• Frederic Weisbecker's avatar
    hw-breakpoints: Change/Enforce some breakpoints policies · b2812d03
    Frederic Weisbecker authored
    The current policies of breakpoints in x86 and SH are the following:
    
    - task bound breakpoints can only break on userspace addresses
    - cpu wide breakpoints can only break on kernel addresses
    
    The former rule prevents ptrace breakpoints to be set to trigger on
    kernel addresses, which is good. But as a side effect, we can't
    breakpoint on kernel addresses for task bound breakpoints.
    
    The latter rule simply makes no sense, there is no reason why we
    can't set breakpoints on userspace while performing cpu bound
    profiles.
    
    We want the following new policies:
    
    - task bound breakpoint can set userspace address breakpoints, with
    no particular privilege required.
    - task bound breakpoints can set kernelspace address breakpoints but
    must be privileged to do that.
    - cpu bound breakpoints can do what they want as they are privileged
    already.
    
    To implement these new policies, this patch checks if we are dealing
    with a kernel address breakpoint, if so and if the exclude_kernel
    parameter is set, we tell the user that the breakpoint is invalid,
    which makes a good generic ptrace protection.
    If we don't have exclude_kernel, ensure the user has the right
    privileges as kernel breakpoints are quite sensitive (risk of
    trap recursion attacks and global performance impacts).
    
    [ Paul Mundt: keep addr space check for sh signal delivery and fix
      double function declaration]
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
    Cc: K. Prasad <prasad@linux.vnet.ibm.com>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Jason Wessel <jason.wessel@windriver.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
    b2812d03
hw_breakpoint.c 11.5 KB