Hey Thomas Here is my feedback for your outstanding constification patches [1] and [2]. # You need to split the patch The answer that you got from Jakub in the network subsystem is very clear and baring a change of heart from the network folks, this will go in as but as a split patchset. Please split it considering the following: 1. Create a different patchset for drivers/, fs/, kernel/, net, and a miscellaneous that includes whatever does not fit into the others. 2. Consider that this might take several releases. 3. Consider the following sufix for the interim function name "_const". Like in kfree_const. Please not "_new". 4. Please publish the final result somewhere. This is important so someone can take over in case you need to stop. 5. Consistently mention the motivation in your cover letters. I specify more further down in "#Motivation". 6. Also mention that this is part of a bigger effort (like you did in your original cover letters). I would include [3,4,5,6] 7. Include a way to show what made it into .rodata. I specify more further down in "#Show the move". # Motivation As I read it, the motivation for these constification efforts are: 1. It provides increased safety: Having things in .rodata section reduces the attack surface. This is especially relevant for structures that have function pointers (like ctl_table); having these in .rodata means that these pointers always point to the "intended" function and cannot be changed. 2. Compiler optimizations: This was just a comment in the patchsets that I have mentioned ([3,4,5]). Do you know what optimizations specifically? Does it have to do with enhancing locality for the data in .rodata? Do you have other specific optimizations in mind? 3. Readability: because it is easier to know up-front that data is not supposed to change or its obvious that a function is re-entrant. Actually a lot of the readability reasons is about knowing things "up-front". As we move forward with the constification in sysctl, please include a more detailed motivation in all your cover letters. This helps maintainers (that don't have the context) understand what you are trying to do. It does not need to be my three points, but it should be more than just "put things into .rodata". Please tell me if I have missed anything in the motivation. # Show the move I created [8] because there is no easy way to validate which objects made it into .rodata. I ran [8] for your Dec 2nd patcheset [7] and there are less in .rodata than I expected (the results are in [9]) Why is that? Is it something that has not been posted to the lists yet? Best [1] https://lore.kernel.org/all/20240423-sysctl-const-handler-v3-0-e0beccb836e2@xxxxxxxxxxxxxx/ [2] https://lore.kernel.org/all/20240418-sysctl-const-table-arg-v2-1-4012abc31311@xxxxxxxxxxxxxx [3] [PATCH v2 00/14] ASoC: Constify local snd_sof_dsp_ops https://lore.kernel.org/all/20240426-n-const-ops-var-v2-0-e553fe67ae82@xxxxxxxxxx [4] [PATCH v2 00/19] backlight: Constify lcd_ops https://lore.kernel.org/all/20240424-video-backlight-lcd-ops-v2-0-1aaa82b07bc6@xxxxxxxxxx [5] [PATCH 1/4] iommu: constify pointer to bus_type https://lore.kernel.org/all/20240216144027.185959-1-krzysztof.kozlowski@xxxxxxxxxx [6] [PATCH 00/29] const xattr tables https://lore.kernel.org/all/20230930050033.41174-1-wedsonaf@xxxxxxxxx [7] https://lore.kernel.org/all/20231204-const-sysctl-v2-0-7a5060b11447@xxxxxxxxxxxxxx/ [8] #!/usr/bin/python3 import subprocess import re def exec_cmd( cmd ): try: result = subprocess.run(cmd, shell=True, text=True, check=True, capture_output=True) output_lines = result.stdout.splitlines() return output_lines except Exception as e: print(f"An error occurred: {e}") return [] def remove_tokens_re(lines, regex_patterns, uniq = True): filtered_lines = [] seen_lines = set() regexes = [re.compile(pattern) for pattern in regex_patterns] for line in lines: for regex in regexes: line = regex.sub('', line) # Replace matches with empty string if uniq: if line not in seen_lines: seen_lines.add(line) filtered_lines.append(line) else: filtered_lines.append(line) return filtered_lines def filter_in_lines(lines, regex_patterns): filtered_lines = [] regexes = [re.compile(pattern) for pattern in regex_patterns] for line in lines: if any(regex.search(line) for regex in regexes): filtered_lines.append(line) return filtered_lines cmd = "git grep 'static \(const \)\?struct ctl_table '" regex_patterns = ['[\}]*;$', ' = \{', '\[.