On 30/11/2024 1:10 am, Volodymyr Babchuk wrote:
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index 90268d9249..64fd04f805 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -213,6 +216,20 @@ config SPECULATIVE_HARDEN_LOCK
>
> endmenu
>
> +menu "Compiler options"
> +
> +config STACK_PROTECTOR
> + bool "Stack protection"
Call this "Stack Protector". There is no point deviating from the name
most people know.
> + depends on HAS_STACK_PROTECTOR
> + help
> + Use compiler's option -fstack-protector (supported both by GCC
> + and Clang) to generate code that checks for corrupted stack
> + and halts the system in case of any problems.
> +
> + Please note that this option will impair performance.
This final sentence isn't interesting. All hardening options come with
a cost, and stack protector is small compared to some we have in Xen.
Furthermore, the audience you need to write for is the curious power
user, not a developer.
How about this:
"Enable the Stack Protector compiler hardening option. This inserts a
canary value in the stack frame of functions, and performs an integrity
check on exit."
> diff --git a/xen/common/stack-protector.c b/xen/common/stack-protector.c
> new file mode 100644
> index 0000000000..b258590d3a
> --- /dev/null
> +++ b/xen/common/stack-protector.c
> @@ -0,0 +1,10 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <xen/lib.h>
> +#include <xen/random.h>
> +
> +unsigned long __ro_after_init __stack_chk_guard;
> +
> +void __stack_chk_fail(void)
asmlinkage. This MISRA check is now blocking in Eclair.
> +{
> + panic("Detected stack corruption\n");
At a bare minimum, "Stack Protector integrity violation identified in
%ps\n", __builtin_return_address(0)
It's a little awkward because ending up here means a sibling call from
the same function ended up corrupting the stack, but there's no way of
tracking down which.
> +}
> diff --git a/xen/include/xen/stack-protector.h
> b/xen/include/xen/stack-protector.h
> new file mode 100644
> index 0000000000..779d7cf9ec
> --- /dev/null
> +++ b/xen/include/xen/stack-protector.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef XEN__STACK_PROTECTOR_H
> +#define XEN__STACK_PROTECTOR_H
> +
> +#ifdef CONFIG_STACKPROTECTOR
This is the header needing to include random.h, or it won't compile in
isolation.
~Andrew
