Re: CET/IBT support and live-patches

On Wed, Dec 01, 2021 at 01:57:00PM -0500, Joe Lawrence wrote:

On 11/23/21 4:16 PM, Peter Zijlstra wrote:

quoted

On Tue, Nov 23, 2021 at 03:58:51PM -0500, Joe Lawrence wrote:

quoted

Yep, kpatch-build uses its own klp-relocation conversion and not kallsyms.

I'm not familiar with CET/IBT, but it sounds like if a function pointer
is not taken at build time (or maybe some other annotation), the
compiler won't generate the needed endbr landing spot in said function?

Currently it does, but then I'm having objtool scribble it on purpose.

Hi Peter -- to follow up on the objtool part: what criteria is used to
determine that it may scribble out the endbr?

ENDBR is "scribbled" for any function for which no function pointer data
relocation exists at vmlinux or module link time.

https://lkml.kernel.org/r/20211122170301.764232470@infradead.org

-- 
Josh