From ed1cd6deb013a11959d17a94e35ce159197632da Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Thu, 31 Jan 2019 10:08:58 +0000 Subject: powerpc: Activate CONFIG_THREAD_INFO_IN_TASK This patch activates CONFIG_THREAD_INFO_IN_TASK which moves the thread_info into task_struct. Moving thread_info into task_struct has the following advantages: - It protects thread_info from corruption in the case of stack overflows. - Its address is harder to determine if stack addresses are leaked, making a number of attacks more difficult. This has the following consequences: - thread_info is now located at the beginning of task_struct. - The 'cpu' field is now in task_struct, and only exists when CONFIG_SMP is active. - thread_info doesn't have anymore the 'task' field. This patch: - Removes all recopy of thread_info struct when the stack changes. - Changes the CURRENT_THREAD_INFO() macro to point to current. - Selects CONFIG_THREAD_INFO_IN_TASK. - Modifies raw_smp_processor_id() to get ->cpu from current without including linux/sched.h to avoid circular inclusion and without including asm/asm-offsets.h to avoid symbol names duplication between ASM constants and C constants. - Modifies klp_init_thread_info() to take a task_struct pointer argument. Signed-off-by: Christophe Leroy Reviewed-by: Nicholas Piggin [mpe: Add task_stack.h to livepatch.h to fix build fails] Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/smp.h | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/include/asm/smp.h') diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h index 41695745032c..0de717e16dd6 100644 --- a/arch/powerpc/include/asm/smp.h +++ b/arch/powerpc/include/asm/smp.h @@ -83,7 +83,22 @@ int is_cpu_dead(unsigned int cpu); /* 32-bit */ extern int smp_hw_index[]; -#define raw_smp_processor_id() (current_thread_info()->cpu) +/* + * This is particularly ugly: it appears we can't actually get the definition + * of task_struct here, but we need access to the CPU this task is running on. + * Instead of using task_struct we're using _TASK_CPU which is extracted from + * asm-offsets.h by kbuild to get the current processor ID. + * + * This also needs to be safeguarded when building asm-offsets.s because at + * that time _TASK_CPU is not defined yet. It could have been guarded by + * _TASK_CPU itself, but we want the build to fail if _TASK_CPU is missing + * when building something else than asm-offsets.s + */ +#ifdef GENERATING_ASM_OFFSETS +#define raw_smp_processor_id() (0) +#else +#define raw_smp_processor_id() (*(unsigned int *)((void *)current + _TASK_CPU)) +#endif #define hard_smp_processor_id() (smp_hw_index[smp_processor_id()]) static inline int get_hard_smp_processor_id(int cpu) -- cgit v1.2.3