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From: Diana Craciun <diana.craciun@nxp.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Diana Craciun <diana.craciun@nxp.com>
Subject: [PATCH 07/11 v2] powerpc/fsl: Flush the branch predictor at each kernel entry (32 bit)
Date: Fri, 21 Dec 2018 19:30:33 +0200	[thread overview]
Message-ID: <1545413437-5538-8-git-send-email-diana.craciun@nxp.com> (raw)
In-Reply-To: <1545413437-5538-1-git-send-email-diana.craciun@nxp.com>

In order to protect against speculation attacks on
indirect branches, the branch predictor is flushed at
kernel entry to protect for the following situations:
- userspace process attacking another userspace process
- userspace process attacking the kernel
Basically when the privillege level change (i.e.the kernel
is entered), the branch predictor state is flushed.

Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
---
v1-->v2
- fixed warnings reported by the automated build system

 arch/powerpc/kernel/head_booke.h     | 11 +++++++++++
 arch/powerpc/kernel/head_fsl_booke.S | 15 +++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index d0862a1..27f5249 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -32,6 +32,15 @@
  */
 #define THREAD_NORMSAVE(offset)	(THREAD_NORMSAVES + (offset * 4))
 
+#ifdef CONFIG_PPC_FSL_BOOK3E
+#define BOOKE_CLEAR_BTB(reg)									\
+START_BTB_FLUSH_SECTION								\
+	BTB_FLUSH(reg)									\
+END_BTB_FLUSH_SECTION
+#else
+#define BOOKE_CLEAR_BTB(reg)
+#endif
+
 #define NORMAL_EXCEPTION_PROLOG(intno)						     \
 	mtspr	SPRN_SPRG_WSCRATCH0, r10;	/* save one register */	     \
 	mfspr	r10, SPRN_SPRG_THREAD;					     \
@@ -43,6 +52,7 @@
 	andi.	r11, r11, MSR_PR;	/* check whether user or kernel    */\
 	mr	r11, r1;						     \
 	beq	1f;							     \
+	BOOKE_CLEAR_BTB(r11)						\
 	/* if from user, start at top of this thread's kernel stack */       \
 	lwz	r11, THREAD_INFO-THREAD(r10);				     \
 	ALLOC_STACK_FRAME(r11, THREAD_SIZE);				     \
@@ -128,6 +138,7 @@
 	stw	r9,_CCR(r8);		/* save CR on stack		   */\
 	mfspr	r11,exc_level_srr1;	/* check whether user or kernel    */\
 	DO_KVM	BOOKE_INTERRUPT_##intno exc_level_srr1;		             \
+	BOOKE_CLEAR_BTB(r10)						\
 	andi.	r11,r11,MSR_PR;						     \
 	mfspr	r11,SPRN_SPRG_THREAD;	/* if from user, start at top of   */\
 	lwz	r11,THREAD_INFO-THREAD(r11); /* this thread's kernel stack */\
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index e2750b8..2386ce2 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -453,6 +453,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
 	mfcr	r13
 	stw	r13, THREAD_NORMSAVE(3)(r10)
 	DO_KVM	BOOKE_INTERRUPT_DTLB_MISS SPRN_SRR1
+START_BTB_FLUSH_SECTION
+	mfspr r11, SPRN_SRR1
+	andi. r10,r11,MSR_PR
+	beq 1f
+	BTB_FLUSH(r10)
+1:
+END_BTB_FLUSH_SECTION
 	mfspr	r10, SPRN_DEAR		/* Get faulting address */
 
 	/* If we are faulting a kernel address, we have to use the
@@ -547,6 +554,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
 	mfcr	r13
 	stw	r13, THREAD_NORMSAVE(3)(r10)
 	DO_KVM	BOOKE_INTERRUPT_ITLB_MISS SPRN_SRR1
+START_BTB_FLUSH_SECTION
+	mfspr r11, SPRN_SRR1
+	andi. r10,r11,MSR_PR
+	beq 1f
+	BTB_FLUSH(r10)
+1:
+END_BTB_FLUSH_SECTION
+
 	mfspr	r10, SPRN_SRR0		/* Get faulting address */
 
 	/* If we are faulting a kernel address, we have to use the
-- 
2.5.5


  parent reply	other threads:[~2018-12-21 17:47 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-21 17:30 [PATCH 00/11 v2] powerpc/fsl: NXP PowerPC Spectre variant 2 workarounds Diana Craciun
2018-12-21 17:30 ` [PATCH 01/11 v2] powerpc/fsl: Add infrastructure to fixup branch predictor flush Diana Craciun
2018-12-21 17:30 ` [PATCH 02/11 v2] powerpc/fsl: Add macro to flush the branch predictor Diana Craciun
2018-12-21 17:30 ` [PATCH 03/11 v2] powerpc/fsl: Fix spectre_v2 mitigations reporting Diana Craciun
2018-12-21 17:30 ` [PATCH 04/11 v2] powerpc/fsl: Emulate SPRN_BUCSR register Diana Craciun
2018-12-21 17:30 ` [PATCH 05/11 v2] powerpc/fsl: Add nospectre_v2 command line argument Diana Craciun
2018-12-21 17:30 ` [PATCH 06/11 v2] powerpc/fsl: Flush the branch predictor at each kernel entry (64bit) Diana Craciun
2018-12-21 17:30 ` Diana Craciun [this message]
2018-12-21 17:30 ` [PATCH 08/11 v2] powerpc/fsl: Flush branch predictor when entering KVM Diana Craciun
2018-12-21 17:30 ` [PATCH 09/11 v2] powerpc/fsl: Enable runtime patching if nospectre_v2 boot arg is used Diana Craciun
2018-12-21 17:30 ` [PATCH 10/11 v2] powerpc/fsl: Update Spectre v2 reporting Diana Craciun
2018-12-21 17:30 ` [PATCH 11/11 v2] powerpc/fsl: Add FSL_PPC_BOOK3E as supported arch for nospectre_v2 boot arg Diana Craciun
2018-12-22 10:07 ` [PATCH 00/11 v2] powerpc/fsl: NXP PowerPC Spectre variant 2 workarounds Michael Ellerman

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