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>

arch/powerpc/Kconfig

@@ -238,6 +238,7 @@ config PPC
  select RTC_LIB
  select SPARSE_IRQ
  select SYSCTL_EXCEPTION_TRACE
+ select THREAD_INFO_IN_TASK
  select VIRT_TO_BUS if !PPC64
  #
  # Please keep this list sorted alphabetically.

arch/powerpc/Makefile

@@ -427,6 +427,13 @@ else
 endif
 endif
 
+ifdef CONFIG_SMP
+prepare: task_cpu_prepare
+
+task_cpu_prepare: prepare0
+ $(eval KBUILD_CFLAGS += -D_TASK_CPU=$(shell awk '{if ($$2 == "TI_CPU") print $$3;}' include/generated/asm-offsets.h))
+endif
+
 # Check toolchain versions:
 # - gcc-4.6 is the minimum kernel-wide version so nothing required.
 checkbin:

arch/powerpc/include/asm/irq.h

@@ -51,9 +51,6 @@ struct pt_regs;
 extern struct thread_info *critirq_ctx[NR_CPUS];
 extern struct thread_info *dbgirq_ctx[NR_CPUS];
 extern struct thread_info *mcheckirq_ctx[NR_CPUS];
-extern void exc_lvl_ctx_init(void);
-#else
-#define exc_lvl_ctx_init()
 #endif
 
 /*
@@ -62,7 +59,6 @@ extern void exc_lvl_ctx_init(void);
 extern struct thread_info *hardirq_ctx[NR_CPUS];
 extern struct thread_info *softirq_ctx[NR_CPUS];
 
-extern void irq_ctx_init(void);
 void call_do_softirq(void *sp);
 void call_do_irq(struct pt_regs *regs, void *sp);
 extern void do_IRQ(struct pt_regs *regs);

arch/powerpc/include/asm/livepatch.h

@@ -21,6 +21,7 @@
 
 #include <linux/module.h>
 #include <linux/ftrace.h>
+#include <linux/sched/task_stack.h>
 
 #ifdef CONFIG_LIVEPATCH
 static inline int klp_check_compiler_support(void)
@@ -43,13 +44,13 @@ static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
  return ftrace_location_range(faddr, faddr + 16);
 }
 
-static inline void klp_init_thread_info(struct thread_info *ti)
+static inline void klp_init_thread_info(struct task_struct *p)
 {
  /* + 1 to account for STACK_END_MAGIC */
- ti->livepatch_sp = (unsigned long *)(ti + 1) + 1;
+ task_thread_info(p)->livepatch_sp = end_of_stack(p) + 1;
 }
 #else
-static void klp_init_thread_info(struct thread_info *ti) { }
+static inline void klp_init_thread_info(struct task_struct *p) { }
 #endif /* CONFIG_LIVEPATCH */
 
 #endif /* _ASM_POWERPC_LIVEPATCH_H */

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)

arch/powerpc/include/asm/thread_info.h

@@ -18,9 +18,9 @@
 #define THREAD_SIZE (1 << THREAD_SHIFT)
 
 #ifdef CONFIG_PPC64
-#define CURRENT_THREAD_INFO(dest, sp) stringify_in_c(clrrdi dest, sp, THREAD_SHIFT)
+#define CURRENT_THREAD_INFO(dest, sp) stringify_in_c(ld dest, PACACURRENT(r13))
 #else
-#define CURRENT_THREAD_INFO(dest, sp) stringify_in_c(rlwinm dest, sp, 0, 0, 31-THREAD_SHIFT)
+#define CURRENT_THREAD_INFO(dest, sp) stringify_in_c(mr dest, r2)
 #endif
 
 #ifndef __ASSEMBLY__
@@ -34,8 +34,6 @@
  * low level task data.
  */
 struct thread_info {
- struct task_struct *task; /* main task structure */
- int cpu; /* cpu we're on */
  int preempt_count; /* 0 => preemptable,
  <0 => BUG */
  unsigned long local_flags; /* private flags for thread */
@@ -58,24 +56,13 @@ struct thread_info {
  */
 #define INIT_THREAD_INFO(tsk) \
 { \
- .task = &tsk, \
- .cpu = 0, \
  .preempt_count = INIT_PREEMPT_COUNT, \
  .flags = 0, \
 }
 
 #define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT)
 
 /* how to get the thread information struct from C */
-static inline struct thread_info *current_thread_info(void)
-{
- unsigned long val;
-
- asm (CURRENT_THREAD_INFO(%0,1) : "=r" (val));
-
- return (struct thread_info *)val;
-}
-
 extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 
 #ifdef CONFIG_PPC_BOOK3S_64

arch/powerpc/kernel/asm-offsets.c

@@ -13,6 +13,8 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#define GENERATING_ASM_OFFSETS /* asm/smp.h */
+
 #include <linux/compat.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
@@ -97,6 +99,9 @@ int main(void)
 #endif
 #endif /* CONFIG_PPC64 */
  OFFSET(TASK_STACK, task_struct, stack);
+#ifdef CONFIG_SMP
+ OFFSET(TI_CPU, task_struct, cpu);
+#endif
 
 #ifdef CONFIG_LIVEPATCH
  OFFSET(TI_livepatch_sp, thread_info, livepatch_sp);
@@ -164,8 +169,6 @@ int main(void)
  OFFSET(TI_FLAGS, thread_info, flags);
  OFFSET(TI_LOCAL_FLAGS, thread_info, local_flags);
  OFFSET(TI_PREEMPT, thread_info, preempt_count);
- OFFSET(TI_TASK, thread_info, task);
- OFFSET(TI_CPU, thread_info, cpu);
 
