signal/syscall/swapcontext fixes
Paul Mackerras
paulus at samba.org
Tue Mar 7 23:32:28 EST 2006
Here is the current set of changes I have for fixing various problems
and potential problems I found in the syscall entry/exit code.
Briefly, the changes are:
* The TIF_SAVE_NVGPRS mechanism was only being used by swapcontext, so
I removed it and put swapcontext back the way it was in 2.6.15, with
an assembler stub to save the non-volatile GPRs before calling the C
code. The save_general_regs functions now WARN_ON(!FULL_REGS(regs)).
* 32-bit wasn't testing the _TIF_NOERROR bit in the syscall fast exit
path, so it was only doing anything with it once it saw some other
bit being set.
* 32-bit wasn't doing the call to ptrace_notify in the syscall exit
path when the _TIF_SINGLESTEP bit was set.
* _TIF_RESTOREALL was in both _TIF_USER_WORK_MASK and
_TIF_PERSYSCALL_MASK, which is odd since _TIF_RESTOREALL is only set
by system calls. I took it out of _TIF_USER_WORK_MASK.
* On 64-bit, _TIF_RESTOREALL wasn't causing the non-volatile registers
to be restored (unless perhaps a signal was delivered or the syscall
was traced or single-stepped). Thus the non-volatile registers
weren't restored on exit from a signal handler. We probably got
away with it mostly because signal handlers written in C wouldn't
alter the non-volatile registers.
* On 32-bit I simplified the code and made it more like 64-bit by
making the syscall exit path jump to ret_from_except to handle
preemption and signal delivery.
* 32-bit was calling do_signal unnecessarily when _TIF_RESTOREALL was
set - but I think because of that 32-bit was actually restoring the
non-volatile registers on exit from a signal handler.
* I changed the order of enabling interrupts and saving the
non-volatile registers before calling do_syscall_trace_leave; now we
enable interrupts first.
Any comments before I send this off to Linus to go in 2.6.16?
Paul.
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 840aad4..c9a660e 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -92,7 +92,6 @@ int main(void)
DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count));
- DEFINE(TI_SIGFRAME, offsetof(struct thread_info, nvgprs_frame));
DEFINE(TI_TASK, offsetof(struct thread_info, task));
#ifdef CONFIG_PPC32
DEFINE(TI_EXECDOMAIN, offsetof(struct thread_info, exec_domain));
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index f20a672..4827ca1 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -227,7 +227,7 @@ ret_from_syscall:
MTMSRD(r10)
lwz r9,TI_FLAGS(r12)
li r8,-_LAST_ERRNO
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_RESTORE_SIGMASK)
+ andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
bne- syscall_exit_work
cmplw 0,r3,r8
blt+ syscall_exit_cont
@@ -287,8 +287,10 @@ syscall_dotrace:
syscall_exit_work:
andi. r0,r9,_TIF_RESTOREALL
- bne- 2f
- cmplw 0,r3,r8
+ beq+ 0f
+ REST_NVGPRS(r1)
+ b 2f
+0: cmplw 0,r3,r8
blt+ 1f
andi. r0,r9,_TIF_NOERROR
bne- 1f
@@ -302,9 +304,7 @@ syscall_exit_work:
2: andi. r0,r9,(_TIF_PERSYSCALL_MASK)
beq 4f
- /* Clear per-syscall TIF flags if any are set, but _leave_
- _TIF_SAVE_NVGPRS set in r9 since we haven't dealt with that
- yet. */
+ /* Clear per-syscall TIF flags if any are set. */
li r11,_TIF_PERSYSCALL_MASK
addi r12,r12,TI_FLAGS
@@ -318,8 +318,13 @@ syscall_exit_work:
subi r12,r12,TI_FLAGS
4: /* Anything which requires enabling interrupts? */
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SAVE_NVGPRS)
- beq 7f
+ andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
+ beq ret_from_except
+
+ /* Re-enable interrupts */
+ ori r10,r10,MSR_EE
+ SYNC
+ MTMSRD(r10)
/* Save NVGPRS if they're not saved already */
lwz r4,_TRAP(r1)
@@ -328,71 +333,11 @@ syscall_exit_work:
SAVE_NVGPRS(r1)
li r4,0xc00
stw r4,_TRAP(r1)
-
- /* Re-enable interrupts */
-5: ori r10,r10,MSR_EE
- SYNC
- MTMSRD(r10)
-
- andi. r0,r9,_TIF_SAVE_NVGPRS
- bne save_user_nvgprs
-
-save_user_nvgprs_cont:
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
- beq 7f
-
+5:
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_syscall_trace_leave
- REST_NVGPRS(r1)
-
-6: lwz r3,GPR3(r1)
- LOAD_MSR_KERNEL(r10,MSR_KERNEL) /* doesn't include MSR_EE */
- SYNC
- MTMSRD(r10) /* disable interrupts again */
- rlwinm r12,r1,0,0,(31-THREAD_SHIFT) /* current_thread_info() */
- lwz r9,TI_FLAGS(r12)
-7:
- andi. r0,r9,_TIF_NEED_RESCHED
- bne 8f
- lwz r5,_MSR(r1)
- andi. r5,r5,MSR_PR
- beq ret_from_except
- andi. r0,r9,_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK
- beq ret_from_except
- b do_user_signal
-8:
- ori r10,r10,MSR_EE
- SYNC
- MTMSRD(r10) /* re-enable interrupts */
- bl schedule
- b 6b
-
-save_user_nvgprs:
- lwz r8,TI_SIGFRAME(r12)
-
-.macro savewords start, end
- 1: stw \start,4*(\start)(r8)
- .section __ex_table,"a"
- .align 2
- .long 1b,save_user_nvgprs_fault
- .previous
- .if \end - \start
- savewords "(\start+1)",\end
- .endif
-.endm
- savewords 14,31
- b save_user_nvgprs_cont
-
-
-save_user_nvgprs_fault:
- li r3,11 /* SIGSEGV */
- lwz r4,TI_TASK(r12)
- bl force_sigsegv
+ b ret_from_except_full
- rlwinm r12,r1,0,0,(31-THREAD_SHIFT) /* current_thread_info() */
- lwz r9,TI_FLAGS(r12)
- b save_user_nvgprs_cont
-
#ifdef SHOW_SYSCALLS
do_show_syscall:
#ifdef SHOW_SYSCALLS_TASK
@@ -490,6 +435,14 @@ ppc_clone:
stw r0,_TRAP(r1) /* register set saved */
b sys_clone
+ .globl ppc_swapcontext
+ppc_swapcontext:
+ SAVE_NVGPRS(r1)
+ lwz r0,_TRAP(r1)
+ rlwinm r0,r0,0,0,30 /* clear LSB to indicate full */
+ stw r0,_TRAP(r1) /* register set saved */
+ b sys_swapcontext
+
/*
* Top-level page fault handling.
* This is in assembler because if do_page_fault tells us that
@@ -683,7 +636,7 @@ user_exc_return: /* r10 contains MSR_KE
/* Check current_thread_info()->flags */
rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
lwz r9,TI_FLAGS(r9)
- andi. r0,r9,(_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_RESTORE_SIGMASK)
+ andi. r0,r9,(_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK|_TIF_NEED_RESCHED)
bne do_work
restore_user:
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 388f861..24be0cf 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -160,7 +160,7 @@ syscall_exit:
mtmsrd r10,1
ld r9,TI_FLAGS(r12)
li r11,-_LAST_ERRNO
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_RESTOREALL|_TIF_SAVE_NVGPRS|_TIF_NOERROR|_TIF_RESTORE_SIGMASK)
+ andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
bne- syscall_exit_work
cmpld r3,r11
ld r5,_CCR(r1)
@@ -216,8 +216,10 @@ syscall_exit_work:
If TIF_NOERROR is set, just save r3 as it is. */
andi. r0,r9,_TIF_RESTOREALL
- bne- 2f
- cmpld r3,r11 /* r10 is -LAST_ERRNO */
+ beq+ 0f
+ REST_NVGPRS(r1)
+ b 2f
+0: cmpld r3,r11 /* r10 is -LAST_ERRNO */
blt+ 1f
andi. r0,r9,_TIF_NOERROR
bne- 1f
@@ -229,9 +231,7 @@ syscall_exit_work:
2: andi. r0,r9,(_TIF_PERSYSCALL_MASK)
beq 4f
- /* Clear per-syscall TIF flags if any are set, but _leave_
- _TIF_SAVE_NVGPRS set in r9 since we haven't dealt with that
- yet. */
+ /* Clear per-syscall TIF flags if any are set. */
