iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arm64: proton-pack: Report Spectre-BHB vulnerabilities as part of Spectre-v2

Browse Source 
commit dee435be76f4117410bbd90573a881fd33488f37 upstream.

Speculation attacks against some high-performance processors can
make use of branch history to influence future speculation as part of
a spectre-v2 attack. This is not mitigated by CSV2, meaning CPUs that
previously reported 'Not affected' are now moderately mitigated by CSV2.

Update the value in /sys/devices/system/cpu/vulnerabilities/spectre_v2
to also show the state of the BHB mitigation.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[ code move to cpu_errata.c for backport ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
James Morse 2022-03-15 18:24:11 +00:00 committed by Greg Kroah-Hartman
parent c45d885c5a
commit 1b735c8dc1
2 changed files with 46 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/arm64/include/asm/cpufeature.h
View File

@ -639,6 +639,15 @@ static inline int arm64_get_ssbd_state(void)
void arm64_set_ssbd_mitigation(bool state);
/* Watch out, ordering is important here. */
enum mitigation_state {
SPECTRE_UNAFFECTED,
SPECTRE_MITIGATED,
SPECTRE_VULNERABLE,
};
enum mitigation_state arm64_get_spectre_bhb_state(void);
extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)

41
arch/arm64/kernel/cpu_errata.c
View File

@ -989,15 +989,41 @@ ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
return sprintf(buf, "Mitigation: __user pointer sanitization\n");
}
static const char *get_bhb_affected_string(enum mitigation_state bhb_state)
{
switch (bhb_state) {
case SPECTRE_UNAFFECTED:
return "";
default:
case SPECTRE_VULNERABLE:
return ", but not BHB";
case SPECTRE_MITIGATED:
return ", BHB";
}
}
ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
char *buf)
{
enum mitigation_state bhb_state = arm64_get_spectre_bhb_state();
const char *bhb_str = get_bhb_affected_string(bhb_state);
const char *v2_str = "Branch predictor hardening";
switch (get_spectre_v2_workaround_state()) {
case ARM64_BP_HARDEN_NOT_REQUIRED:
return sprintf(buf, "Not affected\n");
case ARM64_BP_HARDEN_WA_NEEDED:
return sprintf(buf, "Mitigation: Branch predictor hardening\n");
case ARM64_BP_HARDEN_UNKNOWN:
if (bhb_state == SPECTRE_UNAFFECTED)
return sprintf(buf, "Not affected\n");
/*
* Platforms affected by Spectre-BHB can't report
* "Not affected" for Spectre-v2.
*/
v2_str = "CSV2";
fallthrough;
case ARM64_BP_HARDEN_WA_NEEDED:
return sprintf(buf, "Mitigation: %s%s\n", v2_str, bhb_str);
case ARM64_BP_HARDEN_UNKNOWN:
fallthrough;
default:
return sprintf(buf, "Vulnerable\n");
}
@ -1019,3 +1045,10 @@ ssize_t cpu_show_spec_store_bypass(struct device *dev,
return sprintf(buf, "Vulnerable\n");
}
static enum mitigation_state spectre_bhb_state;
enum mitigation_state arm64_get_spectre_bhb_state(void)
{
return spectre_bhb_state;
}