UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity
OpenCloudOS-Kernel/arch/powerpc/mm/slb.c

829 lines
22 KiB
C
Raw Blame History

/*
* PowerPC64 SLB support.
*
* Copyright (C) 2004 David Gibson <dwg@au.ibm.com>, IBM
* Based on earlier code written by:
* Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
* Copyright (c) 2001 Dave Engebretsen
* Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <asm/asm-prototypes.h>
#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/paca.h>
#include <asm/cputable.h>
#include <asm/cacheflush.h>
#include <asm/smp.h>
#include <linux/compiler.h>
#include <linux/context_tracking.h>
#include <linux/mm_types.h>
#include <asm/udbg.h>
#include <asm/code-patching.h>
enum slb_index {
LINEAR_INDEX = 0, /* Kernel linear map (0xc000000000000000) */
KSTACK_INDEX = 1, /* Kernel stack map */
};
static long slb_allocate_user(struct mm_struct *mm, unsigned long ea);
#define slb_esid_mask(ssize) \
(((ssize) == MMU_SEGSIZE_256M)? ESID_MASK: ESID_MASK_1T)
static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
enum slb_index index)
{
return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | index;
}
static inline unsigned long __mk_vsid_data(unsigned long vsid, int ssize,
unsigned long flags)
{
return (vsid << slb_vsid_shift(ssize)) | flags |
((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
}
static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
unsigned long flags)
{
return __mk_vsid_data(get_kernel_vsid(ea, ssize), ssize, flags);
}
static void assert_slb_exists(unsigned long ea)
{
#ifdef CONFIG_DEBUG_VM
unsigned long tmp;
WARN_ON_ONCE(mfmsr() & MSR_EE);
asm volatile("slbfee. %0, %1" : "=r"(tmp) : "r"(ea) : "cr0");
WARN_ON(tmp == 0);
#endif
}
static void assert_slb_notexists(unsigned long ea)
{
#ifdef CONFIG_DEBUG_VM
unsigned long tmp;
WARN_ON_ONCE(mfmsr() & MSR_EE);
asm volatile("slbfee. %0, %1" : "=r"(tmp) : "r"(ea) : "cr0");
WARN_ON(tmp != 0);
#endif
}
static inline void slb_shadow_update(unsigned long ea, int ssize,
unsigned long flags,
enum slb_index index)
{
struct slb_shadow *p = get_slb_shadow();
/*
* Clear the ESID first so the entry is not valid while we are
* updating it. No write barriers are needed here, provided
* we only update the current CPU's SLB shadow buffer.
*/
WRITE_ONCE(p->save_area[index].esid, 0);
WRITE_ONCE(p->save_area[index].vsid, cpu_to_be64(mk_vsid_data(ea, ssize, flags)));
WRITE_ONCE(p->save_area[index].esid, cpu_to_be64(mk_esid_data(ea, ssize, index)));
}
static inline void slb_shadow_clear(enum slb_index index)
{
WRITE_ONCE(get_slb_shadow()->save_area[index].esid, cpu_to_be64(index));
}
static inline void create_shadowed_slbe(unsigned long ea, int ssize,
unsigned long flags,
enum slb_index index)
{
/*
* Updating the shadow buffer before writing the SLB ensures
* we don't get a stale entry here if we get preempted by PHYP
* between these two statements.
*/
slb_shadow_update(ea, ssize, flags, index);
assert_slb_notexists(ea);
asm volatile("slbmte %0,%1" :
: "r" (mk_vsid_data(ea, ssize, flags)),
"r" (mk_esid_data(ea, ssize, index))
: "memory" );
}
/*
* Insert bolted entries into SLB (which may not be empty, so don't clear
* slb_cache_ptr).
*/
void __slb_restore_bolted_realmode(void)
{
struct slb_shadow *p = get_slb_shadow();
enum slb_index index;
/* No isync needed because realmode. */
for (index = 0; index < SLB_NUM_BOLTED; index++) {
asm volatile("slbmte %0,%1" :
: "r" (be64_to_cpu(p->save_area[index].vsid)),
"r" (be64_to_cpu(p->save_area[index].esid)));
}
assert_slb_exists(local_paca->kstack);
}
/*
* Insert the bolted entries into an empty SLB.
