Commit 2e886a24 authored Jun 05, 2020 by Alex Bennée

exec: flush the whole TLB if a watchpoint crosses a page boundary



There is no particular reason why you can't have a watchpoint in TCG
that covers a large chunk of the address space. We could be clever
about it but these cases are pretty rare and we can assume the user
will expect a little performance degradation.

NB: In my testing gdb will silently squash a watchpoint like:

  watch (char[0x7fffffffff]) *0x0

to a 4 byte watchpoint. Practically it will limit the maximum size
based on max-value-size. However given enough of a tweak the sky is
the limit.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200605154929.26910-5-alex.bennee@linaro.org>

parent 4e62bfa9

exec.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -1038,6 +1038,7 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, vaddr len,
		int flags, CPUWatchpoint **watchpoint)
		{
		CPUWatchpoint *wp;
		vaddr in_page;

		/* forbid ranges which are empty or run off the end of the address space */
		if (len == 0 \|\| (addr + len - 1) < addr) {
		@@ -1058,7 +1059,12 @@ int cpu_watchpoint_insert(CPUState *cpu, vaddr addr, vaddr len,
		QTAILQ_INSERT_TAIL(&cpu->watchpoints, wp, entry);
		}

		in_page = -(addr \| TARGET_PAGE_MASK);
		if (len <= in_page) {
		tlb_flush_page(cpu, addr);
		} else {
		tlb_flush(cpu);
		}

		if (watchpoint)
		*watchpoint = wp;