On Fri, May 26, 2023 at 07:54:17PM +0100, Greg KH wrote:
On Mon, May 22, 2023 at 10:33:44PM +0200, Jiri Olsa wrote:
hi, we see broken access to user space with bpf_probe_read/bpf_probe_read_str helpers on arm64 with 5.4 kernel. The problem is that both helpers try to read user memory by calling probe_kernel_read, which seems to work on x86 but fails on arm64.
Has this ever worked on arm64 for the 5.4 kernel tree? If not, it's not really a regression, and so, why not use a newer kernel that has this new feature added to it there?
In other words, what requires you to use the 5.4.y tree and requires feature parity across architectures?
we have a customer running ok on x86 v5.4, but arm64 is broken with the same bpf/user space code
upgrade is an option of course, but it's not a big change and we can have 5.4 working on arm64 as well
I can send out the change that will be closer to upstream changes, if that's a concern.. with adding the new probe helpers, which I guess is not a problem, because it does not change current API
jirka