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| author | Mark Rutland <mark.rutland@arm.com> | 2018-12-07 18:39:26 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2018-12-13 16:42:46 +0000 |
| commit | ec6e822d1a22d0eef1d1fa260dff751dba9a4258 (patch) | |
| tree | 709322a7fd3dcaa397913e2fbd46f912d19ec9df /arch/arm64/kernel/ptrace.c | |
| parent | 7503197562567b57ec14feb3a9d5400ebc56812f (diff) | |
| download | linux-ec6e822d1a22d0eef1d1fa260dff751dba9a4258.tar.bz2 | |
arm64: expose user PAC bit positions via ptrace
When pointer authentication is in use, data/instruction pointers have a
number of PAC bits inserted into them. The number and position of these
bits depends on the configured TCR_ELx.TxSZ and whether tagging is
enabled. ARMv8.3 allows tagging to differ for instruction and data
pointers.
For userspace debuggers to unwind the stack and/or to follow pointer
chains, they need to be able to remove the PAC bits before attempting to
use a pointer.
This patch adds a new structure with masks describing the location of
the PAC bits in userspace instruction and data pointers (i.e. those
addressable via TTBR0), which userspace can query via PTRACE_GETREGSET.
By clearing these bits from pointers (and replacing them with the value
of bit 55), userspace can acquire the PAC-less versions.
This new regset is exposed when the kernel is built with (user) pointer
authentication support, and the address authentication feature is
enabled. Otherwise, the regset is hidden.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
[will: Fix to use vabits_user instead of VA_BITS and rename macro]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/ptrace.c')
| -rw-r--r-- | arch/arm64/kernel/ptrace.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 1710a2d01669..9dce33b0e260 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -46,6 +46,7 @@ #include <asm/debug-monitors.h> #include <asm/fpsimd.h> #include <asm/pgtable.h> +#include <asm/pointer_auth.h> #include <asm/stacktrace.h> #include <asm/syscall.h> #include <asm/traps.h> @@ -956,6 +957,30 @@ out: #endif /* CONFIG_ARM64_SVE */ +#ifdef CONFIG_ARM64_PTR_AUTH +static int pac_mask_get(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + void *kbuf, void __user *ubuf) +{ + /* + * The PAC bits can differ across data and instruction pointers + * depending on TCR_EL1.TBID*, which we may make use of in future, so + * we expose separate masks. + */ + unsigned long mask = ptrauth_user_pac_mask(); + struct user_pac_mask uregs = { + .data_mask = mask, + .insn_mask = mask, + }; + + if (!system_supports_address_auth()) + return -EINVAL; + + return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &uregs, 0, -1); +} +#endif /* CONFIG_ARM64_PTR_AUTH */ + enum aarch64_regset { REGSET_GPR, REGSET_FPR, @@ -968,6 +993,9 @@ enum aarch64_regset { #ifdef CONFIG_ARM64_SVE REGSET_SVE, #endif +#ifdef CONFIG_ARM64_PTR_AUTH + REGSET_PAC_MASK, +#endif }; static const struct user_regset aarch64_regsets[] = { @@ -1037,6 +1065,16 @@ static const struct user_regset aarch64_regsets[] = { .get_size = sve_get_size, }, #endif +#ifdef CONFIG_ARM64_PTR_AUTH + [REGSET_PAC_MASK] = { + .core_note_type = NT_ARM_PAC_MASK, + .n = sizeof(struct user_pac_mask) / sizeof(u64), + .size = sizeof(u64), + .align = sizeof(u64), + .get = pac_mask_get, + /* this cannot be set dynamically */ + }, +#endif }; static const struct user_regset_view user_aarch64_view = { |