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arm64: cpufeature: Modify address authentication cpufeature to exact
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The current address authentication cpufeature levels are set as LOWER_SAFE
which is not compatible with the different configurations added for Armv8.3
ptrauth enhancements as the different levels have different behaviour and
there is no tunable to enable the lower safe versions. This is rectified
by setting those cpufeature type as EXACT.

The current cpufeature framework also does not interfere in the booting of
non-exact secondary cpus but rather marks them as tainted. As a workaround
this is fixed by replacing the generic match handler with a new handler
specific to ptrauth.

After this change, if there is any variation in ptrauth configurations in
secondary cpus from boot cpu then those mismatched cpus are parked in an
infinite loop.

Following ptrauth crash log is observed in Arm fastmodel with simulated
mismatched cpus without this fix,

 CPU features: SANITY CHECK: Unexpected variation in SYS_ID_AA64ISAR1_EL1. Boot CPU: 0x11111110211402, CPU4: 0x11111110211102
 CPU features: Unsupported CPU feature variation detected.
 GICv3: CPU4: found redistributor 100 region 0:0x000000002f180000
 CPU4: Booted secondary processor 0x0000000100 [0x410fd0f0]
 Unable to handle kernel paging request at virtual address bfff800010dadf3c
 Mem abort info:
   ESR = 0x86000004
   EC = 0x21: IABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
 [bfff800010dadf3c] address between user and kernel address ranges
 Internal error: Oops: 86000004 [#1] PREEMPT SMP
 Modules linked in:
 CPU: 4 PID: 29 Comm: migration/4 Tainted: G S                5.8.0-rc4-00005-ge658591d66d1-dirty torvalds#158
 Hardware name: Foundation-v8A (DT)
 pstate: 60000089 (nZCv daIf -PAN -UAO BTYPE=--)
 pc : 0xbfff800010dadf3c
 lr : __schedule+0x2b4/0x5a8
 sp : ffff800012043d70
 x29: ffff800012043d70 x28: 0080000000000000
 x27: ffff800011cbe000 x26: ffff00087ad37580
 x25: ffff00087ad37000 x24: ffff800010de7d50
 x23: ffff800011674018 x22: 0784800010dae2a8
 x21: ffff00087ad37000 x20: ffff00087acb8000
 x19: ffff00087f742100 x18: 0000000000000030
 x17: 0000000000000000 x16: 0000000000000000
 x15: ffff800011ac1000 x14: 00000000000001bd
 x13: 0000000000000000 x12: 0000000000000000
 x11: 0000000000000000 x10: 71519a147ddfeb82
 x9 : 825d5ec0fb246314 x8 : ffff00087ad37dd8
 x7 : 0000000000000000 x6 : 00000000fffedb0e
 x5 : 00000000ffffffff x4 : 0000000000000000
 x3 : 0000000000000028 x2 : ffff80086e11e000
 x1 : ffff00087ad37000 x0 : ffff00087acdc600
 Call trace:
  0xbfff800010dadf3c
  schedule+0x78/0x110
  schedule_preempt_disabled+0x24/0x40
  __kthread_parkme+0x68/0xd0
  kthread+0x138/0x160
  ret_from_fork+0x10/0x34
 Code: bad PC value

After this fix, the mismatched CPU4 is parked as,
 CPU features: CPU4: Detected conflict for capability 39 (Address authentication (IMP DEF algorithm)), System: 1, CPU: 0
 CPU4: will not boot
 CPU4: failed to come online
 CPU4: died during early boot

[Suzuki: Introduce new matching function for address authentication]

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200914083656.21428-5-amit.kachhap@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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@amitdanielkachhap @willdeacon
amitdanielkachhap authored and willdeacon committed Sep 14, 2020
1 parent e16aeb0 commit ba9d1d3
Showing 1 changed file with 35 additions and 9 deletions.
44 changes: 35 additions & 9 deletions arch/arm64/kernel/cpufeature.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -197,9 +197,9 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
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),
ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_API_SHIFT, 4, 0),
FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_API_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_APA_SHIFT, 4, 0),
FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_APA_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_DPB_SHIFT, 4, 0),
ARM64_FTR_END,
};
Expand Down Expand Up @@ -1648,11 +1648,37 @@ static void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused)
#endif /* CONFIG_ARM64_RAS_EXTN */

#ifdef CONFIG_ARM64_PTR_AUTH
static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
int __unused)
static bool has_address_auth_cpucap(const struct arm64_cpu_capabilities *entry, int scope)
{
return __system_matches_cap(ARM64_HAS_ADDRESS_AUTH_ARCH) ||
__system_matches_cap(ARM64_HAS_ADDRESS_AUTH_IMP_DEF);
int boot_val, sec_val;

/* We don't expect to be called with SCOPE_SYSTEM */
WARN_ON(scope == SCOPE_SYSTEM);
/*
* The ptr-auth feature levels are not intercompatible with lower
* levels. Hence we must match ptr-auth feature level of the secondary
* CPUs with that of the boot CPU. The level of boot cpu is fetched
* from the sanitised register whereas direct register read is done for
* the secondary CPUs.
* The sanitised feature state is guaranteed to match that of the
* boot CPU as a mismatched secondary CPU is parked before it gets
* a chance to update the state, with the capability.
*/
boot_val = cpuid_feature_extract_field(read_sanitised_ftr_reg(entry->sys_reg),
entry->field_pos, entry->sign);
if (scope & SCOPE_BOOT_CPU)
return boot_val >= entry->min_field_value;
/* Now check for the secondary CPUs with SCOPE_LOCAL_CPU scope */
sec_val = cpuid_feature_extract_field(__read_sysreg_by_encoding(entry->sys_reg),
entry->field_pos, entry->sign);
return sec_val == boot_val;
}

static bool has_address_auth_metacap(const struct arm64_cpu_capabilities *entry,
int scope)
{
return has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_ARCH], scope) ||
has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_IMP_DEF], scope);
}

static bool has_generic_auth(const struct arm64_cpu_capabilities *entry,
Expand Down Expand Up @@ -2021,7 +2047,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.sign = FTR_UNSIGNED,
.field_pos = ID_AA64ISAR1_APA_SHIFT,
.min_field_value = ID_AA64ISAR1_APA_ARCHITECTED,
.matches = has_cpuid_feature,
.matches = has_address_auth_cpucap,
},
{
.desc = "Address authentication (IMP DEF algorithm)",
Expand All @@ -2031,12 +2057,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.sign = FTR_UNSIGNED,
.field_pos = ID_AA64ISAR1_API_SHIFT,
.min_field_value = ID_AA64ISAR1_API_IMP_DEF,
.matches = has_cpuid_feature,
.matches = has_address_auth_cpucap,
},
{
.capability = ARM64_HAS_ADDRESS_AUTH,
.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
.matches = has_address_auth,
.matches = has_address_auth_metacap,
},
{
.desc = "Generic authentication (architected algorithm)",
Expand Down

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