Messages in this thread | | | Date | Fri, 13 Feb 2009 20:23:01 +0530 | From | "K.Prasad" <> | Subject | [Patch 00/10] Hardware Breakpoint interfaces |
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Hi Ingo, Please find the patches that introduce interfaces to access Hardware Breakpoint (or watchpoint) registers and an arch-specific implementation for x86/x86_64 architecture. The patches have been re-based to -tip tree (commit 4e3bae758b552d6bd094fb36e78a4d738cb42257)
A short description of the framework and interfaces is provided below. Some of the details will be specific to x86/x86_64 architecture and may vary depending upon the support provided by the target processor.
Kindly accept these patches to become a part of -tip tree.
Description ------------- The Hardware Breakpoint registers can be used for tracing changes to a variable or data location (even I/O ports in x86/x86_64) and will be extremely helpful in debugging problems such as memory corruption. While these registers have been used by user-space debuggers for long (through 'ptrace' syscalls), Kgdb exploited them for kernel-space addresses.
The proposed framework, introduces interfaces to use them directly on both user- and kernel-space addresses apart from arbitrating requests from various such users for the limited number of registers.
The interfaces are:
int register_kernel_hw_breakpoint(struct hw_breakpoint *); void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp);
int register_user_hw_breakpoint(struct task_struct *tsk, struct hw_breakpoint *bp); void unregister_user_hw_breakpoint(struct task_struct *tsk, struct hw_breakpoint *bp);
The 'struct hw_breakpoint' will be the anchor data-structure containing all the necessary information such as name or address, type, length, priority and pointers to handler functions (some of which are arch-specific). More information about the role of each field, the handler functions and their return values can be found in the descriptive comments preceding these functions and in "include/asm-generic/hw_breakpoint.h".
While (un)register_user_hw_breakpoint() isn't exported yet, its worker-routine __register_user-hw_breakpoint() is used by ptrace syscall for all breakpoint register requirements. For the kernel-space, a simple use case to trace 'write' operations on a kernel variable can be found in samples/hw_breakpoint/data_breakpoint.c.
In the current patchset, support is provided only for read and read-write breakpoints on data locations, which can be later expand to include instruction and I/O breakpoints for x86/x86_64.
There is pending integration with 'KGDB' without which mutual exclusion between them (KGDB and HW breakpoint use through above interfaces) needs to be observed.
Thanks, K.Prasad
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