From 79ced5a893677abf303b3a97290454c1b991b1ae Mon Sep 17 00:00:00 2001 From: "Gabriel F. T. Gomes" Date: Tue, 24 Sep 2019 14:21:42 -0300 Subject: [PATCH] Add helper script for glibc debugging This patch adds a new make rule that generates a helper script for debugging glibc test cases. The new script, debugglibc.sh, is similar to testrun.sh, in the sense that it allows the execution of the specified test case, however, it opens the test case in GDB, setting the library path the same way that testrun.sh does. The commands are based on the instructions on the wiki for glibc debugging [1,2]. By default, the script tells GDB to load the test case for symbol information, so that, when a breakpoint is hit, the call stack is displayed correctly (instead of printing lots of '??'s). For instance, after running 'make' and 'make check', one could do the following: $ ./debugglibc.sh nptl/tst-exec1 -b pthread_join Reading symbols from /home/gabriel/build/powerpc64le/glibc//elf/ld.so...done. Breakpoint 1 at 0x1444 add symbol table from file "nptl/tst-exec1" [Thread debugging using libthread_db enabled] Using host libthread_db library "/home/gabriel/build/powerpc64le/glibc//nptl_db/libthread_db.so.1". Breakpoint 1, 0x00007ffff7fb1444 in _dl_start_user () from /home/gabriel/build/powerpc64le/glibc/elf/ld.so Breakpoint 2 at 0x7ffff7f49d48: file pthread_join.c, line 23. Notice that the script will always start GDB with the program running and halted at _dl_start_user. So, in order to reach the actual breakpoint of interest, one should hit 'c', not 'r': >>> c Continuing. [New Thread 0x7ffff7d1f180 (LWP 76443)] [Switching to Thread 0x7ffff7d1f180 (LWP 76443)] Thread 2 "ld.so" hit Breakpoint 2, __pthread_join (threadid=140737354087616, thread_return=0x0) at pthread_join.c:24 24 return __pthread_timedjoin_ex (threadid, thread_return, NULL, true); Then inspect the call stack with 'bt', as usual, and see symbols from both the test case and from the libraries themselves: >>> bt #0 __pthread_join (threadid=140737354087616, thread_return=0x0) at pthread_join.c:24 #1 0x0000000010001f4c in tf (arg=) at tst-exec1.c:37 #2 0x00007ffff7f487e8 in start_thread (arg=0x7ffff7510000) at pthread_create.c:479 #3 0x00007ffff7e523a8 in clone () at ../sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S:82 Tested for powerpc64le and x86_64. [1] https://sourceware.org/glibc/wiki/Debugging/Loader_Debugging [2] https://sourceware.org/glibc/wiki/Testing/Builds#Required_gdb_setup Reviewed-by: Carlos O'Donell Reviewed-by: Dmitry V. Levin Reviewed-by: Joseph Myers Reviewed-by: Andreas Schwab --- Makefile | 158 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 157 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index 67ddd01bfe2..a50fb64dc24 100644 --- a/Makefile +++ b/Makefile @@ -187,7 +187,163 @@ $(common-objpfx)testrun.sh: $(common-objpfx)config.make \ mv -f $@T $@ postclean-generated += testrun.sh -others: $(common-objpfx)testrun.sh +define debugglibc +#!/bin/bash + +SOURCE_DIR="$(CURDIR)" +BUILD_DIR="$(common-objpfx)" +CMD_FILE="$(common-objpfx)debugglibc.gdb" +DIRECT=true +SYMBOLSFILE=true +unset TESTCASE +unset BREAKPOINTS +unset ENVVARS + +usage() +{ +cat << EOF +Usage: $$0 [OPTIONS] + + where is the path to the program being tested. + +Options: + + -h, --help + Prints this message and leaves. + + The following options require one argument: + + -b, --breakpoint + Breakpoints to set at the beginning of the execution + (each breakpoint demands its own -b option, e.g. -b foo -b bar) + -e, --environment-variable + Environment variables to be set with 'exec-wrapper env' in GDB + (each environment variable demands its own -e option, e.g. + -e FOO=foo -e BAR=bar) + + The following options do not take arguments: + + -i, --no-direct + Selects whether to pass the flag --direct to gdb. + Required for glibc test cases and not allowed for non-glibc tests. + Default behaviour is to pass the flag --direct to gdb. + -s, --no-symbols-file + Do not tell GDB to load debug symbols from the testcase. +EOF +} + +# Parse input options +while [[ $$# > 0 ]] +do + key="$$1" + case $$key in + -h|--help) + usage + exit 0 + ;; + -b|--breakpoint) + BREAKPOINTS="break $$2\n$$BREAKPOINTS" + shift + ;; + -e|--environment-variable) + ENVVARS="$$2 $$ENVVARS" + shift + ;; + -i|--no-direct) + DIRECT=false + ;; + -s|--no-symbols-file) + SYMBOLSFILE=false + ;; + *) + TESTCASE=$$1 + ;; + esac + shift +done + +# Check for required argument +if [ ! -v TESTCASE ] +then + usage + exit 1 +fi + +# Expand environment setup command +if [ -v ENVVARS ] +then + ENVVARSCMD="set exec-wrapper env $$ENVVARS" +fi + +# Expand direct argument +if [ "$$DIRECT" == true ] +then + DIRECT="--direct" +else + DIRECT="" +fi + +# Expand symbols loading command +if [ "$$SYMBOLSFILE" == true ] +then + SYMBOLSFILE="add-symbol-file $${TESTCASE}" +else + SYMBOLSFILE="" +fi + +# GDB commands template +template () +{ +cat < $$CMD_FILE + +echo +echo "Debugging glibc..." +echo "Build directory : $$BUILD_DIR" +echo "Source directory : $$SOURCE_DIR" +echo "GLIBC Testcase : $$TESTCASE" +echo "GDB Commands : $$CMD_FILE" +echo "Env vars : $$ENVVARS" +echo + +# Start the test case debugging in two steps: +# 1. the following command invokes gdb to run the loader; +# 2. the commands file tells the loader to run the test case. +gdb -q \ + -x $${CMD_FILE} \ + -d $${SOURCE_DIR} \ + $${BUILD_DIR}/elf/ld.so +endef + +# This is another handy script for debugging dynamically linked program +# against the current libc build for testing. +$(common-objpfx)debugglibc.sh: $(common-objpfx)config.make \ + $(..)Makeconfig $(..)Makefile + $(file >$@T,$(debugglibc)) + chmod a+x $@T + mv -f $@T $@ +postclean-generated += debugglibc.sh debugglibc.gdb + +others: $(common-objpfx)testrun.sh $(common-objpfx)debugglibc.sh # Makerules creates a file `stubs' in each subdirectory, which # contains `#define __stub_FUNCTION' for each function defined in that -- 2.39.2