d0p1/ack - Cute Engineering : Cute solutions to hard problems

d0p1/ack

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Author	SHA1	Message	Date
George Koehler	1dfd5524e4	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.	2017-01-26 12:44:32 -05:00
David Given	8c3670483f	Get top working with the PowerPC; use it to eliminate useless branches and moves.	2016-10-29 23:37:11 +02:00
dtrg	4dd1ff6d80	Archival checkin (semi-working code).	2007-11-02 18:56:58 +00:00

Author

SHA1

Message

Date

George Koehler

1dfd5524e4

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.

2017-01-26 12:44:32 -05:00

David Given

8c3670483f

Get top working with the PowerPC; use it to eliminate useless branches and

moves.

2016-10-29 23:37:11 +02:00

dtrg

4dd1ff6d80

Archival checkin (semi-working code).

2007-11-02 18:56:58 +00:00

3 commits