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Subject[PATCH v5 3.1.0-rc4-tip 5/26] Uprobes: copy of the original instruction.

When inserting the first probepoint, save a copy of the original
instruction. This copy is later used for fixup analysis, copied to the slot
on probe-hit and for restoring the original instruction.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
arch/Kconfig | 1
include/linux/uprobes.h | 12 ++++
kernel/uprobes.c | 142 +++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 143 insertions(+), 12 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index dedd489..d6a4e1d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -63,6 +63,7 @@ config OPTPROBES

config UPROBES
bool "User-space probes (EXPERIMENTAL)"
+ select MM_OWNER
help
Uprobes enables kernel subsystems to establish probepoints
in user applications and execute handler functions when
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index b4de058..50a8c67 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -26,6 +26,12 @@
#include <linux/rbtree.h>

struct vm_area_struct;
+#ifdef CONFIG_ARCH_SUPPORTS_UPROBES
+#include <asm/uprobes.h>
+#else
+
+#define MAX_UINSN_BYTES 4
+#endif

struct uprobe_consumer {
int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
@@ -46,9 +52,15 @@ struct uprobe {
struct uprobe_consumer *consumers;
struct inode *inode; /* Also hold a ref to inode */
loff_t offset;
+ int copy;
+ u8 insn[MAX_UINSN_BYTES];
};

#ifdef CONFIG_UPROBES
+extern int __weak set_bkpt(struct task_struct *tsk, struct uprobe *uprobe,
+ unsigned long vaddr);
+extern int __weak set_orig_insn(struct task_struct *tsk,
+ struct uprobe *uprobe, unsigned long vaddr, bool verify);
extern int register_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer);
extern void unregister_uprobe(struct inode *inode, loff_t offset,
diff --git a/kernel/uprobes.c b/kernel/uprobes.c
index 5bc3f90..e0e10dd 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -23,6 +23,7 @@

#include <linux/kernel.h>
#include <linux/highmem.h>
+#include <linux/pagemap.h> /* grab_cache_page */
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/uprobes.h>
@@ -59,6 +60,20 @@ static bool valid_vma(struct vm_area_struct *vma)
return false;
}

+int __weak set_bkpt(struct task_struct *tsk, struct uprobe *uprobe,
+ unsigned long vaddr)
+{
+ /* placeholder: yet to be implemented */
+ return 0;
+}
+
+int __weak set_orig_insn(struct task_struct *tsk, struct uprobe *uprobe,
+ unsigned long vaddr, bool verify)
+{
+ /* placeholder: yet to be implemented */
+ return 0;
+}
+
static int match_uprobe(struct uprobe *l, struct uprobe *r, int *match_inode)
{
/*
@@ -248,22 +263,125 @@ static bool del_consumer(struct uprobe *uprobe,
return ret;
}

+static int __copy_insn(struct address_space *mapping,
+ struct vm_area_struct *vma, char *insn,
+ unsigned long nbytes, unsigned long offset)
+{
+ struct file *filp = vma->vm_file;
+ struct page *page;
+ void *vaddr;
+ unsigned long off1;
+ unsigned long idx;
+
+ if (!filp)
+ return -EINVAL;
+
+ idx = (unsigned long) (offset >> PAGE_CACHE_SHIFT);
+ off1 = offset &= ~PAGE_MASK;
+
+ /*
+ * Ensure that the page that has the original instruction is
+ * populated and in page-cache.
+ */
+ page_cache_sync_readahead(mapping, &filp->f_ra, filp, idx, 1);
+ page = grab_cache_page(mapping, idx);
+ if (!page)
+ return -ENOMEM;
+
+ vaddr = kmap_atomic(page);
+ memcpy(insn, vaddr + off1, nbytes);
+ kunmap_atomic(vaddr);
+ unlock_page(page);
+ page_cache_release(page);
+ return 0;
+}
+
+static int copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ struct address_space *mapping;
+ int bytes;
+ unsigned long nbytes;
+
+ addr &= ~PAGE_MASK;
+ nbytes = PAGE_SIZE - addr;
+ mapping = uprobe->inode->i_mapping;
+
+ /* Instruction at end of binary; copy only available bytes */
+ if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
+ bytes = uprobe->inode->i_size - uprobe->offset;
+ else
+ bytes = MAX_UINSN_BYTES;
+
+ /* Instruction at the page-boundary; copy bytes in second page */
+ if (nbytes < bytes) {
+ if (__copy_insn(mapping, vma, uprobe->insn + nbytes,
+ bytes - nbytes, uprobe->offset + nbytes))
+ return -ENOMEM;
+ bytes = nbytes;
+ }
+ return __copy_insn(mapping, vma, uprobe->insn, bytes, uprobe->offset);
+}
+
+static struct task_struct *get_mm_owner(struct mm_struct *mm)
+{
+ struct task_struct *tsk;
+
+ rcu_read_lock();
+ tsk = rcu_dereference(mm->owner);
+ if (tsk)
+ get_task_struct(tsk);
+ rcu_read_unlock();
+ return tsk;
+}

