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@xxxxxxxxxxxxxxxxxx>
---
Changelog: (Since v5)
- Uprobes no more depends on MM_OWNER; No reference to task_structs
while inserting/removing a probe.
- Uses read_mapping_page instead of grab_cache_page so that the pages
have valid content.
include/linux/uprobes.h | 12 +++++
kernel/uprobes.c | 111 +++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 113 insertions(+), 10 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index b4de058..fa2b663 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 mm_struct *mm, struct uprobe *uprobe,
+ unsigned long vaddr);
+extern int __weak set_orig_insn(struct mm_struct *mm, 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 1baae40..f4574fd 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> /* read_mapping_page */
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/uprobes.h>
@@ -82,6 +83,20 @@ static bool valid_vma(struct vm_area_struct *vma, bool is_reg)
return false;
}
+int __weak set_bkpt(struct mm_struct *mm, struct uprobe *uprobe,
+ unsigned long vaddr)
+{
+ /* placeholder: yet to be implemented */
+ return 0;
+}
+
+int __weak set_orig_insn(struct mm_struct *mm, 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)
{
if (l->inode < r->inode)
@@ -251,8 +266,71 @@ static bool del_consumer(struct uprobe *uprobe,
return ret;
}
-static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe)
+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 = read_mapping_page(mapping, idx, filp);
+ if (IS_ERR(page))
+ return -ENOMEM;
+
+ vaddr = kmap_atomic(page);
+ memcpy(insn, vaddr + off1, nbytes);
+ kunmap_atomic(vaddr);
+ 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 int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe,
+ struct vm_area_struct *vma, loff_t vaddr)
{
+ unsigned long addr;
+ int ret = -EINVAL;
+
/*
* Probe is to be deleted;
* Dont know if somebody already inserted the probe;
@@ -261,15 +339,27 @@ static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe)
if (!uprobe->consumers)
return -EEXIST;
- atomic_inc(&mm->mm_uprobes_count);
- return 0;
+ addr = (unsigned long)vaddr;
+ if (!uprobe->copy) {
+ ret = copy_insn(uprobe, vma, addr);
+ if (ret)
+ return ret;
+
+ /* TODO : Analysis and verification of instruction */
+ uprobe->copy = 1;
+ }
+ ret = set_bkpt(mm, uprobe, addr);
+ if (!ret)
+ atomic_inc(&mm->mm_uprobes_count);
+
+ 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;
+ if (!set_orig_insn(mm, uprobe, (unsigned long)vaddr, true))
+ atomic_dec(&mm->mm_uprobes_count);
}
static void delete_uprobe(struct uprobe *uprobe)
@@ -385,7 +475,7 @@ 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);
up_read(&mm->mmap_sem);
mmput(mm);
if (ret && ret == -EEXIST)
@@ -436,7 +526,7 @@ 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);
}
@@ -627,7 +717,8 @@ int mmap_uprobe(struct vm_area_struct *vma)
put_uprobe(uprobe);
continue;
}
- ret = install_breakpoint(vma->vm_mm, uprobe);
+ ret = install_breakpoint(vma->vm_mm, uprobe, vma,
+ vaddr);
if (ret == -EEXIST) {
atomic_inc(&vma->vm_mm->mm_uprobes_count);
ret = 0;
--
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