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 <o...@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
