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sparc: Fix debugger syscall restart interactions.

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So, forever, we've had this ptrace_signal_deliver implementation
which tries to handle all of the nasties that can occur when the
debugger looks at a process about to take a signal.  It's meant
to address all of these issues inside of the kernel so that the
debugger need not be mindful of such things.

Problem is, this doesn't work.

The idea was that we should do the syscall restart business first, so
that the debugger captures that state.  Otherwise, if the debugger for
example saves the child's state, makes the child execute something
else, then restores the saved state, we won't handle the syscall
restart properly because we lose the "we're in a syscall" state.

The code here worked for most cases, but if the debugger actually
passes the signal through to the child unaltered, it's possible that
we would do a syscall restart when we shouldn't have.

In particular this breaks the case of debugging a process under a gdb
which is being debugged by yet another gdb.  gdb uses sigsuspend
to wait for SIGCHLD of the inferior, but if gdb itself is being
debugged by a top-level gdb we get a ptrace_stop().  The top-level gdb
does a PTRACE_CONT with SIGCHLD to let the inferior gdb see the
signal.  But ptrace_signal_deliver() assumed the debugger would cancel
out the signal and therefore did a syscall restart, because the return
error was ERESTARTNOHAND.

Fix this by simply making ptrace_signal_deliver() a nop, and providing
a way for the debugger to control system call restarting properly:

1) Report a "in syscall" software bit in regs->{tstate,psr}.
   It is set early on in trap entry to a system call and is fully
   visible to the debugger via ptrace() and regsets.

2) Test this bit right before doing a syscall restart.  We have
   to do a final recheck right after get_signal_to_deliver() in
   case the debugger cleared the bit during ptrace_stop().

3) Clear the bit in trap return so we don't accidently try to set
   that bit in the real register.

As a result we also get a ptrace_{is,clear}_syscall() for sparc32 just
like sparc64 has.

M68K has this same exact bug, and is now the only other user of the
ptrace_signal_deliver hook.  It needs to be fixed in the same exact
way as sparc.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2008-05-11 02:07:19 -07:00
parent 986bef854f
commit 28e6103665
17 changed files with 116 additions and 120 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
arch/sparc/kernel/entry.S
View file

@ -1306,6 +1306,8 @@ ret_from_fork:
.align 4
.globl linux_sparc_syscall
linux_sparc_syscall:
sethi %hi(PSR_SYSCALL), %l4
or %l0, %l4, %l0
/* Direct access to user regs, must faster. */
cmp %g1, NR_SYSCALLS
bgeu linux_sparc_ni_syscall

4
arch/sparc/kernel/ptrace.c
View file

@ -170,8 +170,8 @@ static int genregs32_set(struct task_struct *target,
switch (pos) {
case 32: /* PSR */
psr = regs->psr;
psr &= ~PSR_ICC;
psr |= (reg & PSR_ICC);
psr &= ~(PSR_ICC | PSR_SYSCALL);
psr |= (reg & (PSR_ICC | PSR_SYSCALL));
regs->psr = psr;
break;
case 33: /* PC */

11
arch/sparc/kernel/rtrap.S
View file

@ -50,8 +50,9 @@ rtrap_7win_patch5: and %g1, 0x7f, %g1
ret_trap_entry:
ret_trap_lockless_ipi:
andcc %t_psr, PSR_PS, %g0
sethi %hi(PSR_SYSCALL), %g1
be 1f
nop
andn %t_psr, %g1, %t_psr
wr %t_psr, 0x0, %psr
b ret_trap_kernel
@ -73,7 +74,6 @@ signal_p:
ld [%sp + STACKFRAME_SZ + PT_PSR], %t_psr
mov %l5, %o1
mov %l6, %o2
call do_signal
add %sp, STACKFRAME_SZ, %o0 ! pt_regs ptr
@ -81,6 +81,8 @@ signal_p:
ld [%sp + STACKFRAME_SZ + PT_PSR], %t_psr
clr %l6
ret_trap_continue:
sethi %hi(PSR_SYSCALL), %g1
andn %t_psr, %g1, %t_psr
wr %t_psr, 0x0, %psr
WRITE_PAUSE
@ -137,8 +139,9 @@ ret_trap_userwins_ok:
LOAD_PT_PRIV(sp, t_psr, t_pc, t_npc)
or %t_pc, %t_npc, %g2
andcc %g2, 0x3, %g0
sethi %hi(PSR_SYCALL), %g2
be 1f
nop
andn %t_psr, %g2, %t_psr
b ret_trap_unaligned_pc
add %sp, STACKFRAME_SZ, %o0
@ -201,6 +204,8 @@ rtrap_patch5: and %g1, 0xff, %g1
1:
LOAD_PT_ALL(sp, t_psr, t_pc, t_npc, g1)
2:
sethi %hi(PSR_SYSCALL), %twin_tmp1
andn %t_psr, %twin_tmp1, %t_psr
wr %t_psr, 0x0, %psr
WRITE_PAUSE

