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sound: Improve hw.snd.compat_linux_mmap #29

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christos wants to merge 2 commits from christos/protexec into main AGit
pull from: christos/protexec
merge into: FreeBSD:main
Conversation 6 Commits 2 Files changed 2 +24 -19
christos commented 2026-05-15 14:09:51 +00:00
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  • Reject PROT_EXEC in all cases when Linux support is not compiled in.
  • Define sysctl only when Linux support is compiled in.
  • Document better.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

- Reject PROT_EXEC in all cases when Linux support is not compiled in. - Define sysctl only when Linux support is compiled in. - Document better. Sponsored by: The FreeBSD Foundation MFC after: 1 week
sound: Improve hw.snd.compat_linux_mmap
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eb02ece9c3 
- Reject PROT_EXEC in all cases when Linux support is not compiled in.
- Define sysctl only when Linux support is compiled in.
- Document better.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
emaste reviewed 2026-05-15 14:27:13 +00:00
share/man/man4/pcm.4
@ -257,1 +257,3 @@
Linux
This
.Xr sysctl 8
variable is available only when Linux support is compiled into the kernel, and
emaste commented 2026-05-15 14:27:13 +00:00
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probably "Linux application support" or similar (do we have a consistent way to refer to the Linuxulator)?

probably "Linux application support" or similar (do we have a consistent way to refer to the Linuxulator)?
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emaste reviewed 2026-05-15 14:28:31 +00:00
share/man/man4/pcm.4
@ -258,0 +258,4 @@
.Xr sysctl 8
variable is available only when Linux support is compiled into the kernel, and
affects Linux binaries only.
It is a hack to get around the fact that Linux sets PROT_EXEC automatically
emaste commented 2026-05-15 14:28:31 +00:00
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Per the IRC discussion, Linux doesn't do this universally, it's really a Linuxulator quirk that we'll hopefully fix. And it's presumably only i386 Linux emulation?

Per the IRC discussion, Linux doesn't do this universally, it's really a Linuxulator quirk that we'll hopefully fix. And it's presumably only i386 Linux emulation?
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emaste reviewed 2026-05-15 14:30:29 +00:00
share/man/man4/pcm.4
@ -258,2 +263,3 @@
.Xr mmap 2
compatibility.
call, which
.Fx
emaste commented 2026-05-15 14:30:29 +00:00
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The issue is that older i386 processors did not have a way to allow R or W without X, so you could set PROT_READ | PROT_WRITE and then execute that memory (on both Linux and FreeBSD). Some software took advantage of that (maybe just out of laziness).

The issue is that older i386 processors did not have a way to allow R or W without X, so you could set `PROT_READ | PROT_WRITE` and then execute that memory (on both Linux and FreeBSD). Some software took advantage of that (maybe just out of laziness).
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2026-05-15 14:34:43 +00:00 Compare
emaste commented 2026-05-15 14:39:15 +00:00
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Some more comments via IRC. It looks like the Linuxulator was fixed in 97d06da692 and we can probably just do away with the hack altogether. IMO we should go with this change (with a few man page tweaks), then flip the default in main.

Some more comments via IRC. It looks like the Linuxulator was fixed in 97d06da6923d91fea748c5e153bb1abbd220cefa and we can probably just do away with the hack altogether. IMO we should go with this change (with a few man page tweaks), then flip the default in main.
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2026-05-15 14:41:50 +00:00 Compare
sound: Force-disable hw.snd.compat_linux_mmap by default
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d01e8e2302 
Eventually this hack will be removed, so start by disabling it by
default.

Sponsored by:	The FreeBSD Foundation
MFC after:	12 months
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2026-05-15 14:52:33 +00:00 Compare
emaste approved these changes 2026-05-15 14:56:19 +00:00
christos commented 2026-05-15 15:12:54 +00:00
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Committed.

Committed.
christos closed this pull request 2026-05-15 15:12:55 +00:00
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Pull request closed

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