[Buildroot] [git commit branch/2020.02.x] boot/arm-trusted-firmware: Forward stack protection configuration

Peter Korsgaard peter at korsgaard.com
Mon Dec 21 14:16:12 UTC 2020


commit: https://git.buildroot.net/buildroot/commit/?id=1ed3998ba314c4e7592d2c8c4e8e6a834ee2c237
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2020.02.x

TF-A supports stack smashing protection (-fstack-protector-*).
However, that feature is currently silently disabled because
ENABLE_STACK_PROTECTOR is not set during build time.

As documented in the TF-A user guide, the flag ENABLE_STACK_PROTECTOR
is required to enable stack protection support. When enabled the symbols
for the stack protector (e.g. __stack_chk_guard) are built.
This needs to be done because TF-A does not link against an external
library that provides that symbols (e.g. libc).

So in case we see that BR2_SSP_* is enabled, let's enable the corresponding
ENABLE_STACK_PROTECTOR build flag for TF-A as documented in the TF-A user guide.

This patch also fixes a the following linker errors with older TF-A versions
if BR2_SSP_* is enabled (i.e. -fstack-protector-* is used as compiler flag)
and ENABLE_STACK_PROTECTOR is not set, which are caused by the missing
stack protector symbols:

  [...]
  params_setup.c:(.text.params_early_setup+0xc): undefined reference to `__stack_chk_guard'
  aarch64-none-linux-gnu-ld: params_setup.c:(.text.params_early_setup+0x14): undefined reference to `__stack_chk_guard'
  aarch64-none-linux-gnu-ld: params_setup.c:(.text.params_early_setup+0x104): undefined reference to `__stack_chk_guard'
  aarch64-none-linux-gnu-ld: params_setup.c:(.text.params_early_setup+0x118): undefined reference to `__stack_chk_fail'
  aarch64-none-linux-gnu-ld: ./build/px30/release/bl31/pmu.o: in function `rockchip_soc_sys_pwr_dm_suspend':
  pmu.c:(.text.rockchip_soc_sys_pwr_dm_suspend+0xc): undefined reference to `__stack_chk_guard'
  [...]

TF-A releases after Nov 2019, that include 7af195e29a4, will circumvent
these issue by explicitliy and silently disabling the stack protector
by appending '-fno-stack-protector' to the compiler flags in case
ENABLE_STACK_PROTECTOR is not set.

Tested on a Rockchip PX30 based system (TF-A v2.2 and upstream/master).

Signed-off-by: Christoph Müllner <christoph.muellner at theobroma-systems.com>
Reviewed-by: Baruch Siach <baruch at tkos.co.il>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
(cherry picked from commit 7b3fcbcdaa8cb6a99208399d1402c837685d7639)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 boot/arm-trusted-firmware/arm-trusted-firmware.mk | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/boot/arm-trusted-firmware/arm-trusted-firmware.mk b/boot/arm-trusted-firmware/arm-trusted-firmware.mk
index 37efe82630..72f4404302 100644
--- a/boot/arm-trusted-firmware/arm-trusted-firmware.mk
+++ b/boot/arm-trusted-firmware/arm-trusted-firmware.mk
@@ -96,6 +96,14 @@ ARM_TRUSTED_FIRMWARE_MAKE_OPTS += MV_DDR_PATH=$(MV_DDR_MARVELL_DIR)
 ARM_TRUSTED_FIRMWARE_DEPENDENCIES += mv-ddr-marvell
 endif
 
+ifeq ($(BR2_SSP_REGULAR),y)
+ARM_TRUSTED_FIRMWARE_MAKE_OPTS += ENABLE_STACK_PROTECTOR=default
+else ifeq ($(BR2_SSP_STRONG),y)
+ARM_TRUSTED_FIRMWARE_MAKE_OPTS += ENABLE_STACK_PROTECTOR=strong
+else ifeq ($(BR2_SSP_ALL),y)
+ARM_TRUSTED_FIRMWARE_MAKE_OPTS += ENABLE_STACK_PROTECTOR=all
+endif
+
 ARM_TRUSTED_FIRMWARE_MAKE_TARGETS = all
 
 ifeq ($(BR2_TARGET_ARM_TRUSTED_FIRMWARE_FIP),y)


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