Re: [PATCH] riscv: Disable STACKPROTECTOR_PER_TASK if GCC_PLUGIN_RANDSTRUCT is enabled

From: Guenter Roeck
Date: Wed Aug 04 2021 - 01:25:37 EST


On 8/3/21 10:14 PM, Palmer Dabbelt wrote:
On Fri, 23 Jul 2021 17:58:13 PDT (-0700), Palmer Dabbelt wrote:
On Tue, 06 Jul 2021 09:26:21 PDT (-0700), linux@xxxxxxxxxxxx wrote:
riscv uses the value of TSK_STACK_CANARY to set
stack-protector-guard-offset. With GCC_PLUGIN_RANDSTRUCT enabled, that
value is non-deterministic, and with riscv:allmodconfig often results
in build errors such as

cc1: error: '8120' is not a valid offset in '-mstack-protector-guard-offset='

Enable STACKPROTECTOR_PER_TASK only if GCC_PLUGIN_RANDSTRUCT is disabled
to fix the problem.

Fixes: fea2fed201ee5 ("riscv: Enable per-task stack canaries")
Cc: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
 arch/riscv/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 469a70bd8da6..3afb84fa2190 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -486,6 +486,7 @@ config CC_HAVE_STACKPROTECTOR_TLS

 config STACKPROTECTOR_PER_TASK
     def_bool y
+    depends on !GCC_PLUGIN_RANDSTRUCT
     depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS

 config PHYS_RAM_BASE_FIXED

Thanks, this is on fixes.  I do an allmodconfig build and haven't seen
these failures, is there something special I need to do to get this
working?  I know nothing about GCC plugins...

Sorry, looks like I screwed something up and I didn't actually merge this onto fixes.  Not sure what happened, but this time it should actually be on fixes.

Ah, I thought you decided not to apply it for some reason. I changed
my test scripts to always disable GCC_PLUGIN_RANDSTRUCT for riscv
build tests and stopped reporting the problem. I mentioned this
a couple of weeks ago in my test reports. Just in case you wondered.

Guenter