*\]', '.*\.(c|h):[ \t]*static (const )?struct ctl_table '] ctl_table_structs = remove_tokens_re(exec_cmd( cmd ), regex_patterns) cmd = "readelf -X -Ws build/vmlinux" regex_patterns = ['.*OBJECT.*'] output_lines = filter_in_lines(exec_cmd( cmd ), regex_patterns); regex_patterns = ['^.*OBJECT', '[ \t]+[A-Z]+[ \t]+[A-Z]+.*\(.*\)[ \t]+'] obj_elems = remove_tokens_re( output_lines, regex_patterns, uniq=False) regex_patterns = ['^.*\(', '\)[ ]+.*$'] sec_names = remove_tokens_re( output_lines, regex_patterns, uniq=False) for i in range(len(sec_names)): obj_name = obj_elems[i] if obj_name in ctl_table_structs: print ("section: {}\t\tobj_name : {}". format(sec_names[i], obj_name)) [9] section: .rodata obj_name : kern_table section: .rodata obj_name : sysctl_mount_point section: .rodata obj_name : addrconf_sysctl section: .rodata obj_name : ax25_param_table section: .rodata obj_name : mpls_table section: .rodata obj_name : mpls_dev_table section: .data obj_name : sld_sysctls section: .data obj_name : kern_panic_table section: .data obj_name : kern_exit_table section: .data obj_name : vm_table section: .data obj_name : signal_debug_table section: .data obj_name : usermodehelper_table section: .data obj_name : kern_reboot_table section: .data obj_name : user_table section: .bss obj_name : sched_core_sysctls section: .data obj_name : sched_fair_sysctls section: .data obj_name : sched_rt_sysctls section: .data obj_name : sched_dl_sysctls section: .data obj_name : printk_sysctls section: .data obj_name : pid_ns_ctl_table_vm section: .data obj_name : seccomp_sysctl_table section: .data obj_name : uts_kern_table section: .data obj_name : vm_oom_kill_table section: .data obj_name : vm_page_writeback_sysctls section: .data obj_name : page_alloc_sysctl_table section: .data obj_name : hugetlb_table section: .data obj_name : fs_stat_sysctls section: .data obj_name : fs_exec_sysctls section: .data obj_name : fs_pipe_sysctls section: .data obj_name : namei_sysctls section: .data obj_name : fs_dcache_sysctls section: .data obj_name : inodes_sysctls section: .data obj_name : fs_namespace_sysctls section: .data obj_name : dnotify_sysctls section: .data obj_name : inotify_table section: .data obj_name : epoll_table section: .data obj_name : aio_sysctls section: .data obj_name : locks_sysctls section: .data obj_name : coredump_sysctls section: .data obj_name : fs_shared_sysctls section: .data obj_name : fs_dqstats_table section: .data obj_name : root_table section: .data obj_name : pty_table section: .data obj_name : xfs_table section: .data obj_name : ipc_sysctls section: .data obj_name : key_sysctls section: .data obj_name : kernel_io_uring_disabled_table section: .data obj_name : tty_table section: .data obj_name : random_table section: .data obj_name : scsi_table section: .data obj_name : iwcm_ctl_table section: .data obj_name : net_core_table section: .data obj_name : netns_core_table section: .bss obj_name : nf_log_sysctl_table section: .data obj_name : nf_log_sysctl_ftable section: .data obj_name : vs_vars section: .data obj_name : vs_vars_table section: .data obj_name : ipv4_route_netns_table section: .data obj_name : ipv4_route_table section: .data obj_name : ip4_frags_ns_ctl_table section: .data obj_name : ip4_frags_ctl_table section: .data obj_name : ctl_forward_entry section: .data obj_name : ipv4_table section: .data obj_name : ipv4_net_table section: .data obj_name : unix_table section: .data obj_name : ipv6_route_table_template section: .data obj_name : ipv6_icmp_table_template section: .data obj_name : ip6_frags_ns_ctl_table section: .data obj_name : ip6_frags_ctl_table section: .data obj_name : ipv6_table_template section: .data obj_name : ipv6_rotable section: .data obj_name : sctp_net_table section: .data obj_name : sctp_table section: .data obj_name : smc_table section: .data obj_name : lowpan_frags_ns_ctl_table section: .data obj_name : lowpan_frags_ctl_table -- Joel Granados
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