 #ifdef CONFIG_PPC64
  OFFSET(DCACHEL1BLOCKSIZE, ppc64_caches, l1d.block_size);

arch/powerpc/kernel/entry_32.S

@@ -1165,10 +1165,6 @@ ret_from_debug_exc:
  mfspr r9,SPRN_SPRG_THREAD
  lwz r10,SAVED_KSP_LIMIT(r1)
  stw r10,KSP_LIMIT(r9)
- lwz r9,TASK_STACK-THREAD(r9)
- CURRENT_THREAD_INFO(r10, r1)
- lwz r10,TI_PREEMPT(r10)
- stw r10,TI_PREEMPT(r9)
  RESTORE_xSRR(SRR0,SRR1);
  RESTORE_xSRR(CSRR0,CSRR1);
  RESTORE_MMU_REGS;
@@ -1291,10 +1287,13 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_601)
  lwz r3,_TRAP(r1)
  andi. r0,r3,1
- beq 4f
+ beq 5f
  SAVE_NVGPRS(r1)
  rlwinm r3,r3,0,0,30
  stw r3,_TRAP(r1)
+5: mfspr r2,SPRN_SPRG_THREAD
+ addi r2,r2,-THREAD
+ tovirt(r2,r2) /* set back r2 to current */
 4: addi r3,r1,STACK_FRAME_OVERHEAD
  bl unrecoverable_exception
  /* shouldn't return */

arch/powerpc/kernel/exceptions-64e.S

@@ -77,17 +77,6 @@ special_reg_save:
  andi. r3,r3,MSR_PR
  bnelr
 
- /* Copy info into temporary exception thread info */
- ld r11,PACAKSAVE(r13)
- CURRENT_THREAD_INFO(r11, r11)
- CURRENT_THREAD_INFO(r12, r1)
- ld r10,TI_FLAGS(r11)
- std r10,TI_FLAGS(r12)
- ld r10,TI_PREEMPT(r11)
- std r10,TI_PREEMPT(r12)
- ld r10,TI_TASK(r11)
- std r10,TI_TASK(r12)
-
  /*
  * Advance to the next TLB exception frame for handler
  * types that don't do it automatically.

arch/powerpc/kernel/head_32.S

@@ -834,9 +834,9 @@ __secondary_start:
  /* get current's stack and current */
  lis r1,secondary_ti@ha
  tophys(r1,r1)
- lwz r1,secondary_ti@l(r1)
- tophys(r2,r1)
- lwz r2,TI_TASK(r2)
+ lwz r2,secondary_ti@l(r1)
+ tophys(r1,r2)
+ lwz r1,TASK_STACK(r1)
 
  /* stack */
  addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD

arch/powerpc/kernel/head_44x.S

@@ -1021,8 +1021,8 @@ _GLOBAL(start_secondary_47x)
 
  /* Get current's stack and current */
  lis r1,secondary_ti@ha
- lwz r1,secondary_ti@l(r1)
- lwz r2,TI_TASK(r1)
+ lwz r2,secondary_ti@l(r1)
+ lwz r1,TASK_STACK(r2)
 
  /* Current stack pointer */
  addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD

arch/powerpc/kernel/head_booke.h

@@ -155,13 +155,7 @@ END_BTB_FLUSH_SECTION
  stw r10,GPR11(r11); \
  b 2f; \
  /* COMING FROM PRIV MODE */ \
-1: lwz r9,TI_FLAGS-EXC_LVL_FRAME_OVERHEAD(r11); \
- lwz r10,TI_PREEMPT-EXC_LVL_FRAME_OVERHEAD(r11); \
- stw r9,TI_FLAGS-EXC_LVL_FRAME_OVERHEAD(r8); \
- stw r10,TI_PREEMPT-EXC_LVL_FRAME_OVERHEAD(r8); \
- lwz r9,TI_TASK-EXC_LVL_FRAME_OVERHEAD(r11); \
- stw r9,TI_TASK-EXC_LVL_FRAME_OVERHEAD(r8); \
- mr r11,r8; \
+1: mr r11, r8; \
 2: mfspr r8,SPRN_SPRG_RSCRATCH_##exc_level; \
  stw r12,GPR12(r11); /* save various registers */\
  mflr r10; \

arch/powerpc/kernel/head_fsl_booke.S

@@ -719,8 +719,7 @@ finish_tlb_load:
 
  /* Get the next_tlbcam_idx percpu var */
 #ifdef CONFIG_SMP
- lwz r12, TASK_STACK-THREAD(r12)
- lwz r15, TI_CPU(r12)
+ lwz r15, TI_CPU-THREAD(r12)
  lis r14, __per_cpu_offset@h
  ori r14, r14, __per_cpu_offset@l
  rlwinm r15, r15, 2, 0, 29
@@ -1093,8 +1092,8 @@ __secondary_start:
 
  /* get current's stack and current */
  lis r1,secondary_ti@ha
- lwz r1,secondary_ti@l(r1)
- lwz r2,TI_TASK(r1)
+ lwz r2,secondary_ti@l(r1)
+ lwz r1,TASK_STACK(r2)
 
  /* stack */
  addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD

arch/powerpc/kernel/irq.c

@@ -673,110 +673,33 @@ 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);
 }
 
 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)