gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support

We will be enabling THREAD_INFO_IN_TASK support for ARM, which means
that we can no longer load the stack canary value by masking the stack
pointer and taking the copy that lives in thread_info. Instead, we will
be able to load it from the task_struct directly, by using the TPIDRURO
register which will hold the current task pointer when
THREAD_INFO_IN_TASK is in effect. This is much more straight-forward,
and allows us to declutter this code a bit while at it.

Note that this means that ARMv6 (non-v6K) SMP systems can no longer use
this feature, but those are quite rare to begin with, so this is a
reasonable trade off.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>

This commit is contained in:

Ard Biesheuvel

2021-09-18 10:44:34 +02:00

parent 6880fa6c56

commit dfbdcda280

7 changed files with 8 additions and 39 deletions

									
										arch/arm/include/asm/stackprotector.h
									
		-2
	
												View File
												
				@@ -39,8 +39,6 @@ static __always_inline void boot_init_stack_canary(void)

					current->stack_canary = canary;

				#ifndef CONFIG_STACKPROTECTOR_PER_TASK

					__stack_chk_guard = current->stack_canary;

				#else

					current_thread_info()->stack_canary = current->stack_canary;

				#endif

				}