Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-25 Thread Russell King - ARM Linux
On Thu, Nov 20, 2014 at 02:13:04PM +0900, AKASHI Takahiro wrote: > On 11/20/2014 04:06 AM, Will Deacon wrote: > >What does x86 do? > > On x86, syscall(-1) returns -ENOSYS if not traced, and we can change a return > value if traced. ... which is used for UML (user mode Linux). UML works by spawni

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-25 Thread Will Deacon
On Thu, Nov 20, 2014 at 05:52:34AM +, AKASHI Takahiro wrote: > On 11/20/2014 02:13 PM, AKASHI Takahiro wrote: > > On 11/20/2014 04:06 AM, Will Deacon wrote: > >> Ok, but now userspace sees -ENOSYS for a skipped system call in that case, > >> whereas it would usually see whatever the trace put i

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-25 Thread Will Deacon
On Tue, Nov 25, 2014 at 07:42:10AM +, AKASHI Takahiro wrote: > On 11/21/2014 04:17 AM, Will Deacon wrote: > > On Thu, Nov 20, 2014 at 05:13:04AM +, AKASHI Takahiro wrote: > >> On 11/20/2014 04:06 AM, Will Deacon wrote: > >>> On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: >

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-24 Thread AKASHI Takahiro
On 11/21/2014 04:17 AM, Will Deacon wrote: On Thu, Nov 20, 2014 at 05:13:04AM +, AKASHI Takahiro wrote: On 11/20/2014 04:06 AM, Will Deacon wrote: On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: Syscall(-1) will return -ENOSYS whether or not a syscallno is explicitly repla

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-20 Thread Will Deacon
On Thu, Nov 20, 2014 at 05:13:04AM +, AKASHI Takahiro wrote: > On 11/20/2014 04:06 AM, Will Deacon wrote: > > On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: > >> Syscall(-1) will return -ENOSYS whether or not a syscallno is explicitly > >> replaced with -1 by a tracer, and, in

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-19 Thread AKASHI Takahiro
On 11/20/2014 02:13 PM, AKASHI Takahiro wrote: On 11/20/2014 04:06 AM, Will Deacon wrote: On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: On 11/18/2014 11:04 PM, Will Deacon wrote: On Tue, Nov 18, 2014 at 01:10:34AM +, AKASHI Takahiro wrote: +if (((int)regs->syscalln

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-19 Thread AKASHI Takahiro
On 11/20/2014 04:06 AM, Will Deacon wrote: On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: On 11/18/2014 11:04 PM, Will Deacon wrote: On Tue, Nov 18, 2014 at 01:10:34AM +, AKASHI Takahiro wrote: + if (((int)regs->syscallno == -1) && (orig_syscallno == -1)) { +

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-19 Thread Will Deacon
On Wed, Nov 19, 2014 at 08:46:19AM +, AKASHI Takahiro wrote: > On 11/18/2014 11:04 PM, Will Deacon wrote: > > On Tue, Nov 18, 2014 at 01:10:34AM +, AKASHI Takahiro wrote: > >> > >> + if (((int)regs->syscallno == -1) && (orig_syscallno == -1)) { > >> + /* > >> + * user-is

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-19 Thread AKASHI Takahiro
On 11/18/2014 11:04 PM, Will Deacon wrote: On Tue, Nov 18, 2014 at 01:10:34AM +, AKASHI Takahiro wrote: + if (((int)regs->syscallno == -1) && (orig_syscallno == -1)) { + /* +* user-issued syscall(-1): +* RESTRICTION: We always return ENOSY

Re: [PATCH v8 2/6] arm64: ptrace: allow tracer to skip a system call

2014-11-18 Thread Will Deacon
On Tue, Nov 18, 2014 at 01:10:34AM +, AKASHI Takahiro wrote: > If tracer specifies -1 as a syscall number, this traced system call should > be skipped with a return value specified in x0. > This patch implements this semantics, but there is one restriction here: > > syscall(-1) always retu