Re: [U-Boot] [PATCH] 8313erdb: Set guarded bit on BAT that covers the end of the address space.

On Tuesday 17 March 2009 13:09:31 Scott Wood wrote:

This board currently sets DBAT6 to cover all of the final 256MiB of address space; however, not all of this space is covered by a device. In particular, flash sits at 0xfe000000-0xfe7fffff, and nothing is mapped at the far end of the address space.

In zlib, there is a loop that references p[-1] if p is non-NULL. Under some circumstances, this leads to the CPU speculatively loading from 0xfffffff8 if p is NULL. This leads to a machine check.

isnt that a compiler generating bad code then ? if C code is doing ptr checks, the compiler should make sure that pointer is not dereferenced at all if the hardware cannot suffer the consequences, even speculatively. -mike