On 2024/3/5 10:54, Jiangfeng Xiao wrote: > > > On 2024/3/4 23:15, Jann Horn wrote: >> On Mon, Mar 4, 2024 at 3:02 AM Jiangfeng Xiao <xiaojiangfeng@xxxxxxxxxx> wrote: >>> When the last instruction of a noreturn function is a call >>> to another function, the return address falls outside >>> of the function boundary. This seems to cause kernel >>> to interrupt the backtrace. >> [...] >>> Delete __noreturn from usercopy_abort, >> >> This sounds like the actual bug is in the backtracing logic? I don't >> think removing __noreturn annotations from an individual function is a >> good fix, since the same thing can happen with other __noreturn >> functions depending on what choices the compiler makes. >> . >> > Yes, you make a point. This may be a bug is in the backtracing logic, but > the kernel backtracing always parses symbols using (lr) instead of (lr-4). > This may be due to historical reasons or more comprehensive considerations. > In addition, modifying the implementation logic of the kernel backtracing > has a great impact. Therefore, I do not dare to modify the implementation > logic of the kernel backtracing. > > Not all noreturn functions are ended with calling other functions. > Therefore, only a few individual functions may have the same problem. > In addition, deleting '__noreturn' from usercopy_abort does not > change the internal behavior of usercopy_abort function. > Therefore, there is no risk. Deleting '__noreturn' from usercopy_abort > is the solution that I can think of with minimal impact and minimum risk. > > If you will submit a better patch to solve this problem, > I would like to learn from you. Thank you. > What are your suggestions on modifying the kernel backtracing logic or deleting '__noretrun'? If you insist on modifying the kernel backtracing logic and persuade me with good reasons, I can also try to submit the patch for modifying the kernel backtracing logic to the community.