*/
void slb_restore_bolted_realmode(void)
{
__slb_restore_bolted_realmode();
get_paca()->slb_cache_ptr = 0;
get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
}
/*
* This flushes all SLB entries including 0, so it must be realmode.
*/
void slb_flush_all_realmode(void)
{
asm volatile("slbmte %0,%0; slbia" : : "r" (0));
}
/*
* This flushes non-bolted entries, it can be run in virtual mode. Must
* be called with interrupts disabled.
*/
void slb_flush_and_restore_bolted(void)
{
struct slb_shadow *p = get_slb_shadow();
BUILD_BUG_ON(SLB_NUM_BOLTED != 2);
WARN_ON(!irqs_disabled());
/*
* We can't take a PMU exception in the following code, so hard
* disable interrupts.
*/
hard_irq_disable();
asm volatile("isync\n"
"slbia\n"
"slbmte %0, %1\n"
"isync\n"
:: "r" (be64_to_cpu(p->save_area[KSTACK_INDEX].vsid)),
"r" (be64_to_cpu(p->save_area[KSTACK_INDEX].esid))
: "memory");
assert_slb_exists(get_paca()->kstack);
get_paca()->slb_cache_ptr = 0;
get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
}
void slb_save_contents(struct slb_entry *slb_ptr)
{
int i;
unsigned long e, v;
/* Save slb_cache_ptr value. */
get_paca()->slb_save_cache_ptr = get_paca()->slb_cache_ptr;
if (!slb_ptr)
return;
for (i = 0; i < mmu_slb_size; i++) {
asm volatile("slbmfee %0,%1" : "=r" (e) : "r" (i));
asm volatile("slbmfev %0,%1" : "=r" (v) : "r" (i));
slb_ptr->esid = e;
slb_ptr->vsid = v;
slb_ptr++;
}
}
void slb_dump_contents(struct slb_entry *slb_ptr)
{
int i, n;
unsigned long e, v;
unsigned long llp;
if (!slb_ptr)
return;
pr_err("SLB contents of cpu 0x%x\n", smp_processor_id());
pr_err("Last SLB entry inserted at slot %d\n", get_paca()->stab_rr);
for (i = 0; i < mmu_slb_size; i++) {
e = slb_ptr->esid;
v = slb_ptr->vsid;
slb_ptr++;
if (!e && !v)
continue;
pr_err("%02d %016lx %016lx\n", i, e, v);
if (!(e & SLB_ESID_V)) {
pr_err("\n");
continue;
}
llp = v & SLB_VSID_LLP;
if (v & SLB_VSID_B_1T) {
pr_err(" 1T ESID=%9lx VSID=%13lx LLP:%3lx\n",
GET_ESID_1T(e),
(v & ~SLB_VSID_B) >> SLB_VSID_SHIFT_1T, llp);
} else {
pr_err(" 256M ESID=%9lx VSID=%13lx LLP:%3lx\n",
GET_ESID(e),
(v & ~SLB_VSID_B) >> SLB_VSID_SHIFT, llp);
}
}
pr_err("----------------------------------\n");
/* Dump slb cache entires as well. */
pr_err("SLB cache ptr value = %d\n", get_paca()->slb_save_cache_ptr);
pr_err("Valid SLB cache entries:\n");
n = min_t(int, get_paca()->slb_save_cache_ptr, SLB_CACHE_ENTRIES);
for (i = 0; i < n; i++)
pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
pr_err("Rest of SLB cache entries:\n");
for (i = n; i < SLB_CACHE_ENTRIES; i++)
pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
}
void slb_vmalloc_update(void)
{
/*
* vmalloc is not bolted, so just have to flush non-bolted.
