From: Will Deacon <will.deacon@xxxxxxx>
[ Upstream commit bd4fb6d270bc423a9a4098108784f7f9254c4e6d ]
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.deacon@xxxxxxx>
[ Mark: fixup conflicts ]
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
---
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 | 6 ++++++
arch/arm64/include/asm/uaccess.h | 3 +--
arch/arm64/include/uapi/asm/hwcap.h | 1 +
arch/arm64/kernel/cpufeature.c | 12 ++++++++++++
arch/arm64/kernel/cpuinfo.c | 1 +
8 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index fc3d26c954a40..efabe6c476aa0 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -133,6 +133,19 @@
hint #22
.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 822a9192c5511..f66bb04fdf2dd 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -34,6 +34,10 @@
#define psb_csync() asm volatile("hint #17" : : : "memory")
#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 61fd28522d74f..a7e2378df3d1c 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -56,7 +56,8 @@
#define ARM64_WORKAROUND_1542419 35
#define ARM64_SPECTRE_BHB 36
#define ARM64_WORKAROUND_1742098 37
+#define ARM64_HAS_SB 38
-#define ARM64_NCAPS 38
+#define ARM64_NCAPS 39
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 0a8342de5796a..8f015c20f3e0e 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -97,6 +97,11 @@
#define SET_PSTATE_SSBS(x) __emit_inst(0xd5000000 | REG_PSTATE_SSBS_IMM | \
(!!x)<<8 | 0x1f)
+#define __SYS_BARRIER_INSN(CRm, op2, Rt) \
+ __emit_inst(0xd5000000 | sys_insn(0, 3, 3, (CRm), (op2)) | ((Rt) & 0x1f))
+
+#define SB_BARRIER_INSN __SYS_BARRIER_INSN(0, 7, 31)
+
#define SYS_DC_ISW sys_insn(1, 0, 7, 6, 2)
#define SYS_DC_IGSW sys_insn(1, 0, 7, 6, 4)
#define SYS_DC_IGDSW sys_insn(1, 0, 7, 6, 6)
@@ -528,6 +533,7 @@
#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
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index e66b0fca99c2f..3c3bf4171f3b6 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -46,8 +46,7 @@ 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();
/* On user-mode return, check fs is correct */
set_thread_flag(TIF_FSCHECK);
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index 2bcd6e4f34740..7784f7cba16cf 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -49,5 +49,6 @@
#define HWCAP_ILRCPC (1 << 26)
#define HWCAP_FLAGM (1 << 27)
#define HWCAP_SSBS (1 << 28)
+#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 d7e73a7963d1b..3f6a2187d0911 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -144,6 +144,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
+ ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_SB_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_LRCPC_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_FCMA_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_JSCVT_SHIFT, 4, 0),
@@ -1361,6 +1362,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.cpu_enable = cpu_enable_ssbs,
},
#endif
+ {
+ .desc = "Speculation barrier (SB)",
+ .capability = ARM64_HAS_SB,
+ .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+ .matches = has_cpuid_feature,
+ .sys_reg = SYS_ID_AA64ISAR1_EL1,
+ .field_pos = ID_AA64ISAR1_SB_SHIFT,
+ .sign = FTR_UNSIGNED,
+ .min_field_value = 1,
+ },
{},
};
@@ -1415,6 +1426,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FCMA_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FCMA),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_LRCPC),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 2, CAP_HWCAP, HWCAP_ILRCPC),
+ HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_SB_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_SB),
HWCAP_CAP(SYS_ID_AA64MMFR2_EL1, ID_AA64MMFR2_AT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_USCAT),
#ifdef CONFIG_ARM64_SVE
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_SVE_SHIFT, FTR_UNSIGNED, ID_AA64PFR0_SVE, CAP_HWCAP, HWCAP_SVE),
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 36bd58d8ca11f..9d013e7106a99 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -82,6 +82,7 @@ static const char *const hwcap_str[] = {
"ilrcpc",
"flagm",
"ssbs",
+ "sb",
NULL
};
--
2.30.2
