access_process_vm device memory infrastructure
In order to be able to debug things like the X server and programs using
the PPC Cell SPUs, the debugger needs to be able to access device memory
through ptrace and /proc/pid/mem.
This patch:
Add the generic_access_phys access function and put the hooks in place
to allow access_process_vm to access device or PPC Cell SPU memory.
[riel@redhat.com: Add documentation for the vm_ops->access function]
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Benjamin Herrensmidt <benh@kernel.crashing.org>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 8b22d7d8..680fb56 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -510,6 +510,7 @@
void (*close)(struct vm_area_struct*);
int (*fault)(struct vm_area_struct*, struct vm_fault *);
int (*page_mkwrite)(struct vm_area_struct *, struct page *);
+ int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
locking rules:
BKL mmap_sem PageLocked(page)
@@ -517,6 +518,7 @@
close: no yes
fault: no yes
page_mkwrite: no yes no
+access: no yes
->page_mkwrite() is called when a previously read-only page is
about to become writeable. The file system is responsible for
@@ -525,6 +527,11 @@
within i_size. The page mapping should also be checked that it is not
NULL.
+ ->access() is called when get_user_pages() fails in
+acces_process_vm(), typically used to debug a process through
+/proc/pid/mem or ptrace. This function is needed only for
+VM_IO | VM_PFNMAP VMAs.
+
================================================================================
Dubious stuff
diff --git a/arch/Kconfig b/arch/Kconfig
index 4d5ebbc..6093c0b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -31,6 +31,9 @@
def_bool y
depends on KPROBES && HAVE_KRETPROBES
+config HAVE_IOREMAP_PROT
+ def_bool n
+
config HAVE_KPROBES
def_bool n
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 03980cb..b2ddfcf 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -21,6 +21,7 @@
select HAVE_UNSTABLE_SCHED_CLOCK
select HAVE_IDE
select HAVE_OPROFILE
+ select HAVE_IOREMAP_PROT
select HAVE_KPROBES
select HAVE_KRETPROBES
select HAVE_DYNAMIC_FTRACE
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 24c1d3c..016f335 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -330,6 +330,14 @@
return (void __iomem *)ret;
}
+void __iomem *ioremap_prot(resource_size_t phys_addr, unsigned long size,
+ unsigned long prot_val)
+{
+ return __ioremap_caller(phys_addr, size, (prot_val & _PAGE_CACHE_MASK),
+ __builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_prot);
+
/**
* iounmap - Free a IO remapping
* @addr: virtual address from ioremap_*
diff --git a/include/asm-x86/io_32.h b/include/asm-x86/io_32.h
index 4df44ed..e876d89 100644
--- a/include/asm-x86/io_32.h
+++ b/include/asm-x86/io_32.h
@@ -110,6 +110,8 @@
*/
extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size);
extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size,
+ unsigned long prot_val);
/*
* The default ioremap() behavior is non-cached:
diff --git a/include/asm-x86/io_64.h b/include/asm-x86/io_64.h
index ddd8058..22995c5 100644
--- a/include/asm-x86/io_64.h
+++ b/include/asm-x86/io_64.h
@@ -175,6 +175,8 @@
*/
extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size);
extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size,
+ unsigned long prot_val);
/*
* The default ioremap() behavior is non-cached:
diff --git a/include/linux/mm.h b/include/linux/mm.h
index eb815cf..5c7f8f6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -170,6 +170,12 @@
/* notification that a previously read-only page is about to become
* writable, if an error is returned it will cause a SIGBUS */
int (*page_mkwrite)(struct vm_area_struct *vma, struct page *page);
+
+ /* called by access_process_vm when get_user_pages() fails, typically
+ * for use by special VMAs that can switch between memory and hardware
+ */
+ int (*access)(struct vm_area_struct *vma, unsigned long addr,
+ void *buf, int len, int write);
#ifdef CONFIG_NUMA
/*