64
arch/sparc/kernel/signal.c
View file

@ -145,6 +145,9 @@ asmlinkage void do_sigreturn(struct pt_regs *regs)
regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
| (regs->psr & (PSR_ICC | PSR_EF));
/* Prevent syscall restart. */
pt_regs_clear_syscall(regs);
err |= __get_user(fpu_save, &sf->fpu_save);
if (fpu_save)
@ -199,6 +202,9 @@ asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);
/* Prevent syscall restart. */
pt_regs_clear_syscall(regs);
err |= __get_user(fpu_save, &sf->fpu_save);
if (fpu_save)
@ -507,26 +513,36 @@ static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0, int restart_syscall)
asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0)
{
siginfo_t info;
struct sparc_deliver_cookie cookie;
struct k_sigaction ka;
int signr;
int restart_syscall;
sigset_t *oldset;
siginfo_t info;
int signr;
cookie.restart_syscall = restart_syscall;
cookie.orig_i0 = orig_i0;
if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
restart_syscall = 1;
else
restart_syscall = 0;
if (test_thread_flag(TIF_RESTORE_SIGMASK))
oldset = &current->saved_sigmask;
else
oldset = &current->blocked;
signr = get_signal_to_deliver(&info, &ka, regs, &cookie);
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
/* If the debugger messes with the program counter, it clears
* the software "in syscall" bit, directing us to not perform
* a syscall restart.
*/
if (restart_syscall && !pt_regs_is_syscall(regs))
restart_syscall = 0;
if (signr > 0) {
if (cookie.restart_syscall)
syscall_restart(cookie.orig_i0, regs, &ka.sa);
if (restart_syscall)
syscall_restart(orig_i0, regs, &ka.sa);
handle_signal(signr, &ka, &info, oldset, regs);
/* a signal was successfully delivered; the saved
@ -538,16 +554,16 @@ asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0, int rest
clear_thread_flag(TIF_RESTORE_SIGMASK);
return;
}
if (cookie.restart_syscall &&
if (restart_syscall &&
(regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
regs->u_regs[UREG_I0] == ERESTARTSYS ||
regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
/* replay the system call when we are done */
regs->u_regs[UREG_I0] = cookie.orig_i0;
regs->u_regs[UREG_I0] = orig_i0;
regs->pc -= 4;
regs->npc -= 4;
}
if (cookie.restart_syscall &&
if (restart_syscall &&
regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
regs->u_regs[UREG_G1] = __NR_restart_syscall;
regs->pc -= 4;
@ -599,27 +615,3 @@ do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr,
out:
return ret;
}
void ptrace_signal_deliver(struct pt_regs *regs, void *cookie)
{
struct sparc_deliver_cookie *cp = cookie;
if (cp->restart_syscall &&
(regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
regs->u_regs[UREG_I0] == ERESTARTSYS ||
regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
/* replay the system call when we are done */
regs->u_regs[UREG_I0] = cp->orig_i0;
regs->pc -= 4;
regs->npc -= 4;
cp->restart_syscall = 0;
}
if (cp->restart_syscall &&
regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
regs->u_regs[UREG_G1] = __NR_restart_syscall;
regs->pc -= 4;
regs->npc -= 4;
cp->restart_syscall = 0;
}
}

7
arch/sparc64/kernel/etrap.S
View file

@ -27,11 +27,12 @@
.text
.align 64
.globl etrap, etrap_irq, etraptl1
.globl etrap_syscall, etrap, etrap_irq, etraptl1
etrap: rdpr %pil, %g2
etrap_irq:
TRAP_LOAD_THREAD_REG(%g6, %g1)
etrap_irq: clr %g3
etrap_syscall: TRAP_LOAD_THREAD_REG(%g6, %g1)
rdpr %tstate, %g1
or %g1, %g3, %g1
sllx %g2, 20, %g3
andcc %g1, TSTATE_PRIV, %g0
or %g1, %g3, %g1

12
arch/sparc64/kernel/ptrace.c
View file

@ -287,11 +287,11 @@ static int genregs64_set(struct task_struct *target,
32 * sizeof(u64),
33 * sizeof(u64));
if (!ret) {
/* Only the condition codes can be modified
* in the %tstate register.
/* Only the condition codes and the "in syscall"
* state can be modified in the %tstate register.
*/
tstate &= (TSTATE_ICC | TSTATE_XCC);
regs->tstate &= ~(TSTATE_ICC | TSTATE_XCC);
tstate &= (TSTATE_ICC | TSTATE_XCC | TSTATE_SYSCALL);
regs->tstate &= ~(TSTATE_ICC | TSTATE_XCC | TSTATE_SYSCALL);
regs->tstate |= tstate;
}
}
@ -657,8 +657,10 @@ static int genregs32_set(struct task_struct *target,
switch (pos) {
case 32: /* PSR */
tstate = regs->tstate;
tstate &= ~(TSTATE_ICC | TSTATE_XCC);
tstate &= ~(TSTATE_ICC | TSTATE_XCC | TSTATE_SYSCALL);
tstate |= psr_to_tstate_icc(reg);
if (reg & PSR_SYSCALL)
tstate |= TSTATE_SYSCALL;
regs->tstate = tstate;
break;
case 33: /* PC */

1
arch/sparc64/kernel/rtrap.S
View file

@ -257,6 +257,7 @@ rt_continue: ldx [%sp + PTREGS_OFF + PT_V9_G1], %g1
wr %o3, %g0, %y
wrpr %l4, 0x0, %pil
wrpr %g0, 0x1, %tl
andn %l1, TSTATE_SYSCALL, %l1
wrpr %l1, %g0, %tstate
wrpr %l2, %g0, %tpc
wrpr %o2, %g0, %tnpc

60
arch/sparc64/kernel/signal.c
View file

@ -333,7 +333,7 @@ void do_rt_sigreturn(struct pt_regs *regs)
regs->tnpc = tnpc;
/* Prevent syscall restart. */
pt_regs_clear_trap_type(regs);
pt_regs_clear_syscall(regs);
sigdelsetmask(&set, ~_BLOCKABLE);
spin_lock_irq(&current->sighand->siglock);
@ -499,7 +499,7 @@ static inline void handle_signal(unsigned long signr, struct k_sigaction *ka,
}
static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
struct sigaction *sa)
struct sigaction *sa)
{
switch (regs->u_regs[UREG_I0]) {
case ERESTART_RESTARTBLOCK:
@ -525,19 +525,17 @@ static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
*/
static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
{
struct signal_deliver_cookie cookie;
struct k_sigaction ka;
int restart_syscall;
sigset_t *oldset;
siginfo_t info;
int signr;
if (pt_regs_is_syscall(regs) &&
(regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) {
pt_regs_clear_trap_type(regs);
cookie.restart_syscall = 1;
restart_syscall = 1;
} else
cookie.restart_syscall = 0;
cookie.orig_i0 = orig_i0;
restart_syscall = 0;
if (test_thread_flag(TIF_RESTORE_SIGMASK))
oldset = &current->saved_sigmask;
@ -547,16 +545,25 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
#ifdef CONFIG_COMPAT
if (test_thread_flag(TIF_32BIT)) {
extern void do_signal32(sigset_t *, struct pt_regs *,
struct signal_deliver_cookie *);
do_signal32(oldset, regs, &cookie);
int restart_syscall,
unsigned long orig_i0);
do_signal32(oldset, regs, restart_syscall, orig_i0);
return;
}
#endif
signr = get_signal_to_deliver(&info, &ka, regs, &cookie);
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
/* If the debugger messes with the program counter, it clears
* the software "in syscall" bit, directing us to not perform
* a syscall restart.
*/
if (restart_syscall && !pt_regs_is_syscall(regs))
restart_syscall = 0;
if (signr > 0) {
if (cookie.restart_syscall)
syscall_restart(cookie.orig_i0, regs, &ka.sa);
if (restart_syscall)
syscall_restart(orig_i0, regs, &ka.sa);
handle_signal(signr, &ka, &info, oldset, regs);
/* a signal was successfully delivered; the saved
@ -568,16 +575,16 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
clear_thread_flag(TIF_RESTORE_SIGMASK);
return;
}
if (cookie.restart_syscall &&
if (restart_syscall &&
(regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
regs->u_regs[UREG_I0] == ERESTARTSYS ||
regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
/* replay the system call when we are done */
regs->u_regs[UREG_I0] = cookie.orig_i0;
regs->u_regs[UREG_I0] = orig_i0;
regs->tpc -= 4;
regs->tnpc -= 4;
}
if (cookie.restart_syscall &&
if (restart_syscall &&
regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
regs->u_regs[UREG_G1] = __NR_restart_syscall;
regs->tpc -= 4;
@ -598,26 +605,3 @@ void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0, unsigned long
if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
do_signal(regs, orig_i0);
}
void ptrace_signal_deliver(struct pt_regs *regs, void *cookie)
{
struct signal_deliver_cookie *cp = cookie;
if (cp->restart_syscall &&
(regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
regs->u_regs[UREG_I0] == ERESTARTSYS ||
regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
/* replay the system call when we are done */
regs->u_regs[UREG_I0] = cp->orig_i0;
regs->tpc -= 4;
regs->tnpc -= 4;
cp->restart_syscall = 0;
}
if (cp->restart_syscall &&
regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
regs->u_regs[UREG_G1] = __NR_restart_syscall;
regs->tpc -= 4;
regs->tnpc -= 4;
cp->restart_syscall = 0;
}
}

26
arch/sparc64/kernel/signal32.c
View file

@ -269,7 +269,7 @@ void do_sigreturn32(struct pt_regs *regs)
regs->tstate |= psr_to_tstate_icc(psr);
/* Prevent syscall restart. */
pt_regs_clear_trap_type(regs);
pt_regs_clear_syscall(regs);
err |= __get_user(fpu_save, &sf->fpu_save);
if (fpu_save)
@ -355,7 +355,7 @@ asmlinkage void do_rt_sigreturn32(struct pt_regs *regs)
regs->tstate |= psr_to_tstate_icc(psr);
/* Prevent syscall restart. */
pt_regs_clear_trap_type(regs);
pt_regs_clear_syscall(regs);
err |= __get_user(fpu_save, &sf->fpu_save);
if (fpu_save)
@ -768,16 +768,24 @@ static inline void syscall_restart32(unsigned long orig_i0, struct pt_regs *regs
* mistake.
*/
void do_signal32(sigset_t *oldset, struct pt_regs * regs,
struct signal_deliver_cookie *cookie)
int restart_syscall, unsigned long orig_i0)
{
struct k_sigaction ka;
siginfo_t info;
int signr;
signr = get_signal_to_deliver(&info, &ka, regs, cookie);
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
/* If the debugger messes with the program counter, it clears
* the "in syscall" bit, directing us to not perform a syscall
* restart.
*/
if (restart_syscall && !pt_regs_is_syscall(regs))
restart_syscall = 0;
if (signr > 0) {
if (cookie->restart_syscall)
syscall_restart32(cookie->orig_i0, regs, &ka.sa);
if (restart_syscall)
syscall_restart32(orig_i0, regs, &ka.sa);
handle_signal32(signr, &ka, &info, oldset, regs);
/* a signal was successfully delivered; the saved
@ -789,16 +797,16 @@ void do_signal32(sigset_t *oldset, struct pt_regs * regs,
clear_thread_flag(TIF_RESTORE_SIGMASK);
return;
}
if (cookie->restart_syscall &&
if (restart_syscall &&
(regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
regs->u_regs[UREG_I0] == ERESTARTSYS ||
regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
/* replay the system call when we are done */
regs->u_regs[UREG_I0] = cookie->orig_i0;
regs->u_regs[UREG_I0] = orig_i0;
regs->tpc -= 4;
regs->tnpc -= 4;
}
if (cookie->restart_syscall &&
if (restart_syscall &&
regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
regs->u_regs[UREG_G1] = __NR_restart_syscall;
regs->tpc -= 4;

1
include/asm-sparc/psr.h
View file

@ -25,6 +25,7 @@
#define PSR_PIL 0x00000f00 /* processor interrupt level */
#define PSR_EF 0x00001000 /* enable floating point */
#define PSR_EC 0x00002000 /* enable co-processor */
#define PSR_SYSCALL 0x00004000 /* inside of a syscall */
#define PSR_LE 0x00008000 /* SuperSparcII little-endian */
#define PSR_ICC 0x00f00000 /* integer condition codes */
#define PSR_C 0x00100000 /* carry bit */

10
include/asm-sparc/ptrace.h
View file

@ -39,6 +39,16 @@ struct pt_regs {
#define UREG_FP UREG_I6
#define UREG_RETPC UREG_I7
static inline bool pt_regs_is_syscall(struct pt_regs *regs)
{
return (regs->psr & PSR_SYSCALL);
}
static inline bool pt_regs_clear_syscall(struct pt_regs *regs)
{
return (regs->psr &= ~PSR_SYSCALL);
}
/* A register window */
struct reg_window {
unsigned long locals[8];

8
include/asm-sparc/signal.h
View file

@ -199,13 +199,7 @@ typedef struct sigaltstack {
size_t ss_size;
} stack_t;
struct sparc_deliver_cookie {
int restart_syscall;
unsigned long orig_i0;
};
struct pt_regs;
extern void ptrace_signal_deliver(struct pt_regs *regs, void *cookie);
#define ptrace_signal_deliver(regs, cookie) do { } while (0)
#endif /* !(__KERNEL__) */

2
include/asm-sparc64/psrcompat.h
View file

@ -12,6 +12,7 @@
#define PSR_PIL 0x00000f00 /* processor interrupt level */
#define PSR_EF 0x00001000 /* enable floating point */
#define PSR_EC 0x00002000 /* enable co-processor */
#define PSR_SYSCALL 0x00004000 /* inside of a syscall */
#define PSR_LE 0x00008000 /* SuperSparcII little-endian */
#define PSR_ICC 0x00f00000 /* integer condition codes */
#define PSR_C 0x00100000 /* carry bit */
@ -30,6 +31,7 @@ static inline unsigned int tstate_to_psr(unsigned long tstate)
PSR_S |
((tstate & TSTATE_ICC) >> 12) |
((tstate & TSTATE_XCC) >> 20) |
((tstate & TSTATE_SYSCALL) ? PSR_SYSCALL : 0) |
PSR_V8PLUS);
}

1
include/asm-sparc64/pstate.h
View file

@ -62,6 +62,7 @@
#define TSTATE_PRIV _AC(0x0000000000000400,UL) /* Privilege. */
#define TSTATE_IE _AC(0x0000000000000200,UL) /* Interrupt Enable. */
#define TSTATE_AG _AC(0x0000000000000100,UL) /* Alternate Globals.*/
#define TSTATE_SYSCALL _AC(0x0000000000000020,UL) /* in syscall trap */
#define TSTATE_CWP _AC(0x000000000000001f,UL) /* Curr Win-Pointer. */
/* Floating-Point Registers State Register.

12
include/asm-sparc64/ptrace.h
View file

@ -42,16 +42,14 @@ static inline int pt_regs_trap_type(struct pt_regs *regs)
return regs->magic & 0x1ff;
}
static inline int pt_regs_clear_trap_type(struct pt_regs *regs)
{
return regs->magic &= ~0x1ff;
}
static inline bool pt_regs_is_syscall(struct pt_regs *regs)
{
int tt = pt_regs_trap_type(regs);
return (regs->tstate & TSTATE_SYSCALL);
}
return (tt == 0x110 || tt == 0x111 || tt == 0x16d);
static inline bool pt_regs_clear_syscall(struct pt_regs *regs)
{
return (regs->tstate &= ~TSTATE_SYSCALL);
}
struct pt_regs32 {

8
include/asm-sparc64/signal.h
View file

@ -186,13 +186,7 @@ struct k_sigaction {
void __user *ka_restorer;
};
struct signal_deliver_cookie {
int restart_syscall;
unsigned long orig_i0;
};
struct pt_regs;
extern void ptrace_signal_deliver(struct pt_regs *regs, void *cookie);
#define ptrace_signal_deliver(regs, cookie) do { } while (0)
#endif /* !(__KERNEL__) */

7
include/asm-sparc64/ttable.h
View file

@ -91,13 +91,14 @@
nop;
#define SYSCALL_TRAP(routine, systbl) \
rdpr %pil, %g2; \
mov TSTATE_SYSCALL, %g3; \
sethi %hi(109f), %g7; \
ba,pt %xcc, etrap; \
ba,pt %xcc, etrap_syscall; \
109: or %g7, %lo(109b), %g7; \
sethi %hi(systbl), %l7; \
ba,pt %xcc, routine; \
or %l7, %lo(systbl), %l7; \
nop; nop;
or %l7, %lo(systbl), %l7;
#define TRAP_UTRAP(handler,lvl) \
mov handler, %g3; \