On 11/27/2014 11:10 PM, Will Deacon wrote:
On Thu, Nov 27, 2014 at 05:53:36AM +0000, AKASHI Takahiro wrote:
On 11/26/2014 09:41 PM, Will Deacon wrote:
On Wed, Nov 26, 2014 at 04:49:46AM +0000, AKASHI Takahiro wrote:
This regeset is intended to be used to get and set a system call number
while tracing.
There was some discussion about possible approaches to do so:
(1) modify x8 register with ptrace(PTRACE_SETREGSET) indirectly,
and update regs->syscallno later on in syscall_trace_enter(), or
(2) define a dedicated regset for this purpose as on s390, or
(3) support ptrace(PTRACE_SET_SYSCALL) as on arch/arm
Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to
tracer as well as that secure_computing() expects a changed syscall number,
especially case of -1, to be visible before this function returns in
syscall_trace_enter(), (1) doesn't work well.
We will take (2) since it looks much cleaner.
Signed-off-by: AKASHI Takahiro <takahiro.aka...@linaro.org>
---
arch/arm64/kernel/ptrace.c | 35 +++++++++++++++++++++++++++++++++++
include/uapi/linux/elf.h | 1 +
2 files changed, 36 insertions(+)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 8a4ae8e..8b98781 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -551,6 +551,32 @@ static int tls_set(struct task_struct *target, const
struct user_regset *regset,
return ret;
}
+static int system_call_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ void *kbuf, void __user *ubuf)
+{
+ struct pt_regs *regs = task_pt_regs(target);
+
+ return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+ ®s->syscallno, 0, -1);
Does this work for big-endian machines? regs->syscallno is a u64, but the
regset defines it as an int. I think you need to copy to a temporary
register first.
Right. I will fix it.
Do you prefer to use s32, instead of int, like other regsets?
I don't have a preference either way.
It would be great to have a new revision of these patches ASAP if you're
targetting 3.19.
Yeah, definitely.
-Takahiro AKASHI
Will
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