-static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe)
+static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe,
+ struct vm_area_struct *vma, loff_t vaddr)
{
- /* Placeholder: Yet to be implemented */
+ struct task_struct *tsk;
+ unsigned long addr;
+ int ret = -EINVAL;
+
if (!uprobe->consumers)
return 0;

- atomic_inc(&mm->mm_uprobes_count);
- return 0;
+ tsk = get_mm_owner(mm);
+ if (!tsk) /* task is probably exiting; bail-out */
+ return -ESRCH;
+
+ if (vaddr > TASK_SIZE_OF(tsk))
+ goto put_return;
+
+ addr = (unsigned long) vaddr;
+ if (!uprobe->copy) {
+ ret = copy_insn(uprobe, vma, addr);
+ if (ret)
+ goto put_return;
+ /* TODO : Analysis and verification of instruction */
+ uprobe->copy = 1;
+ }
+
+ ret = set_bkpt(tsk, uprobe, addr);
+ if (!ret)
+ atomic_inc(&mm->mm_uprobes_count);
+
+put_return:
+ put_task_struct(tsk);
+ return ret;
}

-static void remove_breakpoint(struct mm_struct *mm, struct uprobe *uprobe)
+static void remove_breakpoint(struct mm_struct *mm, struct uprobe *uprobe,
+ loff_t vaddr)
{
- /* Placeholder: Yet to be implemented */
- atomic_dec(&mm->mm_uprobes_count);
- return;
+ struct task_struct *tsk = get_mm_owner(mm);
+
+ if (!tsk) /* task is probably exiting; bail-out */
+ return;
+
+ if (!set_orig_insn(tsk, uprobe, (unsigned long) vaddr, true))
+ atomic_dec(&mm->mm_uprobes_count);
+
+ put_task_struct(tsk);
}

static void delete_uprobe(struct uprobe *uprobe)
@@ -362,7 +480,7 @@ static int __register_uprobe(struct inode *inode, loff_t offset,
mmput(mm);
continue;
}
- ret = install_breakpoint(mm, uprobe);
+ ret = install_breakpoint(mm, uprobe, vma, vi->vaddr);
if (ret && (ret != -ESRCH || ret != -EEXIST)) {
up_read(&mm->mmap_sem);
mmput(mm);
@@ -404,7 +522,7 @@ static void __unregister_uprobe(struct inode *inode, loff_t offset,
mmput(mm);
continue;
}
- remove_breakpoint(mm, uprobe);
+ remove_breakpoint(mm, uprobe, vi->vaddr);
up_read(&mm->mmap_sem);
mmput(mm);
}
@@ -564,8 +682,8 @@ int mmap_uprobe(struct vm_area_struct *vma)
vaddr -= vma->vm_pgoff << PAGE_SHIFT;
if (vaddr < vma->vm_start || vaddr >= vma->vm_end)
continue;
- ret = install_breakpoint(vma->vm_mm, uprobe);
-
+ ret = install_breakpoint(vma->vm_mm, uprobe, vma,
+ vaddr);
if (ret && (ret == -ESRCH || ret == -EEXIST))
ret = 0;
}

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