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| author | emaste <emaste@FreeBSD.org> | 2013-11-14 15:37:20 +0000 |
|---|---|---|
| committer | emaste <emaste@FreeBSD.org> | 2013-11-14 15:37:20 +0000 |
| commit | 9dcbb8e88d3f051a7ee6593c53e5ad49e4904bfd (patch) | |
| tree | e176fc3a1f9254f29a0794cb5f498dea6487cc1e /sys/x86/include/psl.h | |
| parent | 544cc7da1e2d2b5eaee7344d5fdaebfba13d6ec5 (diff) | |
| download | FreeBSD-src-9dcbb8e88d3f051a7ee6593c53e5ad49e4904bfd.zip FreeBSD-src-9dcbb8e88d3f051a7ee6593c53e5ad49e4904bfd.tar.gz | |
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
Diffstat (limited to 'sys/x86/include/psl.h')
| -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_ */ |
