pkey_sighandler_tests.c currently hardcodes x86 PKRU encodings. The
first step towards running those tests on arm64 is to abstract away
the pkey register values.
Since those tests want to deny access to all keys except a few,
we have each arch define PKEY_REG_ALLOW_NONE, the pkey register value
denying access to all keys. We then use the existing set_pkey_bits()
helper to grant access to specific keys.
Because pkeys may also remove the execute permission on arm64, we
need to be a little careful: all code is mapped with pkey 0, and we
need it to remain executable. pkey_reg_restrictive_default() is
introduced for that purpose: the value it returns prevents RW access
to all pkeys, but retains X permission for pkey 0.
test_pkru_preserved_after_sigusr1() only checks that the pkey
register value remains unchanged after a signal is delivered, so the
particular value is irrelevant. We enable pkey 0 and a few more
arbitrary keys in the smallest range available on all architectures
(8 keys on arm64).
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20241029144539.111155-5-kevin.brodsky@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The encoding of the pkey register differs on arm64, than on x86/ppc. On those
platforms, a bit in the register is used to disable permissions, for arm64, a
bit enabled in the register indicates that the permission is allowed.
This drops two asserts of the form:
assert(read_pkey_reg() <= orig_pkey_reg);
Because on arm64 this doesn't hold, due to the encoding.
The pkey must be reset to both access allow and write allow in the signal
handler. pkey_access_allow() works currently for PowerPC as the
PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE have overlapping bits set.
Access to the uc_mcontext is abstracted, as arm64 has a different structure.
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20240822151113.1479789-27-joey.gouly@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
