[Buildroot] [git commit] toolchain: granular choice for stack protector
Thomas Petazzoni
thomas.petazzoni at free-electrons.com
Sun Dec 27 14:30:09 UTC 2015
commit: http://git.buildroot.net/buildroot/commit/?id=d29c7196bf5e610123dcc697197d4013d5869f68
branch: http://git.buildroot.net/buildroot/commit/?id=refs/heads/master
Currently, we only support two levels of stach-smashing protection:
- entirely disabled,
- protect _all_ functions with -fstack-protector-all.
-fstack-protector-all tends to be far too aggressive and impacts
performance too much to be worth on a real product.
Add a choice that allows us to select between different levels of
stack-smashing protection:
- none
- basic (NEW)
- strong (NEW)
- all
The differences are documented in the GCC online documentation:
https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Optimize-Options.html
Signed-off-by: Steven Noonan <steven at uplinklabs.net>
[yann.morin.1998 at free.fr:
- rebase
- add legacy handling
- SSP-strong depends on gcc >= 4.9
- slightly simple ifeq-block in package/Makefile.in
- keep the comment in the choice; add a comment shen strong is not
available
- drop the defaults (only keep the legacy)
- update commit log
]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
[Thomas:
- only show the choice if the toolchain has SSP support
- add details for the BR2_SSP_ALL option that it has a significant
performance impact.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
---
Config.in | 45 +++++++++++++++++++++++++++++++++++++++++----
Config.in.legacy | 8 ++++++++
package/Makefile.in | 8 +++++++-
3 files changed, 56 insertions(+), 5 deletions(-)
diff --git a/Config.in b/Config.in
index 0be44d9..9513cc1 100644
--- a/Config.in
+++ b/Config.in
@@ -522,12 +522,13 @@ config BR2_GOOGLE_BREAKPAD_INCLUDE_FILES
endif
-config BR2_ENABLE_SSP
+choice
bool "build code with Stack Smashing Protection"
+ default BR2_SSP_ALL if BR2_ENABLE_SSP # legacy
depends on BR2_TOOLCHAIN_HAS_SSP
help
- Enable stack smashing protection support using GCCs
- -fstack-protector-all option.
+ Enable stack smashing protection support using GCC's
+ -fstack-protector option family.
See http://www.linuxfromscratch.org/hints/downloads/files/ssp.txt
for details.
@@ -536,7 +537,43 @@ config BR2_ENABLE_SSP
support. This is always the case for glibc and eglibc
toolchain, but is optional in uClibc toolchains.
-comment "enabling Stack Smashing Protection requires support in the toolchain"
+config BR2_SSP_NONE
+ bool "None"
+ help
+ Disable stack-smashing protection.
+
+config BR2_SSP_REGULAR
+ bool "-fstack-protector"
+ help
+ Emit extra code to check for buffer overflows, such as stack
+ smashing attacks. This is done by adding a guard variable to
+ functions with vulnerable objects. This includes functions
+ that call alloca, and functions with buffers larger than 8
+ bytes. The guards are initialized when a function is entered
+ and then checked when the function exits. If a guard check
+ fails, an error message is printed and the program exits.
+
+config BR2_SSP_STRONG
+ bool "-fstack-protector-strong"
+ depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9
+ help
+ Like -fstack-protector but includes additional functions to be
+ protected - those that have local array definitions, or have
+ references to local frame addresses.
+
+comment "Stack Smashing Protection strong needs a toolchain w/ gcc >= 4.9"
+ depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_9
+
+config BR2_SSP_ALL
+ bool "-fstack-protector-all"
+ help
+ Like -fstack-protector except that all functions are
+ protected. This option might have a significant performance
+ impact on the compiled binaries.
+
+endchoice
+
+comment "Stack Smashing Protection needs a toolchain w/ SSP"
depends on !BR2_TOOLCHAIN_HAS_SSP
choice
diff --git a/Config.in.legacy b/Config.in.legacy
index 2628796..5d45d04 100644
--- a/Config.in.legacy
+++ b/Config.in.legacy
@@ -145,6 +145,14 @@ endif
###############################################################################
comment "Legacy options removed in 2016.02"
+# BR2_ENABLE_SSP is still referenced in Config.in (default in choice)
+config BR2_ENABLE_SSP
+ bool "Stack Smashing protection now has different levels"
+ help
+ The protection offered by SSP can now be selected from different
+ protection levels. Be sure to review the SSP level in the build
+ options menu.
+
config BR2_PACKAGE_DIRECTFB_CLE266
bool "cle266 driver for directfb removed"
select BR2_LEGACY
diff --git a/package/Makefile.in b/package/Makefile.in
index 82a66c2..c5652af 100644
--- a/package/Makefile.in
+++ b/package/Makefile.in
@@ -159,7 +159,13 @@ TARGET_CFLAGS += -msep-data
TARGET_CXXFLAGS += -msep-data
endif
-ifeq ($(BR2_ENABLE_SSP),y)
+ifeq ($(BR2_SSP_REGULAR),y)
+TARGET_CFLAGS += -fstack-protector
+TARGET_CXXFLAGS += -fstack-protector
+else ifeq ($(BR2_SSP_STRONG),y)
+TARGET_CFLAGS += -fstack-protector-strong
+TARGET_CXXFLAGS += -fstack-protector-strong
+else ifeq ($(BR2_SSP_ALL),y)
TARGET_CFLAGS += -fstack-protector-all
TARGET_CXXFLAGS += -fstack-protector-all
endif
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