*/
slb_flush_and_restore_bolted();
}
static bool preload_hit(struct thread_info *ti, unsigned long esid)
{
unsigned char i;
for (i = 0; i < ti->slb_preload_nr; i++) {
unsigned char idx;
idx = (ti->slb_preload_tail + i) % SLB_PRELOAD_NR;
if (esid == ti->slb_preload_esid[idx])
return true;
}
return false;
}
static bool preload_add(struct thread_info *ti, unsigned long ea)
{
unsigned char idx;
unsigned long esid;
if (mmu_has_feature(MMU_FTR_1T_SEGMENT)) {
/* EAs are stored >> 28 so 256MB segments don't need clearing */
if (ea & ESID_MASK_1T)
ea &= ESID_MASK_1T;
}
esid = ea >> SID_SHIFT;
if (preload_hit(ti, esid))
return false;
idx = (ti->slb_preload_tail + ti->slb_preload_nr) % SLB_PRELOAD_NR;
ti->slb_preload_esid[idx] = esid;
if (ti->slb_preload_nr == SLB_PRELOAD_NR)
ti->slb_preload_tail = (ti->slb_preload_tail + 1) % SLB_PRELOAD_NR;
else
ti->slb_preload_nr++;
return true;
}
static void preload_age(struct thread_info *ti)
{
if (!ti->slb_preload_nr)
return;
ti->slb_preload_nr--;
ti->slb_preload_tail = (ti->slb_preload_tail + 1) % SLB_PRELOAD_NR;
}
void slb_setup_new_exec(void)
{
struct thread_info *ti = current_thread_info();
struct mm_struct *mm = current->mm;
unsigned long exec = 0x10000000;
WARN_ON(irqs_disabled());
/*
* preload cache can only be used to determine whether a SLB
* entry exists if it does not start to overflow.
*/
if (ti->slb_preload_nr + 2 > SLB_PRELOAD_NR)
return;
hard_irq_disable();
/*
* We have no good place to clear the slb preload cache on exec,
* flush_thread is about the earliest arch hook but that happens
* after we switch to the mm and have aleady preloaded the SLBEs.
*
* For the most part that's probably okay to use entries from the
* previous exec, they will age out if unused. It may turn out to
* be an advantage to clear the cache before switching to it,
* however.
*/
/*
* preload some userspace segments into the SLB.
* Almost all 32 and 64bit PowerPC executables are linked at
* 0x10000000 so it makes sense to preload this segment.
*/
if (!is_kernel_addr(exec)) {
if (preload_add(ti, exec))
slb_allocate_user(mm, exec);
}
/* Libraries and mmaps. */
if (!is_kernel_addr(mm->mmap_base)) {
if (preload_add(ti, mm->mmap_base))
slb_allocate_user(mm, mm->mmap_base);
}
/* see switch_slb */
asm volatile("isync" : : : "memory");
local_irq_enable();
}
void preload_new_slb_context(unsigned long start, unsigned long sp)
{
struct thread_info *ti = current_thread_info();
struct mm_struct *mm = current->mm;
unsigned long heap = mm->start_brk;
WARN_ON(irqs_disabled());
/* see above */
if (ti->slb_preload_nr + 3 > SLB_PRELOAD_NR)
return;
hard_irq_disable();
/* Userspace entry address. */
if (!is_kernel_addr(start)) {
if (preload_add(ti, start))
slb_allocate_user(mm, start);
}
/* Top of stack, grows down. */
if (!is_kernel_addr(sp)) {
if (preload_add(ti, sp))
slb_allocate_user(mm, sp);
}
/* Bottom of heap, grows up. */
if (heap && !is_kernel_addr(heap)) {
if (preload_add(ti, heap))
slb_allocate_user(mm, heap);
}
/* see switch_slb */
asm volatile("isync" : : : "memory");
local_irq_enable();
}
/* Flush all user entries from the segment table of the current processor. */
void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
{
struct thread_info *ti = task_thread_info(tsk);
unsigned char i;
/*
* We need interrupts hard-disabled here, not just soft-disabled,
* so that a PMU interrupt can't occur, which might try to access
* user memory (to get a stack trace) and possible cause an SLB miss
* which would update the slb_cache/slb_cache_ptr fields in the PACA.
*/
hard_irq_disable();
asm volatile("isync" : : : "memory");
if (cpu_has_feature(CPU_FTR_ARCH_300)) {
/*
* SLBIA IH=3 invalidates all Class=1 SLBEs and their
* associated lookaside structures, which matches what
* switch_slb wants. So ARCH_300 does not use the slb
* cache.
