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Use get_mcontext() to construct the signal context in sendsig() and

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use set_mcontext() to restore the context in sigreturn(). Since we
put the syscall number and the syscall arguments in the trapframe
(we don't save the scratch registers for syscalls, which allows us
to reuse the space to our advantage), create a MD specific flag so
that we save the scratch registers even for syscalls. We would not
be able to restart a syscall otherwise.

The signal trampoline does not need to flush the regiters anymore,
because get_mcontext() already handles that. In fact, if we set up
the context correctly, we do not need to have a trampoline at all.
This change however only minimally changes the trampoline code. In
follow-up commits this can be further optimized.

Note that normally we preserve cfm and iip in the trapframe created
by the EPC syscall path when we restore a context in set_mcontext()
because those fields are not normally set for a synchronuous context.
The kernel puts the return address and frame info of the syscall
stub in there. By preserving these fields we hide this detail from
userland which allows us to use setcontext(2) for user created
contexts. However, sigreturn() is commonly called from the trampoline,
which means that if we preserve cfm and iip in all cases, we would
return to the trampoline after the sigreturn(), which means we hit
the safety net: we call exit(2). So, we do not preserve cfm and iip
when we have a synchronous context that also has scratch registers
(the uncommon context created by sendsig() only), under the assumption
that if such a context is created in userland, something special is
going on and the use of cfm and iip is then just another quirk. All
this is invisible in the common case.
This commit is contained in:
Marcel Moolenaar 2003-11-09 22:17:36 +00:00
parent 637315ed9c
commit ac8c7680a6
3 changed files with 58 additions and 117 deletions
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106
sys/ia64/ia64/machdep.c
View file

