Re: [PATCH 03/17] mm: add generic __va_function and __pa_function macros

Kees Cook
2021-03-12T02:41:15Z

On Thu, Mar 11, 2021 at 04:49:05PM -0800, Sami Tolvanen wrote:
> With CONFIG_CFI_CLANG, the compiler replaces function addresses
> in instrumented C code with jump table addresses. This means that
> __pa_symbol(function) returns the physical address of the jump table
> entry instead of the actual function, which may not work as the jump
> table code will immediately jump to a virtual address that may not be
> mapped.
>
> To avoid this address space confusion, this change adds generic
> definitions for __va_function and __pa_function, which architectures
> that support CFI can override. The typical implementation of the
> __va_function macro would use inline assembly to take the function
> address, which avoids compiler instrumentation.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

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Kees Cook