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[MIPS] Fix aliasing bug in copy_to_user_page / copy_from_user_page

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The current implementation uses a sequence of a cacheflush and a copy.
This is racy in case of a multithreaded debuggee and renders GDB
virtually unusable.

Aside this fixes a performance hog rendering access to /proc/cmdline very
slow and resulting in a enough cache stalls for the 34K AP/SP programming
model to make the bare metal code on the non-Linux VPE miss RT deadlines.

The main part of this patch was originally written by Ralf Baechle;
Atushi Nemoto did the the debugging.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle
2006-10-21 23:17:35 +01:00
parent 224dc50ece
commit f8829caee3
5 changed files with 190 additions and 28 deletions
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167
arch/mips/mm/init.c
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@@ -30,11 +30,34 @@
#include <asm/cachectl.h>
#include <asm/cpu.h>
#include <asm/dma.h>
#include <asm/kmap_types.h>
#include <asm/mmu_context.h>
#include <asm/sections.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/fixmap.h>
/* Atomicity and interruptability */
#ifdef CONFIG_MIPS_MT_SMTC
#include <asm/mipsmtregs.h>
#define ENTER_CRITICAL(flags) \
{ \
unsigned int mvpflags; \
local_irq_save(flags);\
mvpflags = dvpe()
#define EXIT_CRITICAL(flags) \
evpe(mvpflags); \
local_irq_restore(flags); \
}
#else
#define ENTER_CRITICAL(flags) local_irq_save(flags)
#define EXIT_CRITICAL(flags) local_irq_restore(flags)
#endif /* CONFIG_MIPS_MT_SMTC */
DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
@@ -80,13 +103,142 @@ unsigned long setup_zero_pages(void)
return 1UL << order;
}
#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
pgprot_t kmap_prot;
/*
* These are almost like kmap_atomic / kunmap_atmic except they take an
* additional address argument as the hint.
*/
#define kmap_get_fixmap_pte(vaddr) \
pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))
#ifdef CONFIG_MIPS_MT_SMTC
static pte_t *kmap_coherent_pte;
static void __init kmap_coherent_init(void)
{
unsigned long vaddr;
/* cache the first coherent kmap pte */
vaddr = __fix_to_virt(FIX_CMAP_BEGIN);
kmap_coherent_pte = kmap_get_fixmap_pte(vaddr);
}
#else
static inline void kmap_coherent_init(void) {}
#endif
static inline void *kmap_coherent(struct page *page, unsigned long addr)
{
enum fixed_addresses idx;
unsigned long vaddr, flags, entrylo;
unsigned long old_ctx;
pte_t pte;
int tlbidx;
inc_preempt_count();
idx = (addr >> PAGE_SHIFT) & (FIX_N_COLOURS - 1);
#ifdef CONFIG_MIPS_MT_SMTC
idx += FIX_N_COLOURS * smp_processor_id();
#endif
vaddr = __fix_to_virt(FIX_CMAP_END - idx);
pte = mk_pte(page, PAGE_KERNEL);
#if defined(CONFIG_64BIT_PHYS_ADDR) && defined(CONFIG_CPU_MIPS32_R1)
entrylo = pte.pte_high;
#else
entrylo = pte_val(pte) >> 6;
#endif
ENTER_CRITICAL(flags);
old_ctx = read_c0_entryhi();
write_c0_entryhi(vaddr & (PAGE_MASK << 1));
write_c0_entrylo0(entrylo);
write_c0_entrylo1(entrylo);
#ifdef CONFIG_MIPS_MT_SMTC
set_pte(kmap_coherent_pte - (FIX_CMAP_END - idx), pte);
/* preload TLB instead of local_flush_tlb_one() */
mtc0_tlbw_hazard();
tlb_probe();
tlb_probe_hazard();
tlbidx = read_c0_index();
mtc0_tlbw_hazard();
if (tlbidx < 0)
tlb_write_random();
else
tlb_write_indexed();
#else
tlbidx = read_c0_wired();
write_c0_wired(tlbidx + 1);
write_c0_index(tlbidx);
mtc0_tlbw_hazard();
tlb_write_indexed();
#endif
tlbw_use_hazard();
write_c0_entryhi(old_ctx);
EXIT_CRITICAL(flags);
return (void*) vaddr;
}
#define UNIQUE_ENTRYHI(idx) (CKSEG0 + ((idx) << (PAGE_SHIFT + 1)))
static inline void kunmap_coherent(struct page *page)
{
#ifndef CONFIG_MIPS_MT_SMTC
unsigned int wired;
unsigned long flags, old_ctx;
ENTER_CRITICAL(flags);
old_ctx = read_c0_entryhi();
wired = read_c0_wired() - 1;
write_c0_wired(wired);
write_c0_index(wired);
write_c0_entryhi(UNIQUE_ENTRYHI(wired));
write_c0_entrylo0(0);
write_c0_entrylo1(0);
mtc0_tlbw_hazard();
tlb_write_indexed();
tlbw_use_hazard();
write_c0_entryhi(old_ctx);
EXIT_CRITICAL(flags);
#endif
dec_preempt_count();
preempt_check_resched();
}
void copy_to_user_page(struct vm_area_struct *vma,
struct page *page, unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
if (cpu_has_dc_aliases) {
void *vto = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(vto, src, len);
kunmap_coherent(page);
} else
memcpy(dst, src, len);
if ((vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc)
flush_cache_page(vma, vaddr, page_to_pfn(page));
}
EXPORT_SYMBOL(copy_to_user_page);
void copy_from_user_page(struct vm_area_struct *vma,
struct page *page, unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
if (cpu_has_dc_aliases) {
void *vfrom =
kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(dst, vfrom, len);
kunmap_coherent(page);
} else
memcpy(dst, src, len);
}
EXPORT_SYMBOL(copy_from_user_page);
#ifdef CONFIG_HIGHMEM
pte_t *kmap_pte;
pgprot_t kmap_prot;
static void __init kmap_init(void)
{
unsigned long kmap_vstart;
@@ -97,11 +249,12 @@ static void __init kmap_init(void)
kmap_prot = PAGE_KERNEL;
}
#endif /* CONFIG_HIGHMEM */
#ifdef CONFIG_32BIT
void __init fixrange_init(unsigned long start, unsigned long end,
pgd_t *pgd_base)
{
#if defined(CONFIG_HIGHMEM) || defined(CONFIG_MIPS_MT_SMTC)
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
@@ -122,7 +275,7 @@ void __init fixrange_init(unsigned long start, unsigned long end,
for (; (k < PTRS_PER_PMD) && (vaddr != end); pmd++, k++) {
if (pmd_none(*pmd)) {
pte = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
set_pmd(pmd, __pmd(pte));
set_pmd(pmd, __pmd((unsigned long)pte));
if (pte != pte_offset_kernel(pmd, 0))
BUG();
}
@@ -132,9 +285,8 @@ void __init fixrange_init(unsigned long start, unsigned long end,
}
j = 0;
}
#endif
}
#endif /* CONFIG_32BIT */
#endif /* CONFIG_HIGHMEM */
#ifndef CONFIG_NEED_MULTIPLE_NODES
extern void pagetable_init(void);
@@ -175,6 +327,7 @@ void __init paging_init(void)
#ifdef CONFIG_HIGHMEM
kmap_init();
#endif
kmap_coherent_init();
max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
low = max_low_pfn;