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35 #ifndef _MACHINE_PSL_H_
36 #define _MACHINE_PSL_H_
39 * 386 processor status longword.
41 #define PSL_C 0x00000001 /* carry bit */
42 #define PSL_PF 0x00000004 /* parity bit */
43 #define PSL_AF 0x00000010 /* bcd carry bit */
44 #define PSL_Z 0x00000040 /* zero bit */
45 #define PSL_N 0x00000080 /* negative bit */
46 #define PSL_T 0x00000100 /* trace enable bit */
47 #define PSL_I 0x00000200 /* interrupt enable bit */
48 #define PSL_D 0x00000400 /* string instruction direction bit */
49 #define PSL_V 0x00000800 /* overflow bit */
50 #define PSL_IOPL 0x00003000 /* i/o privilege level */
51 #define PSL_NT 0x00004000 /* nested task bit */
52 #define PSL_RF 0x00010000 /* resume flag bit */
53 #define PSL_VM 0x00020000 /* virtual 8086 mode bit */
54 #define PSL_AC 0x00040000 /* alignment checking */
55 #define PSL_VIF 0x00080000 /* virtual interrupt enable */
56 #define PSL_VIP 0x00100000 /* virtual interrupt pending */
57 #define PSL_ID 0x00200000 /* identification bit */
60 * The i486 manual says that we are not supposed to change reserved flags,
61 * but this is too much trouble since the reserved flags depend on the cpu
62 * and setting them to their historical values works in practice.
64 #define PSL_RESERVED_DEFAULT 0x00000002
67 * Initial flags for kernel and user mode. The kernel later inherits
68 * PSL_I and some other flags from user mode.
70 #define PSL_KERNEL PSL_RESERVED_DEFAULT
71 #define PSL_USER (PSL_RESERVED_DEFAULT | PSL_I)
74 * Bits that can be changed in user mode on 486's. We allow these bits
75 * to be changed using ptrace(), sigreturn() and procfs. Setting PS_NT
76 * is undesirable but it may as well be allowed since users can inflict
77 * it on the kernel directly. Changes to PSL_AC are silently ignored on
80 * Users are allowed to change the privileged flag PSL_RF. The cpu sets PSL_RF
81 * in tf_eflags for faults. Debuggers should sometimes set it there too.
82 * tf_eflags is kept in the signal context during signal handling and there is
83 * no other place to remember it, so the PSL_RF bit may be corrupted by the
84 * signal handler without us knowing. Corruption of the PSL_RF bit at worst
85 * causes one more or one less debugger trap, so allowing it is fairly
88 #define PSL_USERCHANGE (PSL_C | PSL_PF | PSL_AF | PSL_Z | PSL_N | PSL_T \
89 | PSL_D | PSL_V | PSL_NT | PSL_RF | PSL_AC | PSL_ID)
91 #endif /* !_MACHINE_PSL_H_ */