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>
This commit is contained in:
Christophe Leroy 2019-01-31 10:08:58 +00:00 committed by Michael Ellerman
parent 7aef376679
commit ed1cd6deb0
21 changed files with 56 additions and 194 deletions

View File

@ -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.

View File

@ -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:

View File

@ -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);

View File

@ -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 */

View File

@ -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)

View File

@ -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 */
@ -58,8 +56,6 @@ struct thread_info {
*/
#define INIT_THREAD_INFO(tsk) \
{ \
.task = &tsk, \
.cpu = 0, \
.preempt_count = INIT_PREEMPT_COUNT, \
.flags = 0, \
}
@ -67,15 +63,6 @@ struct thread_info {
#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

View File

@ -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);

View File

@ -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 */

View File

@ -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.

View File

@ -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

View File

@ -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

View File

@ -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; \

View File

@ -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

View File

@ -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)

View File

@ -151,41 +151,13 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
return 1;
}
static DEFINE_PER_CPU(struct thread_info, kgdb_thread_info);
static int kgdb_singlestep(struct pt_regs *regs)
{
struct thread_info *thread_info, *exception_thread_info;
struct thread_info *backup_current_thread_info =
this_cpu_ptr(&kgdb_thread_info);
if (user_mode(regs))
return 0;
/*
* On Book E and perhaps other processors, singlestep is handled on
* the critical exception stack. This causes current_thread_info()
* to fail, since it it locates the thread_info by masking off
* the low bits of the current stack pointer. We work around
* this issue by copying the thread_info from the kernel stack
* before calling kgdb_handle_exception, and copying it back
* afterwards. On most processors the copy is avoided since
* exception_thread_info == thread_info.
*/
thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
exception_thread_info = current_thread_info();
if (thread_info != exception_thread_info) {
/* Save the original current_thread_info. */
memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
memcpy(exception_thread_info, thread_info, sizeof *thread_info);
}
kgdb_handle_exception(0, SIGTRAP, 0, regs);
if (thread_info != exception_thread_info)
/* Restore current_thread_info lastly. */
memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
return 1;
}

View File

@ -317,10 +317,8 @@ void default_machine_kexec(struct kimage *image)
* We setup preempt_count to avoid using VMX in memcpy.
* XXX: the task struct will likely be invalid once we do the copy!
*/
kexec_stack.thread_info.task = current_thread_info()->task;
kexec_stack.thread_info.flags = 0;
kexec_stack.thread_info.preempt_count = HARDIRQ_OFFSET;
kexec_stack.thread_info.cpu = current_thread_info()->cpu;
current_thread_info()->flags = 0;
current_thread_info()->preempt_count = HARDIRQ_OFFSET;
/* We need a static PACA, too; copy this CPU's PACA over and switch to
* it. Also poison per_cpu_offset and NULL lppaca to catch anyone using

View File

@ -1634,7 +1634,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
struct thread_info *ti = task_thread_info(p);
klp_init_thread_info(ti);
klp_init_thread_info(p);
/* Copy registers */
sp -= sizeof(struct pt_regs);

View File

@ -937,7 +937,7 @@ void __init setup_arch(char **cmdline_p)
/* Reserve large chunks of memory for use by CMA for KVM. */
kvm_cma_reserve();
klp_init_thread_info(&init_thread_info);
klp_init_thread_info(&init_task);
init_mm.start_code = (unsigned long)_stext;
init_mm.end_code = (unsigned long) _etext;

View File

@ -689,24 +689,6 @@ void __init exc_lvl_early_init(void)
}
#endif
/*
* Emergency stacks are used for a range of things, from asynchronous
* NMIs (system reset, machine check) to synchronous, process context.
* We set preempt_count to zero, even though that isn't necessarily correct. To
* get the right value we'd need to copy it from the previous thread_info, but
* doing that might fault causing more problems.
* TODO: what to do with accounting?
*/
static void emerg_stack_init_thread_info(struct thread_info *ti, int cpu)
{
ti->task = NULL;
ti->cpu = cpu;
ti->preempt_count = 0;
ti->local_flags = 0;
ti->flags = 0;
klp_init_thread_info(ti);
}
/*
* Stack space used when we detect a bad kernel stack pointer, and
* early in SMP boots before relocation is enabled. Exclusive emergency
@ -737,18 +719,15 @@ void __init emergency_stack_init(void)
struct thread_info *ti;
ti = alloc_stack(limit, i);
emerg_stack_init_thread_info(ti, i);
paca_ptrs[i]->emergency_sp = (void *)ti + THREAD_SIZE;
#ifdef CONFIG_PPC_BOOK3S_64
/* emergency stack for NMI exception handling. */
ti = alloc_stack(limit, i);
emerg_stack_init_thread_info(ti, i);
paca_ptrs[i]->nmi_emergency_sp = (void *)ti + THREAD_SIZE;
/* emergency stack for machine check exception handling. */
ti = alloc_stack(limit, i);
emerg_stack_init_thread_info(ti, i);
paca_ptrs[i]->mc_emergency_sp = (void *)ti + THREAD_SIZE;
#endif
}

View File

@ -988,7 +988,7 @@ static void cpu_idle_thread_init(unsigned int cpu, struct task_struct *idle)
paca_ptrs[cpu]->kstack = (unsigned long)task_stack_page(idle) +
THREAD_SIZE - STACK_FRAME_OVERHEAD;
#endif
ti->cpu = cpu;
idle->cpu = cpu;
secondary_ti = current_set[cpu] = ti;
}

View File

@ -106,9 +106,8 @@ DECLARE_LOAD_FUNC(sk_load_byte_msh);
} while (0)
#else
#define PPC_BPF_LOAD_CPU(r) \
do { BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info, cpu) != 4); \
PPC_LHZ_OFFS(r, (1 & ~(THREAD_SIZE - 1)), \
offsetof(struct thread_info, cpu)); \
do { BUILD_BUG_ON(FIELD_SIZEOF(struct task_struct, cpu) != 4); \
PPC_LHZ_OFFS(r, 2, offsetof(struct task_struct, cpu)); \
} while(0)
#endif
#else