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 <christophe.leroy@c-s.fr>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Add task_stack.h to livepatch.h to fix build fails]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 1 insertions, 78 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 531e9ef153c0..85c48911938a 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -673,24 +673,9 @@ void do_IRQ(struct pt_regs *regs)
 		set_irq_regs(old_regs);
 		return;
 	}
-
-	/* Prepare the thread_info in the irq stack */
-	irqtp->task = curtp->task;
-	irqtp->flags = 0;
-
-	/* Copy the preempt_count so that the [soft]irq checks work. */
-	irqtp->preempt_count = curtp->preempt_count;
-
 	/* Switch stack and call */
 	call_do_irq(regs, irqtp);
 
-	/* Restore stack limit */
-	irqtp->task = NULL;
-
-	/* Copy back updates to the thread_info */
-	if (irqtp->flags)
-		set_bits(irqtp->flags, &curtp->flags);
-
 	set_irq_regs(old_regs);
 }
 
@@ -698,85 +683,23 @@ void __init init_IRQ(void)
 {
 	if (ppc_md.init_IRQ)
 		ppc_md.init_IRQ();
-
-	exc_lvl_ctx_init();
-
-	irq_ctx_init();
 }
 
 #if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
 struct thread_info   *critirq_ctx[NR_CPUS] __read_mostly;
 struct thread_info    *dbgirq_ctx[NR_CPUS] __read_mostly;
 struct thread_info *mcheckirq_ctx[NR_CPUS] __read_mostly;
-
-void exc_lvl_ctx_init(void)
-{
-	struct thread_info *tp;
-	int i, cpu_nr;
-
-	for_each_possible_cpu(i) {
-#ifdef CONFIG_PPC64
-		cpu_nr = i;
-#else
-#ifdef CONFIG_SMP
-		cpu_nr = get_hard_smp_processor_id(i);
-#else
-		cpu_nr = 0;
-#endif
-#endif
-
-		tp = critirq_ctx[cpu_nr];
-		tp->cpu = cpu_nr;
-		tp->preempt_count = 0;
-
-#ifdef CONFIG_BOOKE
-		tp = dbgirq_ctx[cpu_nr];
-		tp->cpu = cpu_nr;
-		tp->preempt_count = 0;
-
-		tp = mcheckirq_ctx[cpu_nr];
-		tp->cpu = cpu_nr;
-		tp->preempt_count = HARDIRQ_OFFSET;
-#endif
-	}
-}
 #endif
 
 struct thread_info *softirq_ctx[NR_CPUS] __read_mostly;
 struct thread_info *hardirq_ctx[NR_CPUS] __read_mostly;
 
-void irq_ctx_init(void)
-{
-	struct thread_info *tp;
-	int i;
-
-	for_each_possible_cpu(i) {
-		tp = softirq_ctx[i];
-		tp->cpu = i;
-		klp_init_thread_info(tp);
-
-		tp = hardirq_ctx[i];
-		tp->cpu = i;
-		klp_init_thread_info(tp);
-	}
-}
-
 void do_softirq_own_stack(void)
 {
-	struct thread_info *curtp, *irqtp;
+	struct thread_info *irqtp;
 
-	curtp = current_thread_info();
 	irqtp = softirq_ctx[smp_processor_id()];
-	irqtp->task = curtp->task;
-	irqtp->flags = 0;
 	call_do_softirq(irqtp);
-	irqtp->task = NULL;
-
-	/* Set any flag that may have been set on the
-	 * alternate stack
-	 */
-	if (irqtp->flags)
-		set_bits(irqtp->flags, &curtp->flags);
 }
 
 irq_hw_number_t virq_to_hw(unsigned int virq)