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

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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>
This commit is contained in:
Alex Bennée 2020-06-05 16:49:19 +01:00
parent 4e62bfa9ee
commit 2e886a242c
1 changed files with 7 additions and 1 deletions
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8
exec.c
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@ -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);
}
tlb_flush_page(cpu, addr);
in_page = -(addr | TARGET_PAGE_MASK);
if (len <= in_page) {
tlb_flush_page(cpu, addr);
} else {
tlb_flush(cpu);
}
if (watchpoint)
*watchpoint = wp;