diff options
Diffstat (limited to 'etc/DEBUG')
| -rw-r--r-- | etc/DEBUG | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/etc/DEBUG b/etc/DEBUG index 1680aab4385..6c7f4040b8d 100644 --- a/etc/DEBUG +++ b/etc/DEBUG @@ -928,7 +928,10 @@ data that is modified only very rarely.) It is also useful to look at the corrupted object or data structure in a fresh Emacs session and compare its contents with a session that you -are debugging. +are debugging. This might be somewhat harder on modern systems which +randomize addresses of running executables (the so-called Address +Space Layout Randomization, or ASLR, feature). If you have this +problem, see below under "How to disable ASLR". ** Debugging the TTY (non-windowed) version @@ -1080,6 +1083,34 @@ suppresses some Valgrind false alarms during Emacs garbage collection: Unfortunately Valgrind suppression files tend to be system-dependent, so you will need to keep one around that matches your system. +** How to disable ASLR + +Modern systems use the so-called Address Space Layout Randomization, +(ASLR) feature, which randomizes the base address of running programs, +making it harder for malicious software or hackers to find the address +of some function or variable in a running program by looking at its +executable file. This causes the address of the same symbol to be +different across rerunning of the same program. Sometimes, it can be +useful to disable ASLR, for example, if you want to compare objects in +two different Emacs sessions. + +On GNU/Linux, you can disable ASLR temporarily with the following +shell command: + + echo 0 > /proc/sys/kernel/randomize_va_space + +or by running Emacs in an environment where ASLR is temporarily +disabled: + + setarch -R emacs [args...] + +To disable ASLR in Emacs on MS-Windows, you will have to rebuild Emacs +while adding '-Wl,-disable-dynamicbase' to LD_SWITCH_SYSTEM_TEMACS +variable defined in src/Makefile. Alternatively, use some tool to +edit the PE header of the Emacs executable file and reset the +DYNAMIC_BASE (0x40) flag in the DllCharacteristics flags recorded by +the PE header. + ** How to recover buffer contents from an Emacs core dump file The file etc/emacs-buffer.gdb defines a set of GDB commands for |