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.akashi@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.
Will