Commit 640586f8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Michael Ellerman
Browse files

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



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: default avatarOleg Nesterov <oleg@redhat.com>
[mpe: Fixup some minor whitespace issues noticed by Christophe]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201119160221.GA5188@redhat.com
parent 20fa40b1

arch/powerpc/kernel/ptrace/ptrace-tm.c

+4 −8
Original line number Diff line number Diff line
@@ -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));

}

arch/powerpc/kernel/ptrace/ptrace-view.c

+3 −7
Original line number Diff line number Diff line
@@ -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));

}

include/linux/regset.h

+12 −0
Original line number Diff line number Diff line
@@ -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)				\

({							\

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