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| author | emaste <emaste@FreeBSD.org> | 2013-11-25 15:58:48 +0000 |
|---|---|---|
| committer | emaste <emaste@FreeBSD.org> | 2013-11-25 15:58:48 +0000 |
| commit | b0519089ed0efd8b8d92d24e9d972cfdb513232a (patch) | |
| tree | 1700a610df043601614f2bd2a345a3bca0ec7cd6 /sys/x86 | |
| parent | 79f55b704935cf6e1a4f60d33d1ce87bcf710f08 (diff) | |
| download | FreeBSD-src-b0519089ed0efd8b8d92d24e9d972cfdb513232a.zip FreeBSD-src-b0519089ed0efd8b8d92d24e9d972cfdb513232a.tar.gz | |
MFC r258135: x86: Allow users to change PSL_RF via ptrace(PT_SETREGS...)
Debuggers may need to change PSL_RF. Note that tf_eflags is already stored
in the signal context during signal handling and PSL_RF previously could
be modified via sigreturn, so this change should not provide any new
ability to userspace.
For background see the thread at:
http://lists.freebsd.org/pipermail/freebsd-i386/2007-September/005910.html
Reviewed by: jhb, kib
Sponsored by: DARPA, AFRL
Approved by: re (gjb)
Diffstat (limited to 'sys/x86')
| -rw-r--r-- | sys/x86/include/psl.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/sys/x86/include/psl.h b/sys/x86/include/psl.h index 12d05c5..47851e0 100644 --- a/sys/x86/include/psl.h +++ b/sys/x86/include/psl.h @@ -77,8 +77,16 @@ * is undesirable but it may as well be allowed since users can inflict * it on the kernel directly. Changes to PSL_AC are silently ignored on * 386's. + * + * Users are allowed to change the privileged flag PSL_RF. The cpu sets PSL_RF + * in tf_eflags for faults. Debuggers should sometimes set it there too. + * tf_eflags is kept in the signal context during signal handling and there is + * no other place to remember it, so the PSL_RF bit may be corrupted by the + * signal handler without us knowing. Corruption of the PSL_RF bit at worst + * causes one more or one less debugger trap, so allowing it is fairly + * harmless. */ #define PSL_USERCHANGE (PSL_C | PSL_PF | PSL_AF | PSL_Z | PSL_N | PSL_T \ - | PSL_D | PSL_V | PSL_NT | PSL_AC | PSL_ID) + | PSL_D | PSL_V | PSL_NT | PSL_RF | PSL_AC | PSL_ID) #endif /* !_MACHINE_PSL_H_ */ |
