Messages in this thread | | | Date | Thu, 26 Aug 1999 01:41:46 +0200 (MET DST) | From | Mikael Pettersson <> | Subject | Re: Hardware-assisted memory-access breakpoints(watchpoints) on i386 |
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Ilya Tsindlekht wrote:
> GDB (and, consequently, its GUI frontends), doesn't support hardware-based > memory access breakpoints (aka watchpoints) on Intel CPUs. Doing this probably > would require some kernel support (extending ptrace?). Is there any reason why > it isn't done? (or is it already done somewhere?)
Linux does seem to give user-space access to at least some debug-related ia32 features: * ptrace PTRACE_POKEUSR lets a debugger record the information that goes into the debug registers when the process is resumed * the debug-related exceptions (#1 and #3) are mapped to SIGTRAP signals, and the debugger can catch those
I do see two possible problems: * The Intel P6 family has a couple of model-specific registers which carry additional information about some debug exceptions. ptrace() should perhaps be extended to allow a debugger to set up and retrieve these MSRs * I don't know what signal info (if any) Linux passes on to the user-space signal handler; in particular, the signal handler would need the PC of the faulting instruction or the address which triggered a data read/write debug exception.
/Mikael
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