No description
01113bc1c5
GDB step cross kernel helpers only works if the kernel helpers are tail called, which is the case how it is used in glibc. See __aeabi_read_tp in sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S. In __aeabi_read_tp, branch/jump to the kernel helper is the last instruction, and the next instruction address is in LR, which is in caller function. GDB can handle this correctly. For example, glibc function __GI___ctype_init calls __aeabi_read_tp 0xb6e19b30 <__GI___ctype_init+4>: ldr r3, [pc, #80] ; 0xb6e19b34 <__GI___ctype_init+8>: bl 0xb6e0a6e0 <__aeabi_read_tp> 0xb6e19b38 <__GI___ctype_init+12>: ldr r3, [pc, r3] and __aeabi_read_tp calls kernel helper, (gdb) disassemble __aeabi_read_tp 0xb6fef5d0 <+0>: mvn r0, #61440 ; 0xf000 0xb6fef5d4 <+4>: sub pc, r0, #31 once GDB or GDBserver single step instruction on 0xb6fef5d4, LR is 0xb6e19b38, which is right address of next instruction to set breakpoint on. However, if the kernel helpers are not tail-called, the LR is still the address in the caller function of kernel helper's caller, which isn't the right address of next instruction to set breakpoint on. For example, we use kernel helper in main, (gdb) disassemble main .... 0x00008624 <+32>: mov r3, #4064 ; 0xfe0^M 0x00008628 <+36>: movt r3, #65535 ; 0xffff^M 0x0000862c <+40>: blx r3 0x00008630 <+44>: ldr r3, [r11, #-8] kernel helper is called on 0x0000862c and the expected next instruction address is 0x00008630, but the LR now is the return address of main. The problem here is LR may not have the right address because when we single step the instruction, it isn't executed yet, so the LR isn't updated. This patch fix this problem by decoding instruction, if the instruction updates LR (BL and BLX), the next instruction address is PC + INSN_SIZE, otherwise, get the address of next instruction from LR. gdb: 2016-02-12 Yao Qi <yao.qi@linaro.org> * arch/arm-linux.c (arm_linux_get_next_pcs_fixup): Calculate nextpc according to instruction. gdb/testsuite: 2016-02-12 Yao Qi <yao.qi@linaro.org> * gdb.arch/arm-single-step-kernel-helper.c: New. * gdb.arch/arm-single-step-kernel-helper.exp: New. |
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bfd | ||
binutils | ||
config | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
zlib | ||
.cvsignore | ||
.gitattributes | ||
.gitignore | ||
ChangeLog | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
COPYING | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
COPYING3 | ||
COPYING3.LIB | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
lt~obsolete.m4 | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release.sh | ||
symlink-tree | ||
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.