S. P. Prasanna wrote:
Yes, that's simple. but slower, as you have a double jump. Probably
a damned sight faster than int3 though.
M.
The advantage of using int3 over jmp to launch the instrumented
module is that int3 (or breakpoint in most architectures) is an
atomic operation to insert.
Yes, 5 bytes is not an atomic write except on 64-bit. So a race is possible.
How about this workaround:
1. Overwrite the start of the function with a hlt, which is atomic.
2. Write that 5-byte jump after the hlt.
3. Overwrite the hlt with nop so things will work
4. interrupt any cpus that got stuck on the hlt - or just wait for the
timer.
Helge Hafting
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