Messages in this thread | ![/](/images/icornerl.gif) | | From | Sami Tolvanen <> | Date | Thu, 25 Mar 2021 16:27:51 -0700 | Subject | Re: [PATCH v3 12/17] arm64: implement __va_function |
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On Thu, Mar 25, 2021 at 3:38 AM Mark Rutland <mark.rutland@arm.com> wrote: > > On Tue, Mar 23, 2021 at 01:39:41PM -0700, Sami Tolvanen wrote: > > With CONFIG_CFI_CLANG, the compiler replaces function addresses in > > instrumented C code with jump table addresses. This change implements > > the __va_function() macro, which returns the actual function address > > instead. > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > Is there really no attribute or builtin that can be used to do this > without assembly?
I don't think the compiler currently offers anything that could help us here. Peter, can you think of another way to avoid the function address to jump table address conversion with -fno-sanitize-cfi-canonical-jump-tables?
> IIUC from other patches the symbol tables will contain the "real" > non-cfi entry points (unless we explciitly asked to make the jump table > address canonical), so AFAICT here the compiler should have all the > necessary information to generate either the CFI or non-CFI entry point > addresses, even if it doesn't expose an interface for that today. > > It'd be a lot nicer if we could get the compiler to do this for us.
I agree, that would be quite useful in the kernel.
Sami
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