Re: [PATCH v8 4/6] arm64: cpufeature: Modify address authentication cpufeature to exact

Catalin Marinas
2020-09-14T10:23:49Z

On Mon, Sep 14, 2020 at 02:06:54PM +0530, Amit Daniel Kachhap wrote:
> 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 #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
>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> [Suzuki: Introduce new matching function for address authentication]
> Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

It looks fine to me.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>