* set_policy() op must add a reference to any non-NULL @new mempolicy
@@ -771,6 +777,8 @@
struct vm_area_struct *vma);
void unmap_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen, int even_cows);
+int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+ void *buf, int len, int write);
static inline void unmap_shared_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen)
diff --git a/mm/memory.c b/mm/memory.c
index 46dbed4..8735032 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2751,6 +2751,86 @@
#endif /* __HAVE_ARCH_GATE_AREA */
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+static resource_size_t follow_phys(struct vm_area_struct *vma,
+ unsigned long address, unsigned int flags,
+ unsigned long *prot)
+{
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *ptep, pte;
+ spinlock_t *ptl;
+ resource_size_t phys_addr = 0;
+ struct mm_struct *mm = vma->vm_mm;
+
+ VM_BUG_ON(!(vma->vm_flags & (VM_IO | VM_PFNMAP)));
+
+ pgd = pgd_offset(mm, address);
+ if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+ goto no_page_table;
+
+ pud = pud_offset(pgd, address);
+ if (pud_none(*pud) || unlikely(pud_bad(*pud)))
+ goto no_page_table;
+
+ pmd = pmd_offset(pud, address);
+ if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
+ goto no_page_table;
+
+ /* We cannot handle huge page PFN maps. Luckily they don't exist. */
+ if (pmd_huge(*pmd))
+ goto no_page_table;
+
+ ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (!ptep)
+ goto out;
+
+ pte = *ptep;
+ if (!pte_present(pte))
+ goto unlock;
+ if ((flags & FOLL_WRITE) && !pte_write(pte))
+ goto unlock;
+ phys_addr = pte_pfn(pte);
+ phys_addr <<= PAGE_SHIFT; /* Shift here to avoid overflow on PAE */
+
+ *prot = pgprot_val(pte_pgprot(pte));
+
+unlock:
+ pte_unmap_unlock(ptep, ptl);
+out:
+ return phys_addr;
+no_page_table:
+ return 0;
+}
+
+int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+ void *buf, int len, int write)
+{
+ resource_size_t phys_addr;
+ unsigned long prot = 0;
+ void *maddr;
+ int offset = addr & (PAGE_SIZE-1);
+
+ if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+ return -EINVAL;
+
+ phys_addr = follow_phys(vma, addr, write, &prot);
+
+ if (!phys_addr)
+ return -EINVAL;
+
+ maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
+ if (write)
+ memcpy_toio(maddr + offset, buf, len);
+ else
+ memcpy_fromio(buf, maddr + offset, len);
+ iounmap(maddr);
+
+ return len;
+}
+#endif
+
/*
* Access another process' address space.
* Source/target buffer must be kernel space,
@@ -2760,7 +2840,6 @@
{
struct mm_struct *mm;
struct vm_area_struct *vma;
- struct page *page;
void *old_buf = buf;
mm = get_task_mm(tsk);
@@ -2772,28 +2851,44 @@
while (len) {
int bytes, ret, offset;
void *maddr;
+ struct page *page = NULL;
ret = get_user_pages(tsk, mm, addr, 1,
write, 1, &page, &vma);
- if (ret <= 0)
- break;
-
- bytes = len;
- offset = addr & (PAGE_SIZE-1);
- if (bytes > PAGE_SIZE-offset)
- bytes = PAGE_SIZE-offset;
-
- maddr = kmap(page);
- if (write) {
- copy_to_user_page(vma, page, addr,
- maddr + offset, buf, bytes);
- set_page_dirty_lock(page);
+ if (ret <= 0) {
+ /*
+ * Check if this is a VM_IO | VM_PFNMAP VMA, which
+ * we can access using slightly different code.
+ */
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+ vma = find_vma(mm, addr);
+ if (!vma)
+ break;
+ if (vma->vm_ops && vma->vm_ops->access)
+ ret = vma->vm_ops->access(vma, addr, buf,
+ len, write);
+ if (ret <= 0)
+#endif
+ break;
+ bytes = ret;
} else {
- copy_from_user_page(vma, page, addr,
- buf, maddr + offset, bytes);
+ bytes = len;
+ offset = addr & (PAGE_SIZE-1);
+ if (bytes > PAGE_SIZE-offset)
+ bytes = PAGE_SIZE-offset;
+
+ maddr = kmap(page);
+ if (write) {
+ copy_to_user_page(vma, page, addr,
+ maddr + offset, buf, bytes);
+ set_page_dirty_lock(page);
+ } else {
+ copy_from_user_page(vma, page, addr,
+ buf, maddr + offset, bytes);
+ }
+ kunmap(page);
+ page_cache_release(page);
}
- kunmap(page);
- page_cache_release(page);
len -= bytes;
buf += bytes;
addr += bytes;
