On 03/16/2010 10:10 PM, Blue Swirl wrote:
Yes, and is what tlb_protect_code() does and it's called from
tb_alloc_page() which is what's code when a TB is created.
Just a tangential note: a long time ago, I tried to disable self
modifying code detection for Sparc. On most RISC architectures, SMC
needs explicit flushing so in theory we need not track code memory
writes. However, during exceptions the translator needs to access the
original unmodified code that was used to generate the TB. But maybe
there are other ways to avoid SMC tracking, on x86 it's still needed
On x86 you're supposed to execute a serializing instruction (one of
INVD, INVEPT, INVLPG, INVVPID, LGDT, LIDT, LLDT, LTR, MOV (to control
register, with the exception of MOV CR8), MOV (to debug register),
WBINVD, WRMSR, CPUID, IRET, and RSM) before running modified code.
but I suppose SMC is pretty rare.
Every time you demand load a code page from disk, you're running self
modifying code (though it usually doesn't exist in the tlb, so there's
no previous version that can cause trouble).
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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