From: Arnd Bergmann <email@example.com> To: "Eric W. Biederman" <firstname.lastname@example.org> Cc: Geoff Levand <email@example.com>, Linus Torvalds <firstname.lastname@example.org>, Oleg Nesterov <email@example.com>, Linux Kernel Mailing List <firstname.lastname@example.org>, linux-fsdevel <email@example.com>, Alexander Viro <firstname.lastname@example.org>, Michael Ellerman <email@example.com>, Arnd Bergmann <firstname.lastname@example.org> Subject: Re: [PATCH v2 02/24] exec: Simplify unshare_files Date: Fri, 27 Nov 2020 21:29:33 +0100 [thread overview] Message-ID: <CAK8P3a0hPG1cTxksTBCJHkAV_=TLZLCi2pZYMk2Dc2-kLzD3rg@mail.gmail.com> (raw) In-Reply-To: <email@example.com> On Wed, Nov 25, 2020 at 2:16 AM Eric W. Biederman <firstname.lastname@example.org> wrote: > > On 11/24/20 12:14 PM, Arnd Bergmann wrote: > > > > There are still PS3-Linux users out there. They use 'Homebrew' firmware > > released through 'Hacker' forums that allow them to run Linux on > > non-supported systems. They are generally hobbies who don't post to > > Linux kernel mailing lists. I get direct inquiries regularly asking > > about how to update to a recent kernel. One of the things that attract > > them to the PS3 is the Cell processor and either using or programming > > the SPUs. > > > > It is difficult to judge how much use the SPU core dump support gets, > > but if it is not a cause of major problems I feel we should consider > > keeping it. > > I just took a quick look to get a sense how much tool support there is. > > In the gdb tree I found this 2019 commit abf516c6931a ("Remove Cell > Broadband Engine debugging support"). Which basically removes the code > in gdb that made sense of the spu coredumps. Ah, I had not realized this was gone already. The code in gdb for seamlessly debugging programs across CPU and SPU was clearly more complex than the kernel portion for the coredump, so it makes sense this was removed eventually. > I would not say the coredump support is a source major problems, but it > is a challenge to understand. One of the pieces of code in there that > is necessary to make the coredump support work reliable, a call to > unshare_files, Oleg whole essentially maintains the ptrace and coredump > support did not know why it was there, and it was not at all obvious > when I looked at the code. > > So we are certainly in maintainers loosing hours of time figuring out > what is going on and spending time fixing fuzzer bugs related to the > code. I also spent some amount of time on this code earlier this year Christoph did some refactoring, and we could both have used that time better. > At the minimum I will add a few more comments so people reading the code > can realize why it is there. Perhaps putting the relevant code behind > a Kconfig so it is only built into the kernel when spufs is present. > > I think we are at a point we we can start planning on removing the > coredump support. The tools to read it are going away. None of what is > there is bad, but it is definitely a special case, and it definitely has > a maintenance cost. How about adding a comment in the coredump code so it can get removed the next time someone comes across it during refactoring, or when they find a bug that can't easily be worked around? That way there is still a chance of using it where needed, but hopefully it won't waste anyone's time when it gets in the way. If there are no objections, I can also send a patch to remove CONFIG_PPC_CELL_NATIVE, PPC_IBM_CELL_BLADE and everything that depends on those symbols, leaving only the bits needed by ps3 in the arch/powerpc/platforms/cell directory. Arnd
next prev parent reply other threads:[~2020-11-27 20:32 UTC|newest] Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <email@example.com> 2020-11-20 23:14 ` [PATCH v2 01/24] exec: Move unshare_files to fix posix file locking during exec Eric W. Biederman 2020-11-20 23:58 ` Linus Torvalds 2020-12-07 22:22 ` Al Viro [not found] ` <firstname.lastname@example.org> 2020-12-07 23:35 ` Al Viro 2020-11-20 23:14 ` [PATCH v2 02/24] exec: Simplify unshare_files Eric W. Biederman 2020-11-23 17:50 ` Oleg Nesterov 2020-11-23 18:25 ` Linus Torvalds [not found] ` <email@example.com> [not found] ` <firstname.lastname@example.org> 2020-11-24 19:58 ` Linus