powerpc/hw_brk: Fix setting of length for exact mode breakpoints

commit b0b0aa9c7faf94e92320eabd8a1786c7747e40a8 upstream.

The smallest match region for both the DABR and DAWR is 8 bytes, so the
kernel needs to filter matches when users want to look at regions smaller than
this.

Currently we set the length of PPC_BREAKPOINT_MODE_EXACT breakpoints to 8.
This is wrong as in exact mode we should only match on 1 address, hence the
length should be 1.

This ensures that the kernel will filter out any exact mode hardware breakpoint
matches on any addresses other than the requested one.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Reported-by: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 98c2fc198712..64f7bd5b1b0f 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -1449,7 +1449,9 @@ static long ppc_set_hwdebug(struct task_struct *child,
          */
         if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE) {
                 len = bp_info->addr2 - bp_info->addr;
-        } else if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT) {
+        } else if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_EXACT)
+                len = 1;
+        else {
                 ptrace_put_breakpoints(child);
                 return -EINVAL;
         }