powerpc/watchpoint: Fix length calculation for unaligned target

Watchpoint match range is always doubleword(8 bytes) aligned on
powerpc. If the given range is crossing doubleword boundary, we need
to increase the length such that next doubleword also get
covered. Ex,

          address   len = 6 bytes
                |=========.
   |------------v--|------v--------|
   | | | | | | | | | | | | | | | | |
   |---------------|---------------|
    <---8 bytes--->

In such case, current code configures hw as:
  start_addr = address & ~HW_BREAKPOINT_ALIGN
  len = 8 bytes

And thus read/write in last 4 bytes of the given range is ignored.
Fix this by including next doubleword in the length.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191017093204.7511-3-ravi.bangoria@linux.ibm.com

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h
index 4a887e85a5f4..ea91ac7f5a27 100644
--- a/arch/powerpc/include/asm/hw_breakpoint.h
+++ b/arch/powerpc/include/asm/hw_breakpoint.h
@@ -14,6 +14,7 @@ struct arch_hw_breakpoint {
 	unsigned long	address;
 	u16		type;
 	u16		len; /* length of the target data symbol */
+	u16		hw_len; /* length programmed in hw */
 };
 
 /* Note: Don't change the the first 6 bits below as they are in the same order
@@ -73,6 +74,7 @@ static inline void hw_breakpoint_disable(void)
 	brk.address = 0;
 	brk.type = 0;
 	brk.len = 0;
+	brk.hw_len = 0;
 	if (ppc_breakpoint_available())
 		__set_breakpoint(&brk);
 }