This patchset is the result of discussion:
https://lkml.org/lkml/2017/7/31/454
First patch introduces MMCF flags for mm_context_t ->flags to separate it from
TIF ones. And second patch moves personality-related setup code from
SET_PERSONALITY() to the helper.
Yury Norov (2):
arm64: introduce separated bits for mm_context_t flags
arm64: cleanup {COMPAT_,}SET_PERSONALITY() macro
arch/arm64/include/asm/elf.h | 7 +++++--
arch/arm64/include/asm/mmu.h | 2 ++
arch/arm64/include/asm/thread_info.h | 3 +++
arch/arm64/kernel/probes/uprobes.c | 2 +-
arch/arm64/kernel/process.c | 8 ++++++++
5 files changed, 19 insertions(+), 3 deletions(-)
--
2.11.0
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.
Also, mm_context_t flag doesn't require atomicity and ordering of the
access, so using set/clear_bit() is replaced with simple masks.
RFC: https://lkml.org/lkml/2017/7/31/454
v1:
- changed the MMCF_AARCH32 bit number from 0x1 to 0x0 and added comment
v2:
- using set/clear_bit() is replaced with simple masks.
Signed-off-by: Yury Norov <[email protected]>
---
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 3288c2b36731..517b9ff0456c 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); \
+ current->mm->context.flags = 0; \
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); \
+ current->mm->context.flags = MMCF_AARCH32; \
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..e4c474c6501e 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 /* 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..636ca0119c0e 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 (mm->context.flags & MMCF_AARCH32)
return -ENOTSUPP;
else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
return -EINVAL;
--
2.11.0
There is some work that should be done after setting the personality.
Currently it's done in the macro, which is not the best idea.
In this patch new arch_setup_new_exec() routine is introduced, and all
setup code is moved there, as suggested by Catalin:
https://lkml.org/lkml/2017/8/4/494
v2:
- don't move clearing READ_IMPLIES_EXEC flag from SET_PERSONALITY()
Signed-off-by: Yury Norov <[email protected]>
CC: Pratyush Anand <[email protected]>
CC: Catalin Marinas <[email protected]>
---
arch/arm64/include/asm/elf.h | 7 +++++--
arch/arm64/include/asm/thread_info.h | 3 +++
arch/arm64/kernel/process.c | 8 ++++++++
3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 517b9ff0456c..9c4434b8a9a8 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -137,9 +137,13 @@ typedef struct user_fpsimd_state elf_fpregset_t;
*/
#define ELF_PLAT_INIT(_r, load_addr) (_r)->regs[0] = 0
+/*
+ * Don't modify this macro unless you add new personality.
+ * All personality-related setup should be done at proper place.
+ * If not sure, consider the arch_setup_new_exec() function.
+ */
#define SET_PERSONALITY(ex) \
({ \
- current->mm->context.flags = 0; \
clear_thread_flag(TIF_32BIT); \
current->personality &= ~READ_IMPLIES_EXEC; \
})
@@ -195,7 +199,6 @@ typedef compat_elf_greg_t compat_elf_gregset_t[COMPAT_ELF_NGREG];
*/
#define COMPAT_SET_PERSONALITY(ex) \
({ \
- current->mm->context.flags = MMCF_AARCH32; \
set_thread_flag(TIF_32BIT); \
})
#define COMPAT_ARCH_DLINFO
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 46c3b93cf865..c823d2f12b4c 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -68,6 +68,9 @@ struct thread_info {
#define thread_saved_fp(tsk) \
((unsigned long)(tsk->thread.cpu_context.fp))
+void arch_setup_new_exec(void);
+#define arch_setup_new_exec arch_setup_new_exec
+
#endif
/*
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 659ae8094ed5..e99012c4803a 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -417,3 +417,11 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
else
return randomize_page(mm->brk, SZ_1G);
}
+
+/*
+ * Called immediately after a successful exec.
+ */
+void arch_setup_new_exec(void)
+{
+ current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
+}
--
2.11.0
On Sun, Aug 20, 2017 at 01:20:46PM +0300, Yury Norov wrote:
> This patchset is the result of discussion:
> https://lkml.org/lkml/2017/7/31/454
>
> First patch introduces MMCF flags for mm_context_t ->flags to separate it from
> TIF ones. And second patch moves personality-related setup code from
> SET_PERSONALITY() to the helper.
>
> Yury Norov (2):
> arm64: introduce separated bits for mm_context_t flags
> arm64: cleanup {COMPAT_,}SET_PERSONALITY() macro
Patches queued for 4.14. Thanks.
--
Catalin