From b0519089ed0efd8b8d92d24e9d972cfdb513232a Mon Sep 17 00:00:00 2001 From: emaste Date: Mon, 25 Nov 2013 15:58:48 +0000 Subject: 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) --- sys/i386/linux/linux_sysvec.c | 24 ++---------------------- 1 file changed, 2 insertions(+), 22 deletions(-) (limited to 'sys/i386/linux/linux_sysvec.c') diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c index 71417e0..0ad6791 100644 --- a/sys/i386/linux/linux_sysvec.c +++ b/sys/i386/linux/linux_sysvec.c @@ -684,17 +684,7 @@ linux_sigreturn(struct thread *td, struct linux_sigreturn_args *args) */ #define EFLAGS_SECURE(ef, oef) ((((ef) ^ (oef)) & ~PSL_USERCHANGE) == 0) eflags = frame.sf_sc.sc_eflags; - /* - * XXX do allow users 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. - */ - if (!EFLAGS_SECURE(eflags & ~PSL_RF, regs->tf_eflags & ~PSL_RF)) + if (!EFLAGS_SECURE(eflags, regs->tf_eflags)) return(EINVAL); /* @@ -785,17 +775,7 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_sigreturn_args *args) */ #define EFLAGS_SECURE(ef, oef) ((((ef) ^ (oef)) & ~PSL_USERCHANGE) == 0) eflags = context->sc_eflags; - /* - * XXX do allow users 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. - */ - if (!EFLAGS_SECURE(eflags & ~PSL_RF, regs->tf_eflags & ~PSL_RF)) + if (!EFLAGS_SECURE(eflags, regs->tf_eflags)) return(EINVAL); /* -- cgit v1.1