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powerpc/ptrace: Simplify gpr_get()/tm_cgpr_get()

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gpr_get() does membuf_write() twice to override pt_regs->msr in
between. 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@redhat.com>
[mpe: Fixup some minor whitespace issues noticed by Christophe]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201119160221.GA5188@redhat.com
This commit is contained in:
Oleg Nesterov 2020-11-19 17:02:21 +01:00 committed by Michael Ellerman
parent 20fa40b147
commit 640586f8af
3 changed files with 19 additions and 15 deletions
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12
arch/powerpc/kernel/ptrace/ptrace-tm.c
View File

@ -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;
@ -96,16 +98,10 @@ int tm_cgpr_get(struct task_struct *target, const struct user_regset *regset,
flush_fp_to_thread(target);
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));
membuf_write(&to, &target->thread.ckpt_regs, sizeof(struct user_pt_regs));
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));
}

10
arch/powerpc/kernel/ptrace/ptrace-view.c
View File

@ -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)
@ -228,15 +229,10 @@ 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));
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));
}

12
include/linux/regset.h
View File

@ -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;
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) \
({ \