sh: initial stack protector support.

This implements basic -fstack-protector support, based on the early ARM
version in c743f38013aeff58ef6252601e397b5ba281c633. The SMP case is
limited to the initial canary value, while the UP case handles per-task
granularity (limited to 32-bit sh until a new enough sh64 compiler
manifests itself).

Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono@st.com>
Reviewed-by: Carmelo Amoroso <carmelo.amoroso@st.com>
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index ff9e033ce626..60ed3669979d 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -685,6 +685,20 @@ config SECCOMP
 
           If unsure, say N.
 
+config CC_STACKPROTECTOR
+        bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
+        depends on SUPERH32 && EXPERIMENTAL
+        help
+          This option turns on the -fstack-protector GCC feature. This
+          feature puts, at the beginning of functions, a canary value on
+          the stack just before the return address, and validates
+          the value just before actually returning.  Stack based buffer
+          overflows (that need to overwrite this return address) now also
+          overwrite the canary, which gets detected and the attack is then
+          neutralized via a kernel panic.
+
+          This feature requires gcc version 4.2 or above.
+
 config SMP
         bool "Symmetric multi-processing support"
         depends on SYS_SUPPORTS_SMP