*/
asm volatile(PPC_SLBIA(3));
} else {
unsigned long offset = get_paca()->slb_cache_ptr;
if (!mmu_has_feature(MMU_FTR_NO_SLBIE_B) &&
offset <= SLB_CACHE_ENTRIES) {
unsigned long slbie_data = 0;
for (i = 0; i < offset; i++) {
unsigned long ea;
ea = (unsigned long)
get_paca()->slb_cache[i] << SID_SHIFT;
/*
* Could assert_slb_exists here, but hypervisor
* or machine check could have come in and
* removed the entry at this point.
*/
slbie_data = ea;
slbie_data |= user_segment_size(slbie_data)
<< SLBIE_SSIZE_SHIFT;
slbie_data |= SLBIE_C; /* user slbs have C=1 */
asm volatile("slbie %0" : : "r" (slbie_data));
}
/* Workaround POWER5 < DD2.1 issue */
if (!cpu_has_feature(CPU_FTR_ARCH_207S) && offset == 1)
asm volatile("slbie %0" : : "r" (slbie_data));
} else {
struct slb_shadow *p = get_slb_shadow();
unsigned long ksp_esid_data =
be64_to_cpu(p->save_area[KSTACK_INDEX].esid);
unsigned long ksp_vsid_data =
be64_to_cpu(p->save_area[KSTACK_INDEX].vsid);
asm volatile(PPC_SLBIA(1) "\n"
"slbmte %0,%1\n"
"isync"
:: "r"(ksp_vsid_data),
"r"(ksp_esid_data));
get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
}
get_paca()->slb_cache_ptr = 0;
}
get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
copy_mm_to_paca(mm);
/*
* We gradually age out SLBs after a number of context switches to
* reduce reload overhead of unused entries (like we do with FP/VEC
* reload). Each time we wrap 256 switches, take an entry out of the
* SLB preload cache.
*/
tsk->thread.load_slb++;
if (!tsk->thread.load_slb) {
unsigned long pc = KSTK_EIP(tsk);
preload_age(ti);
preload_add(ti, pc);
}
for (i = 0; i < ti->slb_preload_nr; i++) {
unsigned char idx;
unsigned long ea;
idx = (ti->slb_preload_tail + i) % SLB_PRELOAD_NR;
ea = (unsigned long)ti->slb_preload_esid[idx] << SID_SHIFT;
slb_allocate_user(mm, ea);
}
/*
* Synchronize slbmte preloads with possible subsequent user memory
* address accesses by the kernel (user mode won't happen until
* rfid, which is safe).
*/
asm volatile("isync" : : : "memory");
}
void slb_set_size(u16 size)
{
mmu_slb_size = size;
}
void slb_initialize(void)
{
unsigned long linear_llp, vmalloc_llp, io_llp;
unsigned long lflags;
static int slb_encoding_inited;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
unsigned long vmemmap_llp;
#endif
/* Prepare our SLB miss handler based on our page size */
linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
io_llp = mmu_psize_defs[mmu_io_psize].sllp;
vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
get_paca()->vmalloc_sllp = SLB_VSID_KERNEL | vmalloc_llp;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
vmemmap_llp = mmu_psize_defs[mmu_vmemmap_psize].sllp;
#endif
if (!slb_encoding_inited) {
slb_encoding_inited = 1;
pr_devel("SLB: linear LLP = %04lx\n", linear_llp);
pr_devel("SLB: io LLP = %04lx\n", io_llp);
#ifdef CONFIG_SPARSEMEM_VMEMMAP
pr_devel("SLB: vmemmap LLP = %04lx\n", vmemmap_llp);
#endif
}
get_paca()->stab_rr = SLB_NUM_BOLTED - 1;
get_paca()->slb_kern_bitmap = (1U << SLB_NUM_BOLTED) - 1;
get_paca()->slb_used_bitmap = get_paca()->slb_kern_bitmap;
lflags = SLB_VSID_KERNEL | linear_llp;
/* Invalidate the entire SLB (even entry 0) & all the ERATS */
asm volatile("isync":::"memory");
asm volatile("slbmte %0,%0"::"r" (0) : "memory");
asm volatile("isync; slbia; isync":::"memory");
create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, LINEAR_INDEX);
/* For the boot cpu, we're running on the stack in init_thread_union,
* which is in the first segment of the linear mapping, and also
* get_paca()->kstack hasn't been initialized yet.