li r11,_TIF_PERSYSCALL_MASK
addi r12,r12,TI_FLAGS
@@ -240,10 +240,9 @@ syscall_exit_work:
stdcx. r10,0,r12
bne- 3b
subi r12,r12,TI_FLAGS
-
-4: bl .save_nvgprs
- /* Anything else left to do? */
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP|_TIF_SAVE_NVGPRS)
+
+4: /* Anything else left to do? */
+ andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
beq .ret_from_except_lite
/* Re-enable interrupts */
@@ -251,26 +250,10 @@ syscall_exit_work:
ori r10,r10,MSR_EE
mtmsrd r10,1
- andi. r0,r9,_TIF_SAVE_NVGPRS
- bne save_user_nvgprs
-
- /* If tracing, re-enable interrupts and do it */
-save_user_nvgprs_cont:
- andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
- beq 5f
-
+ bl .save_nvgprs
addi r3,r1,STACK_FRAME_OVERHEAD
bl .do_syscall_trace_leave
- REST_NVGPRS(r1)
- clrrdi r12,r1,THREAD_SHIFT
-
- /* Disable interrupts again and handle other work if any */
-5: mfmsr r10
- rldicl r10,r10,48,1
- rotldi r10,r10,16
- mtmsrd r10,1
-
- b .ret_from_except_lite
+ b .ret_from_except
/* Save non-volatile GPRs, if not already saved. */
_GLOBAL(save_nvgprs)
@@ -282,51 +265,6 @@ _GLOBAL(save_nvgprs)
std r0,_TRAP(r1)
blr
-
-save_user_nvgprs:
- ld r10,TI_SIGFRAME(r12)
- andi. r0,r9,_TIF_32BIT
- beq- save_user_nvgprs_64
-
- /* 32-bit save to userspace */
-
-.macro savewords start, end
- 1: stw \start,4*(\start)(r10)
- .section __ex_table,"a"
- .align 3
- .llong 1b,save_user_nvgprs_fault
- .previous
- .if \end - \start
- savewords "(\start+1)",\end
- .endif
-.endm
- savewords 14,31
- b save_user_nvgprs_cont
-
-save_user_nvgprs_64:
- /* 64-bit save to userspace */
-
-.macro savelongs start, end
- 1: std \start,8*(\start)(r10)
- .section __ex_table,"a"
- .align 3
- .llong 1b,save_user_nvgprs_fault
- .previous
- .if \end - \start
- savelongs "(\start+1)",\end
- .endif
-.endm
- savelongs 14,31
- b save_user_nvgprs_cont
-
-save_user_nvgprs_fault:
- li r3,11 /* SIGSEGV */
- ld r4,TI_TASK(r12)
- bl .force_sigsegv
-
- clrrdi r12,r1,THREAD_SHIFT
- ld r9,TI_FLAGS(r12)
- b save_user_nvgprs_cont
/*
* The sigsuspend and rt_sigsuspend system calls can call do_signal
@@ -352,6 +290,16 @@ _GLOBAL(ppc_clone)
bl .sys_clone
b syscall_exit
+_GLOBAL(ppc32_swapcontext)
+ bl .save_nvgprs
+ bl .compat_sys_swapcontext
+ b syscall_exit
+
+_GLOBAL(ppc64_swapcontext)
+ bl .save_nvgprs
+ bl .sys_swapcontext
+ b syscall_exit
+
_GLOBAL(ret_from_fork)
bl .schedule_tail
REST_NVGPRS(r1)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 400793c..bcb8357 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -561,10 +561,7 @@ void do_syscall_trace_leave(struct pt_re
regs->result);
if ((test_thread_flag(TIF_SYSCALL_TRACE)
-#ifdef CONFIG_PPC64
- || test_thread_flag(TIF_SINGLESTEP)
-#endif
- )
+ || test_thread_flag(TIF_SINGLESTEP))
&& (current->ptrace & PT_PTRACED))
do_syscall_trace();
}
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index bd837b5..d7a4e81 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -151,10 +151,7 @@ static inline int save_general_regs(stru
elf_greg_t64 *gregs = (elf_greg_t64 *)regs;
int i;
- if (!FULL_REGS(regs)) {
- set_thread_flag(TIF_SAVE_NVGPRS);
- current_thread_info()->nvgprs_frame = frame->mc_gregs;
- }
+ WARN_ON(!FULL_REGS(regs));
for (i = 0; i <= PT_RESULT; i ++) {
if (i == 14 && !FULL_REGS(regs))
@@ -215,15 +212,7 @@ static inline int get_old_sigaction(stru
static inline int save_general_regs(struct pt_regs *regs,
struct mcontext __user *frame)
{
- if (!FULL_REGS(regs)) {
