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a35606d901
While working on the testsuite, I ended up noticing that GDB fails to produce a full backtrace from a thread waiting in pthread_join. When selecting the waiting thread and using the 'bt' command, the following result can be observed: (gdb) bt #0 0x0000003ff7fccd20 in __futex_abstimed_wait_common64 () from /lib/riscv64-linux-gnu/libpthread.so.0 #1 0x0000003ff7fc43da in __pthread_clockjoin_ex () from /lib/riscv64-linux-gnu/libpthread.so.0 Backtrace stopped: frame did not save the PC On my platform, I do not have debug symbols for glibc, so I need to rely on prologue analysis in order to unwind stack. Here is what the function prologue looks like: (gdb) disassemble __pthread_clockjoin_ex Dump of assembler code for function __pthread_clockjoin_ex: 0x0000003ff7fc42de <+0>: addi sp,sp,-144 0x0000003ff7fc42e0 <+2>: sd s5,88(sp) 0x0000003ff7fc42e2 <+4>: auipc s5,0xd 0x0000003ff7fc42e6 <+8>: ld s5,-2(s5) # 0x3ff7fd12e0 0x0000003ff7fc42ea <+12>: ld a5,0(s5) 0x0000003ff7fc42ee <+16>: sd ra,136(sp) 0x0000003ff7fc42f0 <+18>: sd s0,128(sp) 0x0000003ff7fc42f2 <+20>: sd s1,120(sp) 0x0000003ff7fc42f4 <+22>: sd s2,112(sp) 0x0000003ff7fc42f6 <+24>: sd s3,104(sp) 0x0000003ff7fc42f8 <+26>: sd s4,96(sp) 0x0000003ff7fc42fa <+28>: sd s6,80(sp) 0x0000003ff7fc42fc <+30>: sd s7,72(sp) 0x0000003ff7fc42fe <+32>: sd s8,64(sp) 0x0000003ff7fc4300 <+34>: sd s9,56(sp) 0x0000003ff7fc4302 <+36>: sd a5,40(sp) As far as prologue analysis is concerned, the most interesting part is done at address 0x0000003ff7fc42ee (<+16>): 'sd ra,136(sp)'. This stores the RA (return address) register on the stack, which is the information we are looking for in order to identify the caller. In the current implementation of the prologue scanner, GDB stops when hitting 0x0000003ff7fc42e6 (<+8>) because it does not know what to do with the 'ld' instruction. GDB thinks it reached the end of the prologue but have not yet reached the important part, which explain GDB's inability to unwind past this point. The section of the prologue starting at <+4> until <+12> is used to load the stack canary[1], which will then be placed on the stack at <+36> at the end of the prologue. In order to have the prologue properly handled, this commit proposes to add support for the ld instruction in the RISC-V prologue scanner. I guess riscv32 would use lw in such situation so this patch also adds support for this instruction. With this patch applied, gdb is now able to unwind past pthread_join: (gdb) bt #0 0x0000003ff7fccd20 in __futex_abstimed_wait_common64 () from /lib/riscv64-linux-gnu/libpthread.so.0 #1 0x0000003ff7fc43da in __pthread_clockjoin_ex () from /lib/riscv64-linux-gnu/libpthread.so.0 #2 0x0000002aaaaaa88e in bar() () #3 0x0000002aaaaaa8c4 in foo() () #4 0x0000002aaaaaa8da in main () I have had a look to see if I could reproduce this easily, but in my simple testcases using '-fstack-protector-all', the canary is loaded after the RA register is saved. I do not have a reliable way of generating a prologue similar to the problematic one so I forged one instead. The testsuite have been run on riscv64 ubuntu 21.01 with no regression observed. [1] https://en.wikipedia.org/wiki/Buffer_overflow_protection#Canaries |
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bfd | ||
binutils | ||
config | ||
contrib | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gdbserver | ||
gdbsupport | ||
gnulib | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libctf | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
zlib | ||
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.gitattributes | ||
.gitignore | ||
ar-lib | ||
ChangeLog | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
COPYING | ||
COPYING3 | ||
COPYING3.LIB | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
lt~obsolete.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
multilib.am | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release.sh | ||
symlink-tree | ||
test-driver | ||
ylwrap |
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.