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powerpc/fsl: Flush the branch predictor at each kernel entry (64bit)

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Diana Craciun 2018-12-12 16:03:05 +02:00 committed by Michael Ellerman
parent f633a8ad63
commit 10c5e83afd
3 changed files with 37 additions and 1 deletions
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5
arch/powerpc/kernel/entry_64.S
View File

@ -80,6 +80,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM)
std r0,GPR0(r1)
std r10,GPR1(r1)
beq 2f /* if from kernel mode */
#ifdef CONFIG_PPC_FSL_BOOK3E
START_BTB_FLUSH_SECTION
BTB_FLUSH(r10)
END_BTB_FLUSH_SECTION
#endif
ACCOUNT_CPU_USER_ENTRY(r13, r10, r11)
2: std r2,GPR2(r1)
std r3,GPR3(r1)

26
arch/powerpc/kernel/exceptions-64e.S
View File

@ -296,7 +296,8 @@ ret_from_mc_except:
andi. r10,r11,MSR_PR; /* save stack pointer */ \
beq 1f; /* branch around if supervisor */ \
ld r1,PACAKSAVE(r13); /* get kernel stack coming from usr */\
1: cmpdi cr1,r1,0; /* check if SP makes sense */ \
1: type##_BTB_FLUSH \
cmpdi cr1,r1,0; /* check if SP makes sense */ \
bge- cr1,exc_##n##_bad_stack;/* bad stack (TODO: out of line) */ \
mfspr r10,SPRN_##type##_SRR0; /* read SRR0 before touching stack */
@ -328,6 +329,29 @@ ret_from_mc_except:
#define SPRN_MC_SRR0 SPRN_MCSRR0
#define SPRN_MC_SRR1 SPRN_MCSRR1
#ifdef CONFIG_PPC_FSL_BOOK3E
#define GEN_BTB_FLUSH \
START_BTB_FLUSH_SECTION \
beq 1f; \
BTB_FLUSH(r10) \
1: \
END_BTB_FLUSH_SECTION
#define CRIT_BTB_FLUSH \
START_BTB_FLUSH_SECTION \
BTB_FLUSH(r10) \
END_BTB_FLUSH_SECTION
#define DBG_BTB_FLUSH CRIT_BTB_FLUSH
#define MC_BTB_FLUSH CRIT_BTB_FLUSH
#define GDBELL_BTB_FLUSH GEN_BTB_FLUSH
#else
#define GEN_BTB_FLUSH
#define CRIT_BTB_FLUSH
#define DBG_BTB_FLUSH
#define GDBELL_BTB_FLUSH
#endif
#define NORMAL_EXCEPTION_PROLOG(n, intnum, addition) \
EXCEPTION_PROLOG(n, intnum, GEN, addition##_GEN(n))

7
arch/powerpc/mm/tlb_low_64e.S
View File

@ -70,6 +70,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
std r15,EX_TLB_R15(r12)
std r10,EX_TLB_CR(r12)
#ifdef CONFIG_PPC_FSL_BOOK3E
START_BTB_FLUSH_SECTION
mfspr r11, SPRN_SRR1
andi. r10,r11,MSR_PR
beq 1f
BTB_FLUSH(r10)
1:
END_BTB_FLUSH_SECTION
std r7,EX_TLB_R7(r12)
#endif
TLB_MISS_PROLOG_STATS