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selftests/x86/lam: Add malloc and tag-bits test cases for linear-address masking

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LAM is supported only in 64-bit mode and applies only addresses used for data
accesses. In 64-bit mode, linear address have 64 bits. LAM is applied to 64-bit
linear address and allow software to use high bits for metadata.
LAM supports configurations that differ regarding which pointer bits are masked
and can be used for metadata.

LAM includes following mode:

 - LAM_U57, pointer bits in positions 62:57 are masked (LAM width 6),
   allows bits 62:57 of a user pointer to be used as metadata.

There are some arch_prctls:
ARCH_ENABLE_TAGGED_ADDR: enable LAM mode, mask high bits of a user pointer.
ARCH_GET_UNTAG_MASK: get current untagged mask.
ARCH_GET_MAX_TAG_BITS: the maximum tag bits user can request. zero if LAM
is not supported.

The LAM mode is for pre-process, a process has only one chance to set LAM mode.
But there is no API to disable LAM mode. So all of test cases are run under
child process.

Functions of this test:

MALLOC

 - LAM_U57 masks bits 57:62 of a user pointer. Process on user space
   can dereference such pointers.

 - Disable LAM, dereference a pointer with metadata above 48 bit or 57 bit
   lead to trigger SIGSEGV.

TAG_BITS

 - Max tag bits of LAM_U57 is 6.

Signed-off-by: Weihong Zhang <weihong.zhang@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20230312112612.31869-13-kirill.shutemov%40linux.intel.com
This commit is contained in:
Weihong Zhang
2023-03-12 14:26:07 +03:00
committed by Dave Hansen
parent 23e5d9ec2b
commit 3de9745c12
2 changed files with 327 additions and 1 deletions
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tools/testing/selftests/x86/Makefile
+1 -1
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@@ -18,7 +18,7 @@ TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering \
corrupt_xstate_header amx
corrupt_xstate_header amx lam
# Some selftests require 32bit support enabled also on 64bit systems
TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall