mirror of
https://sourceware.org/git/binutils-gdb.git
synced 2024-12-15 04:31:49 +08:00
591a12a1d4
This patch handles another aspect of the ELFv2 ABI, which unfortunately requires common code changes. In ELFv2, functions may provide both a global and a local entry point. The global entry point (where the function symbol points to) is intended to be used for function-pointer or cross-module (PLT) calls, and requires r12 to be set up to the entry point address itself. The local entry point (which is found at a fixed offset after the global entry point, as defined by bits in the symbol table entries' st_other field), instead expects r2 to be set up to the current TOC. Now, when setting a breakpoint on a function by name, you really want that breakpoint to trigger either way, no matter whether the function is called via its local or global entry point. Since the global entry point will always fall through into the local entry point, the way to achieve that is to simply set the breakpoint at the local entry point. One way to do that would be to have prologue parsing skip the code sequence that makes up the global entry point. Unfortunately, this does not work reliably, since -for optimized code- GDB these days will not actuall invoke the prologue parsing code but instead just set the breakpoint at the symbol address and rely on DWARF being correct at any point throughout the function ... Unfortunately, I don't really see any way to express the notion of local entry points with the current set of gdbarch callbacks. Thus this patch adds a new callback, skip_entrypoint, that is somewhat analogous to skip_prologue, but is called every time GDB needs to determine a function start address, even in those cases where GDB decides to not call skip_prologue. As a side effect, the skip_entrypoint implementation on ppc64 does not need to perform any instruction parsing; it can simply rely on the local entry point flags in the symbol table entry. With this implemented, two test cases would still fail to set the breakpoint correctly, but that's because they use the construct: gdb_test "break *hello" Now, using "*hello" explicitly instructs GDB to set the breakpoint at the numerical value of "hello" treated as function pointer, so it will by definition only hit the global entry point. I think this behaviour is unavoidable, but acceptable -- most people do not use this construct, and if they do, they get what they asked for ... In one of those two test cases, use of this construct is really not appropriate. I think this was added way back when as a means to work around prologue skipping problems on some platforms. These days that shouldn't really be necessary any more ... For the other (step-bt), we really want to make sure backtracing works on the very first instruction of the routine. To enable that test also on powerpc64le-linux, we can modify the code to call the test function via function pointer (which makes it use the global entry point in the ELFv2 ABI). gdb/ChangeLog: * gdbarch.sh (skip_entrypoint): New callback. * gdbarch.c, gdbarch.h: Regenerate. * symtab.c (skip_prologue_sal): Call gdbarch_skip_entrypoint. * infrun.c (fill_in_stop_func): Likewise. * ppc-linux-tdep.c: Include "elf/ppc64.h". (ppc_elfv2_elf_make_msymbol_special): New function. (ppc_elfv2_skip_entrypoint): Likewise. (ppc_linux_init_abi): Install them for ELFv2. gdb/testsuite/ChangeLog: * gdb.base/sigbpt.exp: Do not use "*" when setting breakpoint on a function. * gdb.base/step-bt.c: Call hello via function pointer to make sure its first instruction is executed on powerpc64le-linux. |
||
|---|---|---|
| bfd | ||
| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| .cvsignore | ||
| .gitignore | ||
| 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 | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release | ||
| 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.