Commit 8f04e8e6 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3 



On CPUs with support for PSTATE.SSBS, the kernel can toggle the SSBD
state without needing to call into firmware.

This patch hooks into the existing SSBD infrastructure so that SSBS is
used on CPUs that support it, but it's all made horribly complicated by
the very real possibility of big/little systems that don't uniformly
provide the new capability.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 0bf0f444

arch/arm64/include/asm/processor.h

+7 −0
Original line number Diff line number Diff line
@@ -174,6 +174,10 @@ static inline void start_thread(struct pt_regs *regs, unsigned long pc, 
{

	start_thread_common(regs, pc);

	regs->pstate = PSR_MODE_EL0t;



	if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)

		regs->pstate |= PSR_SSBS_BIT;



	regs->sp = sp;

}
@@ -190,6 +194,9 @@ static inline void compat_start_thread(struct pt_regs *regs, unsigned long pc, 
	regs->pstate |= PSR_AA32_E_BIT;

#endif



	if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)

		regs->pstate |= PSR_AA32_SSBS_BIT;



	regs->compat_sp = sp;

}

#endif

arch/arm64/include/asm/ptrace.h

+1 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ 
#define PSR_AA32_I_BIT		0x00000080

#define PSR_AA32_A_BIT		0x00000100

#define PSR_AA32_E_BIT		0x00000200

#define PSR_AA32_SSBS_BIT	0x00800000

#define PSR_AA32_DIT_BIT	0x01000000

#define PSR_AA32_Q_BIT		0x08000000

#define PSR_AA32_V_BIT		0x10000000

arch/arm64/include/asm/sysreg.h

+3 −0
Original line number Diff line number Diff line
@@ -86,11 +86,14 @@ 


#define REG_PSTATE_PAN_IMM		sys_reg(0, 0, 4, 0, 4)

#define REG_PSTATE_UAO_IMM		sys_reg(0, 0, 4, 0, 3)

#define REG_PSTATE_SSBS_IMM		sys_reg(0, 3, 4, 0, 1)



#define SET_PSTATE_PAN(x) __emit_inst(0xd5000000 | REG_PSTATE_PAN_IMM |	\

				      (!!x)<<8 | 0x1f)

#define SET_PSTATE_UAO(x) __emit_inst(0xd5000000 | REG_PSTATE_UAO_IMM |	\

				      (!!x)<<8 | 0x1f)

#define SET_PSTATE_SSBS(x) __emit_inst(0xd5000000 | REG_PSTATE_SSBS_IMM | \

				       (!!x)<<8 | 0x1f)



#define SYS_DC_ISW			sys_insn(1, 0, 7, 6, 2)

#define SYS_DC_CSW			sys_insn(1, 0, 7, 10, 2)

arch/arm64/include/uapi/asm/ptrace.h

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
#define PSR_I_BIT	0x00000080

#define PSR_A_BIT	0x00000100

#define PSR_D_BIT	0x00000200

#define PSR_SSBS_BIT	0x00001000

#define PSR_PAN_BIT	0x00400000

#define PSR_UAO_BIT	0x00800000

#define PSR_V_BIT	0x10000000

arch/arm64/kernel/cpu_errata.c

+24 −2
Original line number Diff line number Diff line
@@ -312,6 +312,14 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt, 


void arm64_set_ssbd_mitigation(bool state)

{

	if (this_cpu_has_cap(ARM64_SSBS)) {

		if (state)

			asm volatile(SET_PSTATE_SSBS(0));

		else

			asm volatile(SET_PSTATE_SSBS(1));

		return;

	}



	switch (psci_ops.conduit) {

	case PSCI_CONDUIT_HVC:

		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_2, state, NULL);
@@ -336,6 +344,11 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, 


	WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());



	if (this_cpu_has_cap(ARM64_SSBS)) {

		required = false;

		goto out_printmsg;

	}



	if (psci_ops.smccc_version == SMCCC_VERSION_1_0) {

		ssbd_state = ARM64_SSBD_UNKNOWN;

		return false;
@@ -384,7 +397,6 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, 


	switch (ssbd_state) {

	case ARM64_SSBD_FORCE_DISABLE:

		pr_info_once("%s disabled from command-line\n", entry->desc);

		arm64_set_ssbd_mitigation(false);

		required = false;

		break;
@@ -397,7 +409,6 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, 
		break;



	case ARM64_SSBD_FORCE_ENABLE:

		pr_info_once("%s forced from command-line\n", entry->desc);

		arm64_set_ssbd_mitigation(true);

		required = true;

		break;
@@ -407,6 +418,17 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry, 
		break;

	}



out_printmsg:

	switch (ssbd_state) {

	case ARM64_SSBD_FORCE_DISABLE:

		pr_info_once("%s disabled from command-line\n", entry->desc);

		break;



	case ARM64_SSBD_FORCE_ENABLE:

		pr_info_once("%s forced from command-line\n", entry->desc);

		break;

	}



	return required;

}

#endif	/* CONFIG_ARM64_SSBD */

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