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uprobes: Introduce copy_opcode(), kill read_opcode()

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No functional changes, preparations.

1. Extract the kmap-and-memcpy code from read_opcode() into the
   new trivial helper, copy_opcode(). The next patch will add
   another user.

2. read_opcode() becomes really trivial, fold it into its single
   caller, is_swbp_at_addr().

3. Remove "auprobe" argument from write_opcode(), it is not used
   since f403072c6.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-23 21:10:18 +02:00
parent e97f65a17d
commit cceb55aab7
1 changed files with 19 additions and 44 deletions
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63
kernel/events/uprobes.c
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@ -183,19 +183,25 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn)
return *insn == UPROBE_SWBP_INSN;
}
static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode)
{
void *kaddr = kmap_atomic(page);
memcpy(opcode, kaddr + (vaddr & ~PAGE_MASK), UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(kaddr);
}
/*
* NOTE:
* Expect the breakpoint instruction to be the smallest size instruction for
* the architecture. If an arch has variable length instruction and the
* breakpoint instruction is not of the smallest length instruction
* supported by that architecture then we need to modify read_opcode /
* supported by that architecture then we need to modify is_swbp_at_addr and
* write_opcode accordingly. This would never be a problem for archs that
* have fixed length instructions.
*/
/*
* write_opcode - write the opcode at a given virtual address.
* @auprobe: arch breakpointing information.
* @mm: the probed process address space.
* @vaddr: the virtual address to store the opcode.
* @opcode: opcode to be written at @vaddr.
@ -206,8 +212,8 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn)
* For mm @mm, write the opcode at @vaddr.
* Return 0 (success) or a negative errno.
*/
static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long vaddr, uprobe_opcode_t opcode)
static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
uprobe_opcode_t opcode)
{
struct page *old_page, *new_page;
void *vaddr_old, *vaddr_new;
@ -253,40 +259,9 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
return ret;
}
/**
* read_opcode - read the opcode at a given virtual address.
* @mm: the probed process address space.
* @vaddr: the virtual address to read the opcode.
* @opcode: location to store the read opcode.
*
* Called with mm->mmap_sem held (for read and with a reference to
* mm.
*
* For mm @mm, read the opcode at @vaddr and store it in @opcode.
* Return 0 (success) or a negative errno.
*/
static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode)
{
struct page *page;
void *vaddr_new;
int ret;
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (ret <= 0)
return ret;
vaddr_new = kmap_atomic(page);
vaddr &= ~PAGE_MASK;
memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(vaddr_new);
put_page(page);
return 0;
}
static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
struct page *page;
uprobe_opcode_t opcode;
int result;
@ -300,14 +275,14 @@ static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
goto out;
}
result = read_opcode(mm, vaddr, &opcode);
if (result)
result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (result < 0)
return result;
out:
if (is_swbp_insn(&opcode))
return 1;
return 0;
copy_opcode(page, vaddr, &opcode);
put_page(page);
out:
return is_swbp_insn(&opcode);
}
/**
@ -321,7 +296,7 @@ static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
*/
int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
return write_opcode(mm, vaddr, UPROBE_SWBP_INSN);
}
/**
@ -345,7 +320,7 @@ set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long v
if (result != 1)
return result;
return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
}
static int match_uprobe(struct uprobe *l, struct uprobe *r)