@ -859,7 +859,6 @@ sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
struct trapframe *tf;
struct sigacts *psp;
struct sigframe sf, *sfp;
mcontext_t *mc;
u_int64_t sbs, sp;
int oonstack;
@ -910,25 +909,7 @@ sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
mtx_unlock(&psp->ps_mtx);
PROC_UNLOCK(p);
mc = &sf.sf_uc.uc_mcontext;
mc->mc_special = tf->tf_special;
mc->mc_scratch = tf->tf_scratch;
if ((tf->tf_flags & FRAME_SYSCALL) == 0) {
mc->mc_flags |= _MC_FLAGS_ASYNC_CONTEXT;
mc->mc_scratch_fp = tf->tf_scratch_fp;
/*
* XXX High FP. If the process has never used the high FP,
* mark the high FP as valid (zero defaults). If the process
* did use the high FP, then store them in the PCB if not
* already there (ie get them from the CPU that has them)
* and write them in the context.
*/
} else
mc->mc_flags |= _MC_FLAGS_SCRATCH_VALID;
save_callee_saved(&mc->mc_preserved);
save_callee_saved_fp(&mc->mc_preserved_fp);
get_mcontext(td, &sf.sf_uc.uc_mcontext, GET_MC_IA64_SCRATCH);
/* Copy the frame out to userland. */
if (copyout(&sf, sfp, sizeof(sf)) != 0) {
@ -1006,7 +987,6 @@ sigreturn(struct thread *td,
{
ucontext_t uc;
struct trapframe *tf;
struct __mcontext *mc;
struct proc *p;
struct pcb *pcb;
@ -1021,32 +1001,7 @@ sigreturn(struct thread *td,
if (copyin(uap->sigcntxp, (caddr_t)&uc, sizeof(uc)))
return (EFAULT);
/*
* Restore the user-supplied information.
* XXX Very much incomplete.
*/
mc = &uc.uc_mcontext;
tf->tf_special = mc->mc_special;
if (mc->mc_flags & _MC_FLAGS_ASYNC_CONTEXT) {
tf->tf_scratch = mc->mc_scratch;
tf->tf_scratch_fp = mc->mc_scratch_fp;
/* XXX high FP. */
} else {
if ((mc->mc_flags & _MC_FLAGS_SCRATCH_VALID) == 0) {
tf->tf_scratch.gr15 = 0;
if (mc->mc_flags & _MC_FLAGS_RETURN_VALID) {
tf->tf_scratch.gr8 = mc->mc_scratch.gr8;
tf->tf_scratch.gr9 = mc->mc_scratch.gr9;
tf->tf_scratch.gr10 = mc->mc_scratch.gr10;
tf->tf_scratch.gr11 = mc->mc_scratch.gr11;
}
} else
tf->tf_scratch = mc->mc_scratch;
}
restore_callee_saved(&mc->mc_preserved);
restore_callee_saved_fp(&mc->mc_preserved_fp);
set_mcontext(td, &uc.uc_mcontext);
PROC_LOCK(p);
#if defined(COMPAT_43) || defined(COMPAT_SUNOS)
@ -1075,44 +1030,50 @@ freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
int
get_mcontext(struct thread *td, mcontext_t *mc, int flags)
{
struct _special s;
struct trapframe *tf;
uint64_t bspst, kstk, rnat;
tf = td->td_frame;
bzero(mc, sizeof(*mc));
s = tf->tf_special;
if (s.ndirty != 0) {
kstk = td->td_kstack + (s.bspstore & 0x1ffUL);
if (tf->tf_special.ndirty != 0) {
kstk = td->td_kstack + (tf->tf_special.bspstore & 0x1ffUL);
__asm __volatile("mov ar.rsc=0;;");
__asm __volatile("mov %0=ar.bspstore" : "=r"(bspst));
/* Make sure we have all the user registers written out. */
if (bspst - kstk < s.ndirty) {
if (bspst - kstk < tf->tf_special.ndirty) {
__asm __volatile("flushrs;;");
__asm __volatile("mov %0=ar.bspstore" : "=r"(bspst));
}
__asm __volatile("mov %0=ar.rnat;;" : "=r"(rnat));
__asm __volatile("mov ar.rsc=3");
copyout((void*)kstk, (void*)s.bspstore, s.ndirty);
kstk += s.ndirty;
s.bspstore += s.ndirty;
s.ndirty = 0;
s.rnat = (bspst > kstk && (bspst & 0x1ffUL) < (kstk & 0x1ffUL))
copyout((void*)kstk, (void*)tf->tf_special.bspstore,
tf->tf_special.ndirty);
kstk += tf->tf_special.ndirty;
tf->tf_special.bspstore += tf->tf_special.ndirty;
tf->tf_special.ndirty = 0;
tf->tf_special.rnat =
(bspst > kstk && (bspst & 0x1ffUL) < (kstk & 0x1ffUL))
? *(uint64_t*)(kstk | 0x1f8UL) : rnat;
}
if (tf->tf_flags & FRAME_SYSCALL) {
/*
* Put the syscall return values in the context. We need this
* for swapcontext() to work. Note that we don't use gr11 in
* the kernel, but the runtime specification defines it as a
* return register, just like gr8-gr10.
*/
mc->mc_flags |= _MC_FLAGS_RETURN_VALID;
if ((flags & GET_MC_CLEAR_RET) == 0) {
mc->mc_scratch.gr8 = tf->tf_scratch.gr8;
mc->mc_scratch.gr9 = tf->tf_scratch.gr9;
mc->mc_scratch.gr10 = tf->tf_scratch.gr10;
mc->mc_scratch.gr11 = tf->tf_scratch.gr11;
if (flags & GET_MC_IA64_SCRATCH) {
mc->mc_flags |= _MC_FLAGS_SCRATCH_VALID;
mc->mc_scratch = tf->tf_scratch;
} else {
/*
* Put the syscall return values in the context. We
* need this for swapcontext() to work. Note that we
* don't use gr11 in the kernel, but the runtime
* specification defines it as a return register,
* just like gr8-gr10.
*/
mc->mc_flags |= _MC_FLAGS_RETURN_VALID;
if ((flags & GET_MC_CLEAR_RET) == 0) {
mc->mc_scratch.gr8 = tf->tf_scratch.gr8;
mc->mc_scratch.gr9 = tf->tf_scratch.gr9;
mc->mc_scratch.gr10 = tf->tf_scratch.gr10;
mc->mc_scratch.gr11 = tf->tf_scratch.gr11;
}
}
} else {
mc->mc_flags |= _MC_FLAGS_ASYNC_CONTEXT;
@ -1120,7 +1081,7 @@ get_mcontext(struct thread *td, mcontext_t *mc, int flags)
mc->mc_scratch_fp = tf->tf_scratch_fp;
/* XXX High FP */
}
mc->mc_special = s;
mc->mc_special = tf->tf_special;
save_callee_saved(&mc->mc_preserved);
save_callee_saved_fp(&mc->mc_preserved_fp);
return (0);
@ -1155,9 +1116,10 @@ set_mcontext(struct thread *td, const mcontext_t *mc)
/* XXX High FP */
} else {
KASSERT((tf->tf_flags & FRAME_SYSCALL) != 0, ("foo"));
s.cfm = tf->tf_special.cfm;
s.iip = tf->tf_special.iip;
if ((mc->mc_flags & _MC_FLAGS_SCRATCH_VALID) == 0) {
s.cfm = tf->tf_special.cfm;
s.iip = tf->tf_special.iip;
tf->tf_scratch.gr15 = 0; /* Clear syscall nr. */
if (mc->mc_flags & _MC_FLAGS_RETURN_VALID) {
tf->tf_scratch.gr8 = mc->mc_scratch.gr8;
tf->tf_scratch.gr9 = mc->mc_scratch.gr9;

