Messages in this thread Patch in this message | | | From | Yury Norov <> | Subject | [PATCH RFC] arm64: introduce mm_context_t flags | Date | Mon, 31 Jul 2017 17:48:25 +0300 |
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Hi Pratyush, Catalin
In patch 06beb72fbe23e ("arm64: introduce mm context flag to keep 32 bit task information") you introduce the field flags but use it only for a single flag - TIF_32BIT. It looks hacky to me for three reasons: - The flag is introduced for the case where it's impossible to get the thread info structure for the thread associated with mm. So thread_info flags (TIF) may also be unavailable at place. This is not the case for the only existing user of if - uprobes, but in general this approach requires to include thread headers in mm code, which may become unwanted dependency. - New flag, if it uses TIF bits, for consistency should for example set/clear TIF_32BIT_AARCH64 for ILP32 tasks. And to be completely consistent, with current approach we'd mirror thread_info flags to mm_context flags. And keep it syncronized. - If we start using TIF flags here, we cannot easily add new mm_context specific bits because they may mess with TIF ones.
I think that this is not what was intended when you added new field in mm_context_t.
In this patch the MMCF_AARCH32 flag is introduced, where MMCF prefix stands for mm_context_t flags. And the new flag is used for uprobes code instead of TIF_32BIT.
Yury
Signed-off-by: Yury Norov <ynorov@caviumnetworks.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, ¤t->mm->context.flags); \ + clear_bit(MMCF_AARCH32, ¤t->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, ¤t->mm->context.flags); \ + set_bit(MMCF_AARCH32, ¤t->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..3ae24ed11ae3 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 0x1 + 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
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