From f4125cfdb3008363137f744c101e5d76ead760ba Mon Sep 17 00:00:00 2001 From: John David Anglin <dave.anglin@bell.net> Date: Fri, 28 Oct 2016 22:13:42 +0200 Subject: parisc: Avoid trashing sr2 and sr3 in LWS code There is no need to trash sr2 and sr3 in the Light-weight syscall (LWS). sr2 already points to kernel space (it's zero in userspace, otherwise syscalls wouldn't work), and since the LWS code is executed in userspace, we can simply ignore to preload sr3. Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de> --- arch/parisc/kernel/syscall.S | 53 ++++++++++++++++++++------------------------ 1 file changed, 24 insertions(+), 29 deletions(-) (limited to 'arch/parisc/kernel/syscall.S') diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index d03422e5f188..40190dbecdc0 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -474,11 +474,6 @@ lws_start: comiclr,>> __NR_lws_entries, %r20, %r0 b,n lws_exit_nosys - /* WARNING: Trashing sr2 and sr3 */ - mfsp %sr7,%r1 /* get userspace into sr3 */ - mtsp %r1,%sr3 - mtsp %r0,%sr2 /* get kernel space into sr2 */ - /* Load table start */ ldil L%lws_table, %r1 ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */ @@ -627,9 +622,9 @@ cas_action: stw %r1, 4(%sr2,%r20) #endif /* The load and store could fail */ -1: ldw,ma 0(%sr3,%r26), %r28 +1: ldw,ma 0(%r26), %r28 sub,<> %r28, %r25, %r0 -2: stw,ma %r24, 0(%sr3,%r26) +2: stw,ma %r24, 0(%r26) /* Free lock */ stw,ma %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG @@ -706,9 +701,9 @@ lws_compare_and_swap_2: nop /* 8bit load */ -4: ldb 0(%sr3,%r25), %r25 +4: ldb 0(%r25), %r25 b cas2_lock_start -5: ldb 0(%sr3,%r24), %r24 +5: ldb 0(%r24), %r24 nop nop nop @@ -716,9 +711,9 @@ lws_compare_and_swap_2: nop /* 16bit load */ -6: ldh 0(%sr3,%r25), %r25 +6: ldh 0(%r25), %r25 b cas2_lock_start -7: ldh 0(%sr3,%r24), %r24 +7: ldh 0(%r24), %r24 nop nop nop @@ -726,9 +721,9 @@ lws_compare_and_swap_2: nop /* 32bit load */ -8: ldw 0(%sr3,%r25), %r25 +8: ldw 0(%r25), %r25 b cas2_lock_start -9: ldw 0(%sr3,%r24), %r24 +9: ldw 0(%r24), %r24 nop nop nop @@ -737,14 +732,14 @@ lws_compare_and_swap_2: /* 64bit load */ #ifdef CONFIG_64BIT -10: ldd 0(%sr3,%r25), %r25 -11: ldd 0(%sr3,%r24), %r24 +10: ldd 0(%r25), %r25 +11: ldd 0(%r24), %r24 #else /* Load new value into r22/r23 - high/low */ -10: ldw 0(%sr3,%r25), %r22 -11: ldw 4(%sr3,%r25), %r23 +10: ldw 0(%r25), %r22 +11: ldw 4(%r25), %r23 /* Load new value into fr4 for atomic store later */ -12: flddx 0(%sr3,%r24), %fr4 +12: flddx 0(%r24), %fr4 #endif cas2_lock_start: @@ -794,30 +789,30 @@ cas2_action: ldo 1(%r0),%r28 /* 8bit CAS */ -13: ldb,ma 0(%sr3,%r26), %r29 +13: ldb,ma 0(%r26), %r29 sub,= %r29, %r25, %r0 b,n cas2_end -14: stb,ma %r24, 0(%sr3,%r26) +14: stb,ma %r24, 0(%r26) b cas2_end copy %r0, %r28 nop nop /* 16bit CAS */ -15: ldh,ma 0(%sr3,%r26), %r29 +15: ldh,ma 0(%r26), %r29 sub,= %r29, %r25, %r0 b,n cas2_end -16: sth,ma %r24, 0(%sr3,%r26) +16: sth,ma %r24, 0(%r26) b cas2_end copy %r0, %r28 nop nop /* 32bit CAS */ -17: ldw,ma 0(%sr3,%r26), %r29 +17: ldw,ma 0(%r26), %r29 sub,= %r29, %r25, %r0 b,n cas2_end -18: stw,ma %r24, 0(%sr3,%r26) +18: stw,ma %r24, 0(%r26) b cas2_end copy %r0, %r28 nop @@ -825,22 +820,22 @@ cas2_action: /* 64bit CAS */ #ifdef CONFIG_64BIT -19: ldd,ma 0(%sr3,%r26), %r29 +19: ldd,ma 0(%r26), %r29 sub,*= %r29, %r25, %r0 b,n cas2_end -20: std,ma %r24, 0(%sr3,%r26) +20: std,ma %r24, 0(%r26) copy %r0, %r28 #else /* Compare first word */ -19: