From 1dfd5524e4c5691916a27e1fc5d84dd4b20e8c09 Mon Sep 17 00:00:00 2001 From: George Koehler Date: Thu, 26 Jan 2017 12:44:32 -0500 Subject: [PATCH] In PowerPC top, don't delete addi r0, r0, 0 Also don't delete addis r0, r0, 0. These instructions are special cases that set r0 to zero. If we delete them, then r0 keeps its old value. I caught this bug because osxppc protects the .text segment against writing. (linuxppc doesn't protect it.) A program tried to set r0 to the NULL pointer, but top deleted the instruction, so r0 kept an old return address pointing into .text. Later the program checked that r0 wasn't NULL, tried to write to address r0, and crashed. --- mach/powerpc/top/table | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mach/powerpc/top/table b/mach/powerpc/top/table index acbe543a7..fdec03b2e 100644 --- a/mach/powerpc/top/table +++ b/mach/powerpc/top/table @@ -6,15 +6,15 @@ LABEL_STARTER '.'; %%; -P, Q, R { TRUE }; +RNZ { strcmp(VAL, "r0") }; /* not r0 */ X, Y, Z { TRUE }; %%; /* Whitespace is significant here! */ -addi X, X, 0 -> ; -addis X, X, 0 -> ; +addi RNZ, RNZ, 0 -> ; +addis RNZ, RNZ, 0 -> ; mr X, X -> ; fmr X, X -> ;