In order to support a platform overriding StackCheckLibNull
provided by MdeLibs.dsc.inc, the CUSTOM_STACK_CHECK_LIB macro
is introduced. If this macro is defined, MdeLibs.dsc.inc will
not link StackCheckLibNull and it is expected that the platform
will link the version(s) of StackCheckLib that it requires.
The StackCheckLib README is also updated in this patch to
document the new macro and provide additional information.
Signed-off-by: Oliver Smith-Denny <osde@linux.microsoft.com>
StackCheckLib contains the required functionality for initializing
the stack cookie value, checking the value, and triggering an interrupt
when a mismatch occurs. The stack cookie is a random value placed on the
stack between the stack variables and the return address so that
continuously writing past the stack variables will cause the stack cookie
to be overwritten. Before the function returns, the stack cookie value
will be checked and if there is a mismatch then StackCheckLib handles the
failure.
Because UEFI doesn't use the C runtime libraries provided by MSVC, the
stack check code is written in assembly within this library. GCC and
Clang compilers have built-in support for stack cookie checking, so this
library only handles failures.
Signed-off-by: Oliver Smith-Denny <osde@linux.microsoft.com>
Oliver Smith-Denny
Taylor Beebe