From ec6e822d1a22d0eef1d1fa260dff751dba9a4258 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Fri, 7 Dec 2018 18:39:26 +0000 Subject: 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 Signed-off-by: Mark Rutland Signed-off-by: Kristina Martsenko Cc: Catalin Marinas Cc: Ramana Radhakrishnan Cc: Will Deacon [will: Fix to use vabits_user instead of VA_BITS and rename macro] Signed-off-by: Will Deacon --- arch/arm64/include/uapi/asm/ptrace.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/arm64/include/uapi') diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index a36227fdb084..c2f249bcd829 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h @@ -229,6 +229,13 @@ struct user_sve_header { SVE_PT_SVE_OFFSET + SVE_PT_SVE_SIZE(vq, flags) \ : SVE_PT_FPSIMD_OFFSET + SVE_PT_FPSIMD_SIZE(vq, flags)) +/* pointer authentication masks (NT_ARM_PAC_MASK) */ + +struct user_pac_mask { + __u64 data_mask; + __u64 insn_mask; +}; + #endif /* __ASSEMBLY__ */ #endif /* _UAPI__ASM_PTRACE_H */ -- cgit v1.2.3-55-g7522