Torvalds 2020-11-24 20:14 ` Arnd Bergmann 2020-11-24 23:44 ` Geoff Levand 2020-11-25 1:16 ` Eric W. Biederman 2020-11-27 20:29 ` Arnd Bergmann [this message] 2020-11-30 21:37 ` Eric W. Biederman 2020-12-01 9:46 ` Michael Ellerman 2020-11-25 21:51 ` [RFC][PATCH] coredump: Document coredump code exclusively used by cell spufs Eric W. Biederman 2020-12-02 15:20 ` Eric W. Biederman 2020-12-02 15:58 ` Arnd Bergmann 2020-12-07 22:32 ` [PATCH v2 02/24] exec: Simplify unshare_files Al Viro 2020-11-20 23:14 ` [PATCH v2 03/24] exec: Remove reset_files_struct Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 04/24] kcmp: In kcmp_epoll_target use fget_task Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 05/24] bpf: In bpf_task_fd_query " Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 06/24] proc/fd: In proc_fd_link " Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 07/24] file: Rename __fcheck_files to files_lookup_fd_raw Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 08/24] file: Factor files_lookup_fd_locked out of fcheck_files Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 09/24] file: Replace fcheck_files with files_lookup_fd_rcu Eric W. Biederman 2020-12-07 22:46 ` Al Viro 2020-12-07 22:49 ` Al Viro 2020-12-09 16:54 ` Al Viro 2020-12-09 17:44 ` Paul E. McKenney 2020-11-20 23:14 ` [PATCH v2 10/24] file: Rename fcheck lookup_fd_rcu Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 11/24] file: Implement task_lookup_fd_rcu Eric W. Biederman 2020-11-21 18:19 ` Cyrill Gorcunov [not found] ` <email@example.com> 2020-11-22 13:52 ` Cyrill Gorcunov 2020-11-20 23:14 ` [PATCH v2 12/24] proc/fd: In tid_fd_mode use task_lookup_fd_rcu Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 13/24] kcmp: In get_file_raw_ptr " Eric W. Biederman 2020-11-23 21:05 ` Cyrill Gorcunov 2020-11-20 23:14 ` [PATCH v2 14/24] file: Implement task_lookup_next_fd_rcu Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 15/24] proc/fd: In proc_readfd_common use task_lookup_next_fd_rcu Eric W. Biederman 2020-12-07 23:29 ` Al Viro [not found] ` <firstname.lastname@example.org> 2020-12-09 4:07 ` Al Viro [not found] ` <email@example.com> 2020-12-09 14:23 ` Al Viro 2020-12-09 18:04 ` [PATCH] files: rcu free files_struct Eric W. Biederman 2020-12-09 19:13 ` Linus Torvalds 2020-12-09 19:50 ` Al Viro 2020-12-09 21:32 ` Eric W. Biederman 2020-12-10 6:13 ` Al Viro 2020-12-10 19:29 ` Eric W. Biederman 2020-12-10 21:36 ` Al Viro 2020-12-10 22:30 ` Christian Brauner 2020-12-10 22:54 ` Al Viro 2020-12-10 23:10 ` Al Viro 2020-12-09 21:42 ` [PATCH -1/24] exec: Don't open code get_close_on_exec Eric W. Biederman 2020-12-09 22:04 ` [PATCH] files: rcu free files_struct Eric W. Biederman 2020-12-09 19:49 ` Matthew Wilcox 2020-12-09 22:06 ` Eric W. Biederman 2020-12-09 22:58 ` Al Viro 2020-12-09 23:01 ` Linus Torvalds 2020-12-09 23:04 ` Linus Torvalds 2020-12-09 23:07 ` Matthew Wilcox 2020-12-09 23:26 ` Paul E. McKenney 2020-12-09 23:29 ` Linus Torvalds 2020-12-10 0:39 ` Paul E. McKenney 2020-12-10 0:41 ` Linus Torvalds 2020-12-10 0:57 ` Paul E. McKenney 2020-11-20 23:14 ` [PATCH v2 16/24] bpf/task_iter: In task_file_seq_get_next use task_lookup_next_fd_rcu Eric W. Biederman 2020-11-23 17:06 ` Yonghong Song 2020-11-20 23:14 ` [PATCH v2 17/24] proc/fd: In fdinfo seq_show don't use get_files_struct Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 18/24] file: Merge __fd_install into fd_install Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 19/24] file: In f_dupfd read RLIMIT_NOFILE once Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 20/24] file: Merge __alloc_fd into alloc_fd Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 21/24] file: Rename __close_fd to close_fd and remove the files parameter Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 22/24] file: Replace ksys_close with close_fd Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 23/24] file: Rename __close_fd_get_file close_fd_get_file Eric W. Biederman 2020-11-20 23:14 ` [PATCH v2 24/24] file: Remove get_files_struct Eric W. Biederman 2020-11-21 0:05 ` [PATCH v2 00/24] exec: Move unshare_files and guarantee files_struct.count is correct Linus Torvalds 2020-11-28 5:12 ` Al Viro 2020-12-07 23:56 ` Al Viro
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