[patch 2/5] -fstack-protector feature: Add the Kconfig option

[Arjan van de Ven]

Subject: [patch 2/5] Add the Kconfig option for the stackprotector feature
From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>

This patch adds the config options for -fstack-protector.

Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
CC: Andi Kleen <ak@xxxxxxx>

---
 arch/x86_64/Kconfig |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

Index: linux-2.6.18-rc4-stackprot/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.18-rc4-stackprot.orig/arch/x86_64/Kconfig
+++ linux-2.6.18-rc4-stackprot/arch/x86_64/Kconfig
@@ -522,6 +522,30 @@ config SECCOMP
 
 	  If unsure, say Y. Only embedded should say N here.
 
+config CC_STACKPROTECTOR
+	bool "Enable -fstack-protector buffer overflow detection (EXPRIMENTAL)"
+	depends on EXPERIMENTAL
+	help
+         This option turns on the -fstack-protector GCC feature. This
+	  feature puts, at the beginning of critical 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, or a distribution
+	  gcc with the feature backported. Older versions are automatically
+	  detected and for those versions, this configuration option is ignored.
+
+config CC_STACKPROTECTOR_ALL
+	bool "Use stack-protector for all functions"
+	depends on CC_STACKPROTECTOR
+	help
+	  Normally, GCC only inserts the canary value protection for
+	  functions that use large-ish on-stack buffers. By enabling
+	  this option, GCC will be asked to do this for ALL functions.
+
 source kernel/Kconfig.hz
 
 config REORDER

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