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| author | Amit Daniel Kachhap <amit.kachhap@arm.com> | 2020-09-14 14:06:53 +0530 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-09-14 12:07:02 +0100 |
| commit | e16aeb072682d3dcdbdad452c974baa0d2b0c6db (patch) | |
| tree | 20484ed8c1c59204ef50fb524fa206e6198e63f9 /arch/arm64/kernel/traps.c | |
| parent | 4ef333b2d10680b5d966a733ed7171f72164fcd5 (diff) | |
| download | linux-e16aeb072682d3dcdbdad452c974baa0d2b0c6db.tar.gz | |
arm64: ptrauth: Introduce Armv8.3 pointer authentication enhancements
Some Armv8.3 Pointer Authentication enhancements have been introduced
which are mandatory for Armv8.6 and optional for Armv8.3. These features
are,
* ARMv8.3-PAuth2 - An enhanced PAC generation logic is added which hardens
finding the correct PAC value of the authenticated pointer.
* ARMv8.3-FPAC - Fault is generated now when the ptrauth authentication
instruction fails in authenticating the PAC present in the address.
This is different from earlier case when such failures just adds an
error code in the top byte and waits for subsequent load/store to abort.
The ptrauth instructions which may cause this fault are autiasp, retaa
etc.
The above features are now represented by additional configurations
for the Address Authentication cpufeature and a new ESR exception class.
The userspace fault received in the kernel due to ARMv8.3-FPAC is treated
as Illegal instruction and hence signal SIGILL is injected with ILL_ILLOPN
as the signal code. Note that this is different from earlier ARMv8.3
ptrauth where signal SIGSEGV is issued due to Pointer authentication
failures. The in-kernel PAC fault causes kernel to crash.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Link: https://lore.kernel.org/r/20200914083656.21428-4-amit.kachhap@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/traps.c')
| -rw-r--r-- | arch/arm64/kernel/traps.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 29fd00fe94f2..b24f81197a68 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -479,6 +479,17 @@ void do_bti(struct pt_regs *regs) } NOKPROBE_SYMBOL(do_bti); +void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr) +{ + /* + * Unexpected FPAC exception or pointer authentication failure in + * the kernel: kill the task before it does any more harm. + */ + BUG_ON(!user_mode(regs)); + force_signal_inject(SIGILL, ILL_ILLOPN, regs->pc, esr); +} +NOKPROBE_SYMBOL(do_ptrauth_fault); + #define __user_cache_maint(insn, address, res) \ if (address >= user_addr_max()) { \ res = -EFAULT; \ @@ -775,6 +786,7 @@ static const char *esr_class_str[] = { [ESR_ELx_EC_SYS64] = "MSR/MRS (AArch64)", [ESR_ELx_EC_SVE] = "SVE", [ESR_ELx_EC_ERET] = "ERET/ERETAA/ERETAB", + [ESR_ELx_EC_FPAC] = "FPAC", [ESR_ELx_EC_IMP_DEF] = "EL3 IMP DEF", [ESR_ELx_EC_IABT_LOW] = "IABT (lower EL)", [ESR_ELx_EC_IABT_CUR] = "IABT (current EL)", |