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.
CC: Catalin Marinas <[email protected]>
CC: Pratyush Anand <[email protected]>
Yury Norov (2):
arm64: introduce separated bits for mm_context_t flags
arm64: cleanup {COMPAT_,}SET_PERSONALITY() macro
arch/arm64/include/asm/elf.h | 15 +++++++++------
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 | 17 +++++++++++++++++
5 files changed, 32 insertions(+), 7 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.
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 <[email protected]>
CC: Pratyush Anand <[email protected]>
CC: Catalin Marinas <[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 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..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
Originally {COMPAT_,}SET_PERSONALITY() only sets the 32-bit flag in thread_info
structure. But 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
Note: mm->context.flags doesn't require the atomic strong ordered acceess to the
field, so use __set_bit() there;
Signed-off-by: Yury Norov <[email protected]>
CC: Pratyush Anand <[email protected]>
CC: Catalin Marinas <[email protected]>
---
arch/arm64/include/asm/elf.h | 15 +++++++++------
arch/arm64/include/asm/thread_info.h | 3 +++
arch/arm64/kernel/process.c | 17 +++++++++++++++++
3 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index de11ed1484e3..615953243961 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -137,11 +137,14 @@ 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) \
({ \
- clear_bit(MMCF_AARCH32, ¤t->mm->context.flags); \
clear_thread_flag(TIF_32BIT); \
- current->personality &= ~READ_IMPLIES_EXEC; \
})
/* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */
@@ -188,14 +191,14 @@ typedef compat_elf_greg_t compat_elf_gregset_t[COMPAT_ELF_NGREG];
((x)->e_flags & EF_ARM_EABI_MASK))
#define compat_start_thread compat_start_thread
+
/*
- * Unlike the native SET_PERSONALITY macro, the compat version inherits
- * READ_IMPLIES_EXEC across a fork() since this is the behaviour on
- * arch/arm/.
+ * 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 COMPAT_SET_PERSONALITY(ex) \
({ \
- set_bit(MMCF_AARCH32, ¤t->mm->context.flags); \
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..ebca9e4f62c7 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -417,3 +417,20 @@ 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 = 0;
+
+ /*
+ * Unlike the native one, the compat version of exec() inherits
+ * READ_IMPLIES_EXEC since this is the behaviour on arch/arm/.
+ */
+ if (is_compat_task())
+ __set_bit(MMCF_AARCH32, ¤t->mm->context.flags);
+ else
+ current->personality &= ~READ_IMPLIES_EXEC;
+}
--
2.11.0
On Sat, Aug 05, 2017 at 05:40:21PM +0300, Yury Norov wrote:
> 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 */
Nitpick: drop 0x since it's a bit number not a flag value. We could,
however, make it a value and just stop using (set|clear)_bit functions.
There is no atomicity issue here.
--
Catalin
On Sat, Aug 05, 2017 at 05:40:22PM +0300, Yury Norov wrote:
> Originally {COMPAT_,}SET_PERSONALITY() only sets the 32-bit flag in thread_info
> structure. But 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
>
> Note: mm->context.flags doesn't require the atomic strong ordered acceess to the
> field, so use __set_bit() there;
As I replied to patch 1, we don't even need __set_bit() but just '|='
for setting and '&' for testing.
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index de11ed1484e3..615953243961 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -137,11 +137,14 @@ 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) \
> ({ \
> - clear_bit(MMCF_AARCH32, ¤t->mm->context.flags); \
> clear_thread_flag(TIF_32BIT); \
> - current->personality &= ~READ_IMPLIES_EXEC; \
> })
What I meant is that we keep the personality setting in SET_PERSONALITY,
together with the existing TIF bits but just move the mm->context.flags
setting out.
> 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
I'm fine with out of line implementation, it probably helps with any
header conflicts (and it's not a fast path anyway).
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 659ae8094ed5..ebca9e4f62c7 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -417,3 +417,20 @@ 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 = 0;
> +
> + /*
> + * Unlike the native one, the compat version of exec() inherits
> + * READ_IMPLIES_EXEC since this is the behaviour on arch/arm/.
> + */
> + if (is_compat_task())
> + __set_bit(MMCF_AARCH32, ¤t->mm->context.flags);
> + else
> + current->personality &= ~READ_IMPLIES_EXEC;
> +}
As I said above, just context.flags |= MMCF_AARCH32.
Thanks.
--
Catalin