Commit e7956c92 authored by James Morse's avatar James Morse
Browse files

arm64: proton-pack: Expose whether the platform is mitigated by firmware 



is_spectre_bhb_fw_affected() allows the caller to determine if the CPU
is known to need a firmware mitigation. CPUs are either on the list
of CPUs we know about, or firmware has been queried and reported that
the platform is affected - and mitigated by firmware.

This helper is not useful to determine if the platform is mitigated
by firmware. A CPU could be on the know list, but the firmware may
not be implemented. Its affected but not mitigated.

spectre_bhb_enable_mitigation() handles this distinction by checking
the firmware state before enabling the mitigation.

Add a helper to expose this state. This will be used by the BPF JIT
to determine if calling firmware for a mitigation is necessary and
supported.

Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 63de8abd

arch/arm64/include/asm/spectre.h

+1 −0
Original line number Diff line number Diff line
@@ -97,6 +97,7 @@ enum mitigation_state arm64_get_meltdown_state(void); 


enum mitigation_state arm64_get_spectre_bhb_state(void);

bool is_spectre_bhb_affected(const struct arm64_cpu_capabilities *entry, int scope);

bool is_spectre_bhb_fw_mitigated(void);

void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *__unused);

bool try_emulate_el1_ssbs(struct pt_regs *regs, u32 instr);

arch/arm64/kernel/proton-pack.c

+5 −0
Original line number Diff line number Diff line
@@ -1094,6 +1094,11 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry) 
	update_mitigation_state(&spectre_bhb_state, state);

}



bool is_spectre_bhb_fw_mitigated(void)

{

	return test_bit(BHB_FW, &system_bhb_mitigations);

}



/* Patched to NOP when enabled */

void noinstr spectre_bhb_patch_loop_mitigation_enable(struct alt_instr *alt,

						     __le32 *origptr,