* For secondary cpus, we need to bolt the kernel stack entry now.
*/
slb_shadow_clear(KSTACK_INDEX);
if (raw_smp_processor_id() != boot_cpuid &&
(get_paca()->kstack & slb_esid_mask(mmu_kernel_ssize)) > PAGE_OFFSET)
create_shadowed_slbe(get_paca()->kstack,
mmu_kernel_ssize, lflags, KSTACK_INDEX);
asm volatile("isync":::"memory");
}
static void slb_cache_update(unsigned long esid_data)
{
int slb_cache_index;
if (cpu_has_feature(CPU_FTR_ARCH_300))
return; /* ISAv3.0B and later does not use slb_cache */
/*
* Now update slb cache entries
*/
slb_cache_index = local_paca->slb_cache_ptr;
if (slb_cache_index < SLB_CACHE_ENTRIES) {
/*
* We have space in slb cache for optimized switch_slb().
* Top 36 bits from esid_data as per ISA
*/
local_paca->slb_cache[slb_cache_index++] = esid_data >> 28;
local_paca->slb_cache_ptr++;
} else {
/*
* Our cache is full and the current cache content strictly
* doesn't indicate the active SLB conents. Bump the ptr
* so that switch_slb() will ignore the cache.
*/
local_paca->slb_cache_ptr = SLB_CACHE_ENTRIES + 1;
}
}
static enum slb_index alloc_slb_index(bool kernel)
{
enum slb_index index;
/*
* The allocation bitmaps can become out of synch with the SLB
* when the _switch code does slbie when bolting a new stack
* segment and it must not be anywhere else in the SLB. This leaves
* a kernel allocated entry that is unused in the SLB. With very
* large systems or small segment sizes, the bitmaps could slowly
* fill with these entries. They will eventually be cleared out
* by the round robin allocator in that case, so it's probably not
* worth accounting for.
*/
/*
* SLBs beyond 32 entries are allocated with stab_rr only
* POWER7/8/9 have 32 SLB entries, this could be expanded if a
* future CPU has more.
*/
if (local_paca->slb_used_bitmap != U32_MAX) {
index = ffz(local_paca->slb_used_bitmap);
local_paca->slb_used_bitmap |= 1U << index;
if (kernel)
local_paca->slb_kern_bitmap |= 1U << index;
} else {
/* round-robin replacement of slb starting at SLB_NUM_BOLTED. */
index = local_paca->stab_rr;
if (index < (mmu_slb_size - 1))
index++;
else
index = SLB_NUM_BOLTED;
local_paca->stab_rr = index;
if (index < 32) {
if (kernel)
local_paca->slb_kern_bitmap |= 1U << index;
else
local_paca->slb_kern_bitmap &= ~(1U << index);
}
}
BUG_ON(index < SLB_NUM_BOLTED);
return index;
}
static long slb_insert_entry(unsigned long ea, unsigned long context,
unsigned long flags, int ssize, bool kernel)
{
unsigned long vsid;
unsigned long vsid_data, esid_data;
enum slb_index index;
vsid = get_vsid(context, ea, ssize);
if (!vsid)
return -EFAULT;
/*
* There must not be a kernel SLB fault in alloc_slb_index or before
* slbmte here or the allocation bitmaps could get out of whack with
* the SLB.
*
* User SLB faults or preloads take this path which might get inlined
* into the caller, so add compiler barriers here to ensure unsafe
* memory accesses do not come between.
*/
barrier();
index = alloc_slb_index(kernel);
vsid_data = __mk_vsid_data(vsid, ssize, flags);
esid_data = mk_esid_data(ea, ssize, index);
/*
* No need for an isync before or after this slbmte. The exception
* we enter with and the rfid we exit with are context synchronizing.
* User preloads should add isync afterwards in case the kernel
* accesses user memory before it returns to userspace with rfid.
