Commit 17e8de7e authored Aug 22, 2013 by Tom Musta Committed by Benjamin Herrenschmidt Aug 27, 2013

powerpc: Unaligned stores and stmw are broken in emulation code



The stmw instruction was incorrectly decoded as an update form instruction
and thus the RA register was being clobbered.

Also, the utility routine to write memory to unaligned addresses breaks the
operation into smaller aligned accesses but was incorrectly incrementing
the address by only one; it needs to increment the address by the size of
the smaller aligned chunk.

Signed-off-by: Tom Musta <tmusta@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent f748edaf

arch/powerpc/lib/sstep.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -100,9 +100,11 @@ static unsigned long __kprobes dform_ea(unsigned int instr, struct pt_regs *regs
		ea = (signed short) instr; /* sign-extend */
		if (ra) {
		ea += regs->gpr[ra];
		if (instr & 0x04000000) /* update forms */
		if (instr & 0x04000000) { /* update forms */
		if ((instr>>26) != 47) /* stmw is not an update form */
		regs->gpr[ra] = ea;
		}
		}

		return truncate_if_32bit(regs->msr, ea);
		}
		@@ -279,7 +281,7 @@ static int __kprobes write_mem_unaligned(unsigned long val, unsigned long ea,
		err = write_mem_aligned(val >> (nb - c) * 8, ea, c);
		if (err)
		return err;
		++ea;
		ea += c;
		}
		return 0;
		}