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-rw-r--r--security/Kconfig.hardening19
1 files changed, 19 insertions, 0 deletions
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index a56c36470cb1..023aea5e117c 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -217,6 +217,25 @@ config INIT_ON_FREE_DEFAULT_ON
touching "cold" memory areas. Most cases see 3-5% impact. Some
synthetic workloads have measured as high as 8%.
+config CC_HAS_ZERO_CALL_USED_REGS
+ def_bool $(cc-option,-fzero-call-used-regs=used-gpr)
+
+config ZERO_CALL_USED_REGS
+ bool "Enable register zeroing on function exit"
+ depends on CC_HAS_ZERO_CALL_USED_REGS
+ help
+ At the end of functions, always zero any caller-used register
+ contents. This helps ensure that temporary values are not
+ leaked beyond the function boundary. This means that register
+ contents are less likely to be available for side channels
+ and information exposures. Additionally, this helps reduce the
+ number of useful ROP gadgets by about 20% (and removes compiler
+ generated "write-what-where" gadgets) in the resulting kernel
+ image. This has a less than 1% performance impact on most
+ workloads. Image size growth depends on architecture, and should
+ be evaluated for suitability. For example, x86_64 grows by less
+ than 1%, and arm64 grows by about 5%.
+
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