Given the legacy bpf_probe_read{,str}() BPF helpers are broken on archs with overlapping address ranges, we should really take the next step to disable them from BPF use there. To generally fix the situation, we've recently added new helper variants bpf_probe_read_{user,kernel}() and bpf_probe_read_{user,kernel}_str(). For details on them, see 6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user,kernel}_str helpers"). Given bpf_probe_read{,str}() have been around for ~5 years by now, there are plenty of users at least on x86 still relying on them today, so we cannot remove them entirely w/o breaking the BPF tracing ecosystem. However, their use should be restricted to archs with non-overlapping address ranges where they are working in their current form. Therefore, move this behind a CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE and have x86, arm64, arm select it (other archs supporting it can follow-up on it as well). For the remaining archs, they can workaround easily by relying on the feature probe from bpftool which spills out defines that can be used out of BPF C code to implement the drop-in replacement for old/new kernels via: bpftool feature probe macro
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| @@ -825,14 +825,16 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) · 824 unmodified lines | |||
| 825 | return &bpf_probe_read_user_proto; | 825 | return &bpf_probe_read_user_proto; |
| 826 | case BPF_FUNC_probe_read_kernel: | 826 | case BPF_FUNC_probe_read_kernel: |
| 827 | return &bpf_probe_read_kernel_proto; | 827 | return &bpf_probe_read_kernel_proto; |
| 828 | case BPF_FUNC_probe_read: | ||
| 829 | return &bpf_probe_read_compat_proto; | ||
| 830 | case BPF_FUNC_probe_read_user_str: | 828 | case BPF_FUNC_probe_read_user_str: |
| 831 | return &bpf_probe_read_user_str_proto; | 829 | return &bpf_probe_read_user_str_proto; |
| 832 | case BPF_FUNC_probe_read_kernel_str: | 830 | case BPF_FUNC_probe_read_kernel_str: |
| 833 | return &bpf_probe_read_kernel_str_proto; | 831 | return &bpf_probe_read_kernel_str_proto; |
| 832 | #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE | ||
| 833 | case BPF_FUNC_probe_read: | ||
| 834 | return &bpf_probe_read_compat_proto; | ||
| 834 | case BPF_FUNC_probe_read_str: | 835 | case BPF_FUNC_probe_read_str: |
| 835 | return &bpf_probe_read_compat_str_proto; | 836 | return &bpf_probe_read_compat_str_proto; |
| 837 | #endif | ||
| 836 | #ifdef CONFIG_CGROUPS | 838 | #ifdef CONFIG_CGROUPS |
| 837 | case BPF_FUNC_get_current_cgroup_id: | 839 | case BPF_FUNC_get_current_cgroup_id: |
| 838 | return &bpf_get_current_cgroup_id_proto; | 840 | return &bpf_get_current_cgroup_id_proto; |