ldw,ma 0(%sr3,%r26), %r29 +19: ldw,ma 0(%r26), %r29 sub,= %r29, %r22, %r0 b,n cas2_end /* Compare second word */ -20: ldw,ma 4(%sr3,%r26), %r29 +20: ldw,ma 4(%r26), %r29 sub,= %r29, %r23, %r0 b,n cas2_end /* Perform the store */ -21: fstdx %fr4, 0(%sr3,%r26) +21: fstdx %fr4, 0(%r26) copy %r0, %r28 #endif -- cgit v1.2.3 From 6ed518328d0189e0fdf1bb7c73290d546143ea66 Mon Sep 17 00:00:00 2001 From: John David Anglin <dave.anglin@bell.net> Date: Fri, 28 Oct 2016 23:00:34 -0400 Subject: parisc: Ensure consistent state when switching to kernel stack at syscall entry We have one critical section in the syscall entry path in which we switch from the userspace stack to kernel stack. In the event of an external interrupt, the interrupt code distinguishes between those two states by analyzing the value of sr7. If sr7 is zero, it uses the kernel stack. Therefore it's important, that the value of sr7 is in sync with the currently enabled stack. This patch now disables interrupts while executing the critical section. This prevents the interrupt handler to possibly see an inconsistent state which in the worst case can lead to crashes. Interestingly, in the syscall exit path interrupts were already disabled in the critical section which switches back to the userspace stack. Cc: <stable@vger.kernel.org> Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de> --- arch/parisc/kernel/syscall.S | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'arch/parisc/kernel/syscall.S') diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 40190dbecdc0..deec1f8465e5 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -106,8 +106,6 @@ linux_gateway_entry: mtsp %r0,%sr4 /* get kernel space into sr4 */ mtsp %r0,%sr5 /* get kernel space into sr5 */ mtsp %r0,%sr6 /* get kernel space into sr6 */ - mfsp %sr7,%r1 /* save user sr7 */ - mtsp %r1,%sr3 /* and store it in sr3 */ #ifdef CONFIG_64BIT /* for now we can *always* set the W bit on entry to the syscall @@ -133,6 +131,14 @@ linux_gateway_entry: depdi 0, 31, 32, %r21 1: #endif + + /* We use a rsm/ssm pair to prevent sr3 from being clobbered + * by external interrupts. + */ + mfsp %sr7,%r1 /* save user sr7 */ + rsm PSW_SM_I, %r0 /* disable interrupts */ + mtsp %r1,%sr3 /* and store it in sr3 */ + mfctl %cr30,%r1 xor %r1,%r30,%r30 /* ye olde xor trick */ xor %r1,%r30,%r1 @@ -147,6 +153,7 @@ linux_gateway_entry: */ mtsp %r0,%sr7 /* get kernel space into sr7 */ + ssm PSW_SM_I, %r0 /* enable interrupts */ STREGM %r1,FRAME_SIZE(%r30) /* save r1 (usp) here for now */ mfctl %cr30,%r1 /* get task ptr in %r1 */ LDREG TI_TASK(%r1),%r1 -- cgit v1.2.3 From 6a6e2a14bbc06a627acc71108808fdc866078db4 Mon Sep 17 00:00:00 2001 From: Helge Deller <deller@gmx.de> Date: Sat, 29 Oct 2016 23:52:43 +0200 Subject: parisc: Use LINUX_GATEWAY_ADDR define instead of hardcoded value LINUX_GATEWAY_ADDR is defined in unistd.h. Let's use it. Signed-off-by: Helge Deller <deller@gmx.de> --- arch/parisc/kernel/syscall.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/parisc/kernel/syscall.S') diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index deec1f8465e5..23de307c3052 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -100,7 +100,7 @@ set_thread_pointer: .endr /* This address must remain fixed at 0x100 for glibc's syscalls to work */ - .align 256 + .align LINUX_GATEWAY_ADDR linux_gateway_entry: gate .+8, %r0 /* become privileged */ mtsp %r0,%sr4 /* get kernel space into sr4 */ -- cgit v1.2.3