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Groups > linux.kernel > #1218453
| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') |
| Date | 2015-09-03 19:30 +0200 |
| Message-ID | <q4GuJ-1LD-1@gated-at.bofh.it> (permalink) |
| References | (10 earlier) <q4BEK-3hX-23@gated-at.bofh.it> <q4BEL-3hX-33@gated-at.bofh.it> <q4EVX-7Sc-1@gated-at.bofh.it> <q4G1I-Xg-19@gated-at.bofh.it> <q4GuJ-1LD-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Sep 3, 2015 at 10:19 AM, Stas Sergeev <stsp@list.ru> wrote: > 03.09.2015 19:57, Linus Torvalds пишет: >> On Thu, Sep 3, 2015 at 8:44 AM, Austin S Hemmelgarn >> <ahferroin7@gmail.com> wrote: >>> >>> This lets you turn this on or off at runtime. >> >> Tangential aside: we already effectively have a flag that could turn >> off vm86 mode dynamically: /proc/sys/vm/mmap_min_addr. >> >> Sadly (or not) we default it to 4096, which still leaves vm86 mode >> usable, although it effectively disables *dos* use for it. Which is >> kind of the worst of both worlds: you can use the vm86() system call >> for bad things (if you can find a hole in it), but you probably cannot >> actually use it for DOS emulation, because the traditional BIOS data >> segment is at 0040. >> >> Anyway, what that means is that pretty much the only *valid* use of >> vm86() mode is probably when the system maintainer has set >> 'mmap_min_addr' to zero. So we could probably use that as an already >> existing flag that disallows vm86 by our current default values. >> >> Stas - can you confirm that to actually use vm86 mode, you end up >> setting that mmap_min_addr thing to zero? Or do you end up using a >> mixed-mode setup, where you use vm86() for most things, but emulate >> things that trap in the zero page? > Yes, good point. > dosemu complains about /proc/sys/vm/mmap_min_addr. > Trapping on zero-page access will likely not work, because > IIRC some distros raise that value even more. > So yes, please use that to completely disable vm86(). > You won't even break dosemu's checks, because it (obviously) > tries mmap() before trying vm86(). > I'm okay with that. Shall I send a patch? There's also vbetool, but I think that almost everyone considers it dead at this point, and it seems reasonably likely that it needs mmap_min_addr == 0 as well. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 11:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 16:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Kees Cook <keescook@chromium.org> - 2015-09-02 17:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 19:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 19:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 20:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 22:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 23:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 23:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 23:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 23:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-02 23:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 14:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 14:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 17:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 18:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 21:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 23:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Chuck Ebbert <cebbert.lkml@gmail.com> - 2015-09-04 12:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 12:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-04 14:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 15:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-04 22:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 23:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 23:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Raymond Jennings <shentino@gmail.com> - 2015-09-05 00:50 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-05 01:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-04 00:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Linus Torvalds <torvalds@linux-foundation.org> - 2015-09-03 19:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-03 19:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:40 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 19:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Stas Sergeev <stsp@list.ru> - 2015-09-03 14:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-09-03 14:10 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Kees Cook <keescook@chromium.org> - 2015-09-02 20:00 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Andy Lutomirski <luto@amacapital.net> - 2015-09-02 20:20 +0200
Re: stop breaking dosemu (Re: x86/kconfig/32: Rename CONFIG_VM86 and default it to 'n') Josh Boyer <jwboyer@fedoraproject.org> - 2015-09-02 22:30 +0200
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