[PATCH 1/2] arm64: introduce separated bits for mm_context_t flags

[Yury Norov]

Currently mm->context.flags field uses thread_info flags which is not the best
idea for many reasons. For example, mm_context_t doesn't need most of 
thread_info
flags. And it would be difficult to add new mm-related flag if needed because it
may easily interfere with TIF ones.

To deal with it, the new MMCF_AARCH32 flag is introduced for mm_context_t flags,
where MMCF prefix stands for mm_context_t flags.

RFC: https://lkml.org/lkml/2017/7/31/454
v1:
 - changed the MMCF_AARCH32 bit number from 0x1 to 0x0 and added comment.

Signed-off-by: Yury Norov <yno...@caviumnetworks.com>
CC: Pratyush Anand <pan...@redhat.com>
CC: Catalin Marinas <catalin.mari...@arm.com>
---
 arch/arm64/include/asm/elf.h       | 4 ++--
 arch/arm64/include/asm/mmu.h       | 2 ++
 arch/arm64/kernel/probes/uprobes.c | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index acae781f7359..de11ed1484e3 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -139,7 +139,7 @@ typedef struct user_fpsimd_state elf_fpregset_t;
 
 #define SET_PERSONALITY(ex)                                            \
 ({                                                                     \
-       clear_bit(TIF_32BIT, &current->mm->context.flags);              \
+       clear_bit(MMCF_AARCH32, &current->mm->context.flags);           \
        clear_thread_flag(TIF_32BIT);                                   \
        current->personality &= ~READ_IMPLIES_EXEC;                     \
 })
@@ -195,7 +195,7 @@ typedef compat_elf_greg_t           
compat_elf_gregset_t[COMPAT_ELF_NGREG];
  */
 #define COMPAT_SET_PERSONALITY(ex)                                     \
 ({                                                                     \
-       set_bit(TIF_32BIT, &current->mm->context.flags);                \
+       set_bit(MMCF_AARCH32, &current->mm->context.flags);             \
        set_thread_flag(TIF_32BIT);                                     \
  })
 #define COMPAT_ARCH_DLINFO
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 5468c834b072..2c57b06b2883 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -16,6 +16,8 @@
 #ifndef __ASM_MMU_H
 #define __ASM_MMU_H
 
+#define MMCF_AARCH32   0x0     /* MM hosts AArch32 executables */
+
 typedef struct {
        atomic64_t      id;
        void            *vdso;
diff --git a/arch/arm64/kernel/probes/uprobes.c 
b/arch/arm64/kernel/probes/uprobes.c
index 26c998534dca..f29ef6b297e4 100644
--- a/arch/arm64/kernel/probes/uprobes.c
+++ b/arch/arm64/kernel/probes/uprobes.c
@@ -40,7 +40,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, 
struct mm_struct *mm,
        probe_opcode_t insn;
 
        /* TODO: Currently we do not support AARCH32 instruction probing */
-       if (test_bit(TIF_32BIT, &mm->context.flags))
+       if (test_bit(MMCF_AARCH32, &mm->context.flags))
                return -ENOTSUPP;
        else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
                return -EINVAL;
-- 
2.11.0