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For the BTS recording format, we sometimes get a FROM->TO record where the FROM address lies in the kernel and the TO address lies in user space at whatever address the user process was resumed. GDB has a heuristic to filter out such records based on looking at the most significant bit in the PC. This works fine for 64-bit systems but it doesn't always work for 32-bit systems. Libraries that are loaded at fairly high addresses might be mistaken for kernel code and branches inside the library are filtered out. Change the heuristic to (again heuristically) try to determine the lowest address in kernel space. Any PC that is smaller than that should be in user space. On today's systems, there should be a symbol "_text" at that address. Read /proc/kallsyms and search for that symbol. It is not guaranteed that /proc/kallsyms is readable on all systems. On 64-bit systems, we fall back to check the most significant bit. On 32-bit systems, we refrain from filtering out addresses. The filtering should really be done by the kernel. And it soon will be: https://lkml.org/lkml/2015/8/31/212. gdb/ * nat/linux-btrace.h (struct btrace_target_info) <ptr_bits>: Remove. * nat/linux-btrace.c: Include filestuff.h and inttypes.h. Remove include of sys/utsname.h. (linux_determine_kernel_ptr_bits): Remove. (linux_determine_kernel_start): New. (perf_event_is_kernel_addr): Remove tinfo argument. Update users. Update check. (perf_event_skip_bts_record): Remove tinfo argument. Update users. (linux_enable_bts, linux_enable_pt): Remove tinfo->ptr_bits initialization. * x86-linux-nat.c (x86_linux_enable_btrace): Remove ptr_bits assignment. gdbserver/ * linux-low.c (linux_low_enable_btrace): Remove. (linux_target_ops): Replace linux_low_enable_btrace with linux_enable_btrace.
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.