From: Will Deacon <will.dea...@arm.com>
commit bd4fb6d270bc423a9a4098108784f7f9254c4e6d upstream
We currently use a DSB; ISB sequence to inhibit speculation in set_fs().
Whilst this works for current CPUs, future CPUs may implement a new SB
barrier instruction which acts as an architected speculation barrier.
On CPUs that support it, patch in an SB; NOP sequence over the DSB; ISB
sequence and advertise the presence of the new instruction to userspace.
Signed-off-by: Will Deacon <will.dea...@arm.com>
[florian:
- adjust number capabilities
- wire decoding of ftr_id_aa64_isar1
- __emit_inst -> __inst_arm
- sys_insn -> sys_reg]
Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
---
arch/arm64/include/asm/assembler.h | 13 +++++++++++++
arch/arm64/include/asm/barrier.h | 4 ++++
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/include/asm/sysreg.h | 13 +++++++++++++
arch/arm64/include/asm/uaccess.h | 3 +--
arch/arm64/include/uapi/asm/hwcap.h | 1 +
arch/arm64/kernel/cpufeature.c | 22 +++++++++++++++++++++-
arch/arm64/kernel/cpuinfo.c | 1 +
8 files changed, 56 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h
b/arch/arm64/include/asm/assembler.h
index 3f85bbcd7e40..0f689aa0b300 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -95,6 +95,19 @@
.endm
/*
+ * Speculation barrier
+ */
+ .macro sb
+alternative_if_not ARM64_HAS_SB
+ dsb nsh
+ isb
+alternative_else
+ SB_BARRIER_INSN
+ nop
+alternative_endif
+ .endm
+
+/*
* Sanitise a 64-bit bounded index wrt speculation, returning zero if out
* of bounds.
*/
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 0b0755c961ac..159329160fb4 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -33,6 +33,10 @@
#define csdb() asm volatile("hint #20" : : : "memory")
+#define spec_bar() asm volatile(ALTERNATIVE("dsb nsh\nisb\n",
\
+ SB_BARRIER_INSN"nop\n",
\
+ ARM64_HAS_SB))
+
#define mb() dsb(sy)
#define rmb() dsb(ld)
#define wmb() dsb(st)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 8c7c4b23a8b1..8a25f6e39f3a 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -38,7 +38,8 @@
#define ARM64_HARDEN_BRANCH_PREDICTOR 17
#define ARM64_SSBD 18
#define ARM64_MISMATCHED_CACHE_TYPE 19
+#define ARM64_HAS_SB 20
-#define ARM64_NCAPS 20
+#define ARM64_NCAPS 21
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 88bbe364b6ae..1c49eaac1938 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -86,6 +86,12 @@
#define SET_PSTATE_UAO(x) __inst_arm(0xd5000000 | REG_PSTATE_UAO_IMM |\
(!!x)<<8 | 0x1f)
+#define __SYS_BARRIER_INSN(CRm, op2, Rt) \
+ __inst_arm(0xd5000000 | sys_reg(0, 3, 3, (CRm), (op2)) | ((Rt) & 0x1f))
+
+#define SB_BARRIER_INSN __SYS_BARRIER_INSN(0, 7, 31)
+
+
/* Common SCTLR_ELx flags. */
#define SCTLR_ELx_EE (1 << 25)
#define SCTLR_ELx_I (1 << 12)
@@ -116,6 +122,13 @@
#define ID_AA64ISAR0_SHA1_SHIFT 8
#define ID_AA64ISAR0_AES_SHIFT 4
+/* id_aa64isar1 */
+#define ID_AA64ISAR1_SB_SHIFT 36
+#define ID_AA64ISAR1_LRCPC_SHIFT 20
+#define ID_AA64ISAR1_FCMA_SHIFT 16
+#define ID_AA64ISAR1_JSCVT_SHIFT 12
+#define ID_AA64ISAR1_DPB_SHIFT 0
+
/* id_aa64pfr0 */
#define ID_AA64PFR0_CSV3_SHIFT 60
#define ID_AA64PFR0_CSV2_SHIFT 56
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index f5cd96c60eb9..195323089e5a 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -71,8 +71,7 @@ static inline void set_fs(mm_segment_t fs)
* Prevent a mispredicted conditional call to set_fs from forwarding
* the wrong address limit to access_ok under speculation.
*/
- dsb(nsh);
- isb();
+ spec_bar();
/*
* Enable/disable UAO so that copy_to_user() etc can access
diff --git a/arch/arm64/include/uapi/asm/hwcap.h
b/arch/arm64/include/uapi/asm/hwcap.h
index a739287ef6a3..3aa659624968 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -30,5 +30,6 @@
#define HWCAP_ATOMICS (1 << 8)
#define HWCAP_FPHP (1 << 9)
#define HWCAP_ASIMDHP (1 << 10)
+#define HWCAP_SB (1 << 29)
#endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 8cf001baee21..1a5879c0b711 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -93,6 +93,15 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
ARM64_FTR_END,
};
+static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
+ ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_SB_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_LRCPC_SHIFT, 4,
0),
+ ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_FCMA_SHIFT, 4,
0),
+ ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_JSCVT_SHIFT, 4,
0),
+ ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_DPB_SHIFT, 4,
0),
+ ARM64_FTR_END,
+};
+
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT,
4, 0),
ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV2_SHIFT,
4, 0),
@@ -326,7 +335,7 @@ static const struct __ftr_reg_entry {
/* Op1 = 0, CRn = 0, CRm = 6 */
ARM64_FTR_REG(SYS_ID_AA64ISAR0_EL1, ftr_id_aa64isar0),
- ARM64_FTR_REG(SYS_ID_AA64ISAR1_EL1, ftr_aa64raz),
+ ARM64_FTR_REG(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1),
/* Op1 = 0, CRn = 0, CRm = 7 */
ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
@@ -949,6 +958,16 @@ static const struct arm64_cpu_capabilities
arm64_features[] = {
.enable = kpti_install_ng_mappings,
},
#endif
+ {
+ .desc = "Speculation barrier (SB)",
+ .capability = ARM64_HAS_SB,
+ .def_scope = SCOPE_SYSTEM,
+ .matches = has_cpuid_feature,
+ .sys_reg = SYS_ID_AA64ISAR1_EL1,
+ .field_pos = ID_AA64ISAR1_SB_SHIFT,
+ .sign = FTR_UNSIGNED,
+ .min_field_value = 1,
+ },
{},
};
@@ -976,6 +995,7 @@ static const struct arm64_cpu_capabilities
arm64_elf_hwcaps[] = {
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 1,
CAP_HWCAP, HWCAP_FPHP),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 0,
CAP_HWCAP, HWCAP_ASIMD),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 1,
CAP_HWCAP, HWCAP_ASIMDHP),
+ HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_SB_SHIFT, FTR_UNSIGNED, 1,
CAP_HWCAP, HWCAP_SB),
{},
};
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index b3d5b3e8fbcb..5de2d55a999e 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -63,6 +63,7 @@ static const char *const hwcap_str[] = {
"atomics",
"fphp",
"asimdhp",
+ "sb",
NULL
};
--
2.7.4
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
