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uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp() 

If handle_swbp()->add_utask() fails but UPROBE_SKIP_SSTEP is set,
cleanup_ret: path do not restart the insn, this is wrong. Remove
this check and add the additional label for can_skip_sstep() = T
case.

Note also that UPROBE_SKIP_SSTEP can be false positive, we simply
can not trust it unless arch_uprobe_skip_sstep() was already called.

Also, move another UPROBE_SKIP_SSTEP check before can_skip_sstep()
into this helper, this looks more clean and understandable.

Note: probably we should rename "skip" to "emulate" and I think
that "clear UPROBE_SKIP_SSTEP" should be moved to arch_can_skip.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-14 18:31:23 +02:00
parent 746a9e6ba2
commit 0578a97098
1 changed files with 15 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
kernel/events/uprobes.c
View File

@ -1389,10 +1389,11 @@ bool uprobe_deny_signal(void)
*/
static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
{
if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
return true;
uprobe->flags &= ~UPROBE_SKIP_SSTEP;
if (uprobe->flags & UPROBE_SKIP_SSTEP) {
if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
return true;
uprobe->flags &= ~UPROBE_SKIP_SSTEP;
}
return false;
}
@ -1494,12 +1495,12 @@ static void handle_swbp(struct pt_regs *regs)
utask = add_utask();
/* Cannot allocate; re-execute the instruction. */
if (!utask)
goto cleanup_ret;
goto restart;
}
handler_chain(uprobe, regs);
if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
goto cleanup_ret;
if (can_skip_sstep(uprobe, regs))
goto out;
if (!pre_ssout(uprobe, regs, bp_vaddr)) {
arch_uprobe_enable_step(&uprobe->arch);
@ -1508,15 +1509,13 @@ static void handle_swbp(struct pt_regs *regs)
return;
}
cleanup_ret:
if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
/*
* cannot singlestep; cannot skip instruction;
* re-execute the instruction.
*/
instruction_pointer_set(regs, bp_vaddr);
restart:
/*
* cannot singlestep; cannot skip instruction;
* re-execute the instruction.
*/
instruction_pointer_set(regs, bp_vaddr);
out:
put_uprobe(uprobe);
}