[PATCH v3 1/2] powerpc/ptrace: simplify gpr_get/tm_cgpr_get
Christophe Leroy
christophe.leroy at csgroup.eu
Fri Nov 20 04:16:16 AEDT 2020
Le 19/11/2020 à 17:02, Oleg Nesterov a écrit :
> gpr_get() does membuf_write() twice to override pt_regs->msr in between.
Is there anything wrong with that ?
> We can call membuf_write() once and change ->msr in the kernel buffer,
> this simplifies the code and the next fix.
>
> The patch adds a new simple helper, membuf_at(offs), it returns the new
> membuf which can be safely used after membuf_write().
>
> Signed-off-by: Oleg Nesterov <oleg at redhat.com>
> ---
> arch/powerpc/kernel/ptrace/ptrace-tm.c | 13 +++++--------
> arch/powerpc/kernel/ptrace/ptrace-view.c | 13 +++++--------
> include/linux/regset.h | 12 ++++++++++++
> 3 files changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/kernel/ptrace/ptrace-tm.c b/arch/powerpc/kernel/ptrace/ptrace-tm.c
> index 54f2d076206f..f8fcbd85d4cb 100644
> --- a/arch/powerpc/kernel/ptrace/ptrace-tm.c
> +++ b/arch/powerpc/kernel/ptrace/ptrace-tm.c
> @@ -86,6 +86,8 @@ int tm_cgpr_active(struct task_struct *target, const struct user_regset *regset)
> int tm_cgpr_get(struct task_struct *target, const struct user_regset *regset,
> struct membuf to)
> {
> + struct membuf to_msr = membuf_at(&to, offsetof(struct pt_regs, msr));
> +
> if (!cpu_has_feature(CPU_FTR_TM))
> return -ENODEV;
>
> @@ -97,17 +99,12 @@ int tm_cgpr_get(struct task_struct *target, const struct user_regset *regset,
> flush_altivec_to_thread(target);
>
> membuf_write(&to, &target->thread.ckpt_regs,
> - offsetof(struct pt_regs, msr));
> - membuf_store(&to, get_user_ckpt_msr(target));
> + sizeof(struct user_pt_regs));
This looks mis-aligned. But it should fit on a single line, now we allow up to 100 chars on a line.
>
> - BUILD_BUG_ON(offsetof(struct pt_regs, orig_gpr3) !=
> - offsetof(struct pt_regs, msr) + sizeof(long));
> + membuf_store(&to_msr, get_user_ckpt_msr(target));
>
> - membuf_write(&to, &target->thread.ckpt_regs.orig_gpr3,
> - sizeof(struct user_pt_regs) -
> - offsetof(struct pt_regs, orig_gpr3));
> return membuf_zero(&to, ELF_NGREG * sizeof(unsigned long) -
> - sizeof(struct user_pt_regs));
> + sizeof(struct user_pt_regs));
I can't see any change here except the alignment. Can you leave it as is ?
> }
>
> /*
> diff --git a/arch/powerpc/kernel/ptrace/ptrace-view.c b/arch/powerpc/kernel/ptrace/ptrace-view.c
> index 7e6478e7ed07..39686ede40b3 100644
> --- a/arch/powerpc/kernel/ptrace/ptrace-view.c
> +++ b/arch/powerpc/kernel/ptrace/ptrace-view.c
> @@ -217,6 +217,7 @@ int ptrace_put_reg(struct task_struct *task, int regno, unsigned long data)
> static int gpr_get(struct task_struct *target, const struct user_regset *regset,
> struct membuf to)
> {
> + struct membuf to_msr = membuf_at(&to, offsetof(struct pt_regs, msr));
> int i;
>
> if (target->thread.regs == NULL)
> @@ -228,17 +229,13 @@ static int gpr_get(struct task_struct *target, const struct user_regset *regset,
> target->thread.regs->gpr[i] = NV_REG_POISON;
> }
>
> - membuf_write(&to, target->thread.regs, offsetof(struct pt_regs, msr));
> - membuf_store(&to, get_user_msr(target));
> + membuf_write(&to, target->thread.regs,
> + sizeof(struct user_pt_regs));
This should fit on a single line.
>
> - BUILD_BUG_ON(offsetof(struct pt_regs, orig_gpr3) !=
> - offsetof(struct pt_regs, msr) + sizeof(long));
> + membuf_store(&to_msr, get_user_msr(target));
>
> - membuf_write(&to, &target->thread.regs->orig_gpr3,
> - sizeof(struct user_pt_regs) -
> - offsetof(struct pt_regs, orig_gpr3));
> return membuf_zero(&to, ELF_NGREG * sizeof(unsigned long) -
> - sizeof(struct user_pt_regs));
> + sizeof(struct user_pt_regs));
This should not change, it's not part of the changes for this patch.
> }
>
> static int gpr_set(struct task_struct *target, const struct user_regset *regset,
> diff --git a/include/linux/regset.h b/include/linux/regset.h
> index c3403f328257..a00765f0e8cf 100644
> --- a/include/linux/regset.h
> +++ b/include/linux/regset.h
> @@ -46,6 +46,18 @@ static inline int membuf_write(struct membuf *s, const void *v, size_t size)
> return s->left;
> }
>
> +static inline struct membuf membuf_at(const struct membuf *s, size_t offs)
> +{
> + struct membuf n = *s;
Is there any point in using a struct membuf * instaed of a struct membuf as parameter ?
> +
> + if (offs > n.left)
> + offs = n.left;
> + n.p += offs;
> + n.left -= offs;
> +
> + return n;
> +}
> +
> /* current s->p must be aligned for v; v must be a scalar */
> #define membuf_store(s, v) \
> ({ \
>
Christophe
More information about the Linuxppc-dev
mailing list