This is a note to let you know that I've just added the patch titled
powerpc/tm: Abort on emulation and alignment faults
to the 3.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-tm-abort-on-emulation-and-alignment-faults.patch
and it can be found in the queue-3.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6ce6c629fd8254b3177650de99699682ff7f6707 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey@xxxxxxxxxxx>
Date: Sun, 26 May 2013 18:09:39 +0000
Subject: powerpc/tm: Abort on emulation and alignment faults
From: Michael Neuling <mikey@xxxxxxxxxxx>
commit 6ce6c629fd8254b3177650de99699682ff7f6707 upstream.
If we are emulating an instruction inside an active user transaction that
touches memory, the kernel can't emulate it as it operates in transactional
suspend context. We need to abort these transactions and send them back to
userspace for the hardware to rollback.
We can service these if the user transaction is in suspend mode, since the
kernel will operate in the same suspend context.
This adds a check to all alignment faults and to specific instruction
emulations (only string instructions for now). If the user process is in an
active (non-suspended) transaction, we abort the transaction go back to
userspace allowing the HW to roll back the transaction and tell the user of the
failure. This also adds new tm abort cause codes to report the reason of the
persistent error to the user.
Crappy test case here http://neuling.org/devel/junkcode/aligntm.c
Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/powerpc/transactional_memory.txt | 7 ++++--
arch/powerpc/include/asm/reg.h | 2 +
arch/powerpc/kernel/traps.c | 29 +++++++++++++++++++++++++
3 files changed, 36 insertions(+), 2 deletions(-)
--- a/Documentation/powerpc/transactional_memory.txt
+++ b/Documentation/powerpc/transactional_memory.txt
@@ -180,9 +180,12 @@ kernel aborted a transaction:
transactions for consistency will use this.
TM_CAUSE_SIGNAL Signal delivered.
TM_CAUSE_MISC Currently unused.
+ TM_CAUSE_ALIGNMENT Alignment fault.
+ TM_CAUSE_EMULATE Emulation that touched memory.
-These can be checked by the user program's abort handler as TEXASR[0:7].
-
+These can be checked by the user program's abort handler as TEXASR[0:7]. If
+bit 7 is set, it indicates that the error is consider persistent. For example
+a TM_CAUSE_ALIGNMENT will be persistent while a TM_CAUSE_RESCHED will not.q
GDB
===
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -122,6 +122,8 @@
#define TM_CAUSE_SYSCALL 0xd8 /* future use */
#define TM_CAUSE_MISC 0xd6 /* future use */
#define TM_CAUSE_SIGNAL 0xd4
+#define TM_CAUSE_ALIGNMENT 0xd2
+#define TM_CAUSE_EMULATE 0xd0
#if defined(CONFIG_PPC_BOOK3S_64)
#define MSR_64BIT MSR_SF
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -52,6 +52,7 @@
#ifdef CONFIG_PPC64
#include <asm/firmware.h>
#include <asm/processor.h>
+#include <asm/tm.h>
#endif
#include <asm/kexec.h>
#include <asm/ppc-opcode.h>
@@ -913,6 +914,28 @@ static int emulate_isel(struct pt_regs *
return 0;
}
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+static inline bool tm_abort_check(struct pt_regs *regs, int cause)
+{
+ /* If we're emulating a load/store in an active transaction, we cannot
+ * emulate it as the kernel operates in transaction suspended context.
+ * We need to abort the transaction. This creates a persistent TM
+ * abort so tell the user what caused it with a new code.
+ */
+ if (MSR_TM_TRANSACTIONAL(regs->msr)) {
+ tm_enable();
+ tm_abort(cause);
+ return true;
+ }
+ return false;
+}
+#else
+static inline bool tm_abort_check(struct pt_regs *regs, int reason)
+{
+ return false;
+}
+#endif
+
static int emulate_instruction(struct pt_regs *regs)
{
u32 instword;
@@ -952,6 +975,9 @@ static int emulate_instruction(struct pt
/* Emulate load/store string insn. */
if ((instword & PPC_INST_STRING_GEN_MASK) == PPC_INST_STRING) {
+ if (tm_abort_check(regs,
+ TM_CAUSE_EMULATE | TM_CAUSE_PERSISTENT))
+ return -EINVAL;
PPC_WARN_EMULATED(string, regs);
return emulate_string_inst(regs, instword);
}
@@ -1124,6 +1150,9 @@ void alignment_exception(struct pt_regs
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
+ if (tm_abort_check(regs, TM_CAUSE_ALIGNMENT | TM_CAUSE_PERSISTENT))
+ goto bail;
+
/* we don't implement logging of alignment exceptions */
if (!(current->thread.align_ctl & PR_UNALIGN_SIGBUS))
fixed = fix_alignment(regs);
Patches currently in stable-queue which might be from mikey@xxxxxxxxxxx are
queue-3.9/powerpc-tm-abort-on-emulation-and-alignment-faults.patch
queue-3.9/powerpc-tm-fix-userspace-stack-corruption-on-signal-delivery-for-active-transactions.patch
queue-3.9/powerpc-tm-update-cause-codes-documentation.patch
queue-3.9/powerpc-tm-make-room-for-hypervisor-in-abort-cause-codes.patch
queue-3.9/powerpc-tm-move-tm-abort-cause-codes-to-uapi.patch
--
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