*/
assert_slb_notexists(ea);
asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data));
barrier();
if (!kernel)
slb_cache_update(esid_data);
return 0;
}
static long slb_allocate_kernel(unsigned long ea, unsigned long id)
{
unsigned long context;
unsigned long flags;
int ssize;
if (id == KERNEL_REGION_ID) {
/* We only support upto MAX_PHYSMEM_BITS */
if ((ea & ~REGION_MASK) > (1UL << MAX_PHYSMEM_BITS))
return -EFAULT;
flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_linear_psize].sllp;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
} else if (id == VMEMMAP_REGION_ID) {
if ((ea & ~REGION_MASK) >= (1ULL << MAX_EA_BITS_PER_CONTEXT))
return -EFAULT;
flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_vmemmap_psize].sllp;
#endif
} else if (id == VMALLOC_REGION_ID) {
if ((ea & ~REGION_MASK) >= (1ULL << MAX_EA_BITS_PER_CONTEXT))
return -EFAULT;
if (ea < H_VMALLOC_END)
flags = get_paca()->vmalloc_sllp;
else
flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_io_psize].sllp;
} else {
return -EFAULT;
}
ssize = MMU_SEGSIZE_1T;
if (!mmu_has_feature(MMU_FTR_1T_SEGMENT))
ssize = MMU_SEGSIZE_256M;
context = get_kernel_context(ea);
return slb_insert_entry(ea, context, flags, ssize, true);
}
static long slb_allocate_user(struct mm_struct *mm, unsigned long ea)
{
unsigned long context;
unsigned long flags;
int bpsize;
int ssize;
/*
* consider this as bad access if we take a SLB miss
* on an address above addr limit.
*/
if (ea >= mm->context.slb_addr_limit)
return -EFAULT;
context = get_user_context(&mm->context, ea);
if (!context)
return -EFAULT;
if (unlikely(ea >= H_PGTABLE_RANGE)) {
WARN_ON(1);
return -EFAULT;
}
ssize = user_segment_size(ea);
bpsize = get_slice_psize(mm, ea);
flags = SLB_VSID_USER | mmu_psize_defs[bpsize].sllp;
return slb_insert_entry(ea, context, flags, ssize, false);
}
long do_slb_fault(struct pt_regs *regs, unsigned long ea)
{
unsigned long id = REGION_ID(ea);
/* IRQs are not reconciled here, so can't check irqs_disabled */
VM_WARN_ON(mfmsr() & MSR_EE);
if (unlikely(!(regs->msr & MSR_RI)))
return -EINVAL;
/*
* SLB kernel faults must be very careful not to touch anything
* that is not bolted. E.g., PACA and global variables are okay,
* mm->context stuff is not.
*
* SLB user faults can access all of kernel memory, but must be
* careful not to touch things like IRQ state because it is not
* "reconciled" here. The difficulty is that we must use
* fast_exception_return to return from kernel SLB faults without
* looking at possible non-bolted memory. We could test user vs
* kernel faults in the interrupt handler asm and do a full fault,
* reconcile, ret_from_except for user faults which would make them
* first class kernel code. But for performance it's probably nicer
* if they go via fast_exception_return too.
*/
if (id >= KERNEL_REGION_ID) {
long err;
#ifdef CONFIG_DEBUG_VM
/* Catch recursive kernel SLB faults. */
BUG_ON(local_paca->in_kernel_slb_handler);
local_paca->in_kernel_slb_handler = 1;
#endif
err = slb_allocate_kernel(ea, id);
#ifdef CONFIG_DEBUG_VM
local_paca->in_kernel_slb_handler = 0;
#endif
return err;
} else {
struct mm_struct *mm = current->mm;
long err;
if (unlikely(!mm))
return -EFAULT;
err = slb_allocate_user(mm, ea);
if (!err)
preload_add(current_thread_info(), ea);
return err;
}
}
void do_bad_slb_fault(struct pt_regs *regs, unsigned long ea, long err)
{
if (err == -EFAULT) {
if (user_mode(regs))
_exception(SIGSEGV, regs, SEGV_BNDERR, ea);
else
bad_page_fault(regs, ea, SIGSEGV);
} else if (err == -EINVAL) {
unrecoverable_exception(regs);
} else {
BUG();
}
}
Reference in New Issue View Git Blame Copy Permalink