62
sys/ia64/ia64/syscall.S
View file

@ -181,58 +181,32 @@ ENTRY(break_sigtramp, 0)
END(break_sigtramp)
ENTRY(epc_sigtramp, 0)
{ .mib
mov ar.rsc=0
cmp.ne p15,p0=0,gp
cover
;;
}
{ .mmi
flushrs
(p15) invala
add r16=16+UC_MCONTEXT+MC_SPECIAL,sp
;;
}
{ .mmi
mov r17=ar.bsp
mov r18=ar.rnat
add r14=14*8,r16
;;
}
{ .mmi
(p15) mov ar.bspstore=gp
ld8 r19=[r14],-9*8 // cfm
add r15=6*8,r16
;;
}
{ .mmi
st8 [r14]=r17,8*8 // bspstore
st8 [r15]=r18,8*8 // rnat
dep r19=r19,r19,7,7
;;
}
{ .mmi
st8 [r14]=r0 // ndirty
st8 [r15]=r19 // cfm
nop 0
;;
}
{ .mmi
alloc r14=ar.pfs, 0, 0, 3, 0
mov ar.rsc=15
mov out0=r8
;;
}
{ .mmi
ld8 r16=[r10],8 // function address
mov ar.rsc=0
cmp.ne p15,p0=0,gp
;;
ld8 gp=[r10] // function's gp value
}
{ .mmi
(p15) invala
(p15) mov ar.bspstore=gp
mov b7=r16
;;
}
{ .mib
{ .mmb
alloc r14=ar.pfs, 0, 0, 3, 0
mov ar.rsc=15
nop 0
;;
}
{ .mii
ld8 gp=[r10] // function's gp value
mov out0=r8
mov out1=r9
}
{ .mfb
add out2=16,sp
nop 0
br.call.sptk rp=b7
;;
}

7
sys/ia64/include/ucontext.h
View file

@ -1,5 +1,5 @@
/*-
* Copyright (c) 1999 Marcel Moolenaar
* Copyright (c) 1999, 2003 Marcel Moolenaar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -96,4 +96,9 @@ typedef struct __mcontext {
struct _high_fp mc_high_fp;
} mcontext_t;
#ifdef _KERNEL
/* Flags for get_mcontext(). See also <sys/ucontext.h>. */
#define GET_MC_IA64_SCRATCH 0x10
#endif
#endif /* !_MACHINE_UCONTEXT_H_ */