- /* Zero out the unsaved GPRs to avoid information
- leak, and set TIF_SAVE_NVGPRS to ensure that the
- registers do actually get saved later. */
- memset(®s->gpr[14], 0, 18 * sizeof(unsigned long));
- current_thread_info()->nvgprs_frame = &frame->mc_gregs;
- set_thread_flag(TIF_SAVE_NVGPRS);
- }
-
+ WARN_ON(!FULL_REGS(regs));
return __copy_to_user(&frame->mc_gregs, regs, GP_REGS_SIZE);
}
@@ -826,8 +815,8 @@ static int do_setcontext(struct ucontext
}
long sys_swapcontext(struct ucontext __user *old_ctx,
- struct ucontext __user *new_ctx,
- int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
+ struct ucontext __user *new_ctx,
+ int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
{
unsigned char tmp;
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 497a5d3..4324f8a 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -118,14 +118,7 @@ static long setup_sigcontext(struct sigc
err |= __put_user(0, &sc->v_regs);
#endif /* CONFIG_ALTIVEC */
err |= __put_user(&sc->gp_regs, &sc->regs);
- if (!FULL_REGS(regs)) {
- /* Zero out the unsaved GPRs to avoid information
- leak, and set TIF_SAVE_NVGPRS to ensure that the
- registers do actually get saved later. */
- memset(®s->gpr[14], 0, 18 * sizeof(unsigned long));
- set_thread_flag(TIF_SAVE_NVGPRS);
- current_thread_info()->nvgprs_frame = &sc->gp_regs;
- }
+ WARN_ON(!FULL_REGS(regs));
err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
err |= __copy_to_user(&sc->fp_regs, ¤t->thread.fpr, FP_REGS_SIZE);
err |= __put_user(signr, &sc->signal);
diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.S
index 8a9f994..1ad55f0 100644
--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.S
@@ -288,7 +288,7 @@ COMPAT_SYS(clock_settime)
COMPAT_SYS(clock_gettime)
COMPAT_SYS(clock_getres)
COMPAT_SYS(clock_nanosleep)
-COMPAT_SYS(swapcontext)
+SYSX(ppc64_swapcontext,ppc32_swapcontext,ppc_swapcontext)
COMPAT_SYS(tgkill)
COMPAT_SYS(utimes)
COMPAT_SYS(statfs64)
diff --git a/include/asm-powerpc/thread_info.h b/include/asm-powerpc/thread_info.h
index 237fc2b..ffc7462 100644
--- a/include/asm-powerpc/thread_info.h
+++ b/include/asm-powerpc/thread_info.h
@@ -37,7 +37,6 @@ struct thread_info {
int preempt_count; /* 0 => preemptable,
<0 => BUG */
struct restart_block restart_block;
- void __user *nvgprs_frame;
/* low level flags - has atomic operations done on it */
unsigned long flags ____cacheline_aligned_in_smp;
};
@@ -120,7 +119,6 @@ static inline struct thread_info *curren
#define TIF_MEMDIE 10
#define TIF_SECCOMP 11 /* secure computing */
#define TIF_RESTOREALL 12 /* Restore all regs (implies NOERROR) */
-#define TIF_SAVE_NVGPRS 13 /* Save r14-r31 in signal frame */
#define TIF_NOERROR 14 /* Force successful syscall return */
#define TIF_RESTORE_SIGMASK 15 /* Restore signal mask in do_signal */
@@ -137,15 +135,13 @@ static inline struct thread_info *curren
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
#define _TIF_RESTOREALL (1<<TIF_RESTOREALL)
-#define _TIF_SAVE_NVGPRS (1<<TIF_SAVE_NVGPRS)
#define _TIF_NOERROR (1<<TIF_NOERROR)
#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP)
#define _TIF_USER_WORK_MASK (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | \
- _TIF_NEED_RESCHED | _TIF_RESTOREALL | \
- _TIF_RESTORE_SIGMASK)
-#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR|_TIF_SAVE_NVGPRS)
+ _TIF_NEED_RESCHED | _TIF_RESTORE_SIGMASK)
+#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)
#endif /* __KERNEL__ */
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