '{ if ($1 == FN) print $0 }' $outdir/skipped_fns)
> + altname=$(echo $skipmsg | awk '{ i=index($2,")"); print substr($2,2,i-2); }')
> + if [[ "$altname" != "$p" ]]; then
> + test -n "$VERBOSE" && echo "skipping optimized function $p ($altname); pfunct may not reflect late optimizations."
> + optimized=$((optimized+1))
> + continue
> + fi
> + # Ensure there are multiple instances with incompatible params
> + grep " $p(" $outdir/dwarf.funcs | uniq > ${outdir}/protos.$p
> + test -n "$VERBOSE" && echo "'${p}()' has prototypes:"
> + test -n "$VERBOSE" && cat ${outdir}/protos.$p
> + cnt=$(wc -l ${outdir}/protos.$p | awk '{ print $1 }')
> + if [[ $cnt -lt 2 ]]; then
> + # function may be inlined in multiple sites with different protos
> + inlined=$(grep inline ${outdir}/protos.$p)
> + if [[ -n "$inlined" ]]; then
> + multiple_inline=$((multiple_inline+1))
> + else
> + echo "WARN: '${p}()' has only one prototype; if it was subject to late optimization, pfunct may not reflect inconsistencies pahole found."
> + echo "Full skip message from pahole: $skipmsg"
> + warnings=$((warnings+1))
> + fi
> + else
> + multiple=$((multiple+1))
> + fi
> +done
> +
> +echo "Found $multiple instances with multiple instances with incompatible parameters."
> +echo "Found $multiple_inline instances where inline functions were not inlined and had incompatible parameters."
> +echo "Found $optimized instances where the function name suggests optimizations led to inconsistent parameters."
> +echo "Found $warnings instances where pfunct did not notice inconsistencies."
> +echo "Ok"
> +
> +exit 0
> --
> 2.43.5
