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toolchain: granular choice for stack protector

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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@uplinklabs.net>
[yann.morin.1998@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@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@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@free-electrons.com>
This commit is contained in:
Steven Noonan
2015-12-27 12:07:31 +01:00
committed by Thomas Petazzoni
parent 9ac65b37bd
commit d29c7196bf
3 changed files with 56 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
Config.in
View File

@@ -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