From: John Högberg<john.hogberg@ericsson.com>
Unlike architectures with precise self-modifying code semantics
(e.g. x86) ARM processors do not maintain coherency for instruction
execution and memory, and require the explicit use of cache
management instructions as well as an instruction barrier to make
code updates visible (the latter on every core that is going to
execute said code).
While this is required to make JITs work on actual hardware, QEMU
has gotten away with not handling this since it does not emulate
caches, and unconditionally invalidates code whenever the softmmu
or the user-mode page protection logic detects that code has been
modified.
Unfortunately the latter does not work in the face of dual-mapped
code (a common W^X workaround), where one page is executable and
the other is writable: user-mode has no way to connect one with the
other as that is only known to the kernel and the emulated
application.
This commit works around the issue by invalidating code in
IC IVAU instructions.
Resolves:https://gitlab.com/qemu-project/qemu/-/issues/1034
Co-authored-by: Richard Henderson<richard.henderson@linaro.org>
Signed-off-by: John Högberg<john.hogberg@ericsson.com>
---
target/arm/helper.c | 47 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 44 insertions(+), 3 deletions(-)