Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail
On 11.02.2015 05:04, Michael Ellerman wrote: On Mon, 2015-02-09 at 07:55 +, Bogdan Purcareata wrote: In certain scenarios - e.g. seccomp filtering with ERRNO as default action - the system call fails for other reasons than the syscall not being available. The seccomp filter can be configured to store a user-defined error code on return from a blacklisted syscall. The RFC is this: are there currently any user-space scenarios where it is required that the system call return ENOSYS as error code on failure, no matter the circumstances? I don't want to break userspace requirements. I have not added code to force this error code in situations different than secure_computing failure, in order to keep overhead at a minimum. Signed-off-by: Bogdan Purcareata --- arch/powerpc/kernel/entry_32.S | 3 ++- arch/powerpc/kernel/entry_64.S | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 59848e5..52e48dd 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX) b 1b #endif /* CONFIG_44x */ -66:li r3,-ENOSYS +66: +# li r3,-ENOSYS b ret_from_syscall .globl ret_from_fork diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e6bfe8e..80db02e 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -269,7 +269,7 @@ syscall_dotrace: b .Lsyscall_dotrace_cont syscall_enosys: - li r3,-ENOSYS +# li r3,-ENOSYS b syscall_exit So what happens if you call this with a syscall number that's out of bounds? As far as my current understanding goes, the call will return with -1 with a errno that's undefined (or I've not seen it be defined anywhere). I've thought more about this, and I guess the best option would be to move setting -ENOSYS as errno from the syscall entry assembly to do_syscall_trace_enter (as opposed to eliminating it at all). I was a little reluctant to do this at first in order to keep overhead to a minimum, but it's certainly not an option to change behavior if the syscall number is out of bounds. v2 to come shortly. Thanks, Bogdan P. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail
On Mon, 2015-02-09 at 07:55 +, Bogdan Purcareata wrote: > In certain scenarios - e.g. seccomp filtering with ERRNO as default action - > the system call fails for other reasons than the syscall not being available. > The seccomp filter can be configured to store a user-defined error code on > return from a blacklisted syscall. > > The RFC is this: are there currently any user-space scenarios where it is > required that the system call return ENOSYS as error code on failure, no > matter > the circumstances? I don't want to break userspace requirements. I have not > added code to force this error code in situations different than > secure_computing failure, in order to keep overhead at a minimum. > > Signed-off-by: Bogdan Purcareata > --- > arch/powerpc/kernel/entry_32.S | 3 ++- > arch/powerpc/kernel/entry_64.S | 2 +- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S > index 59848e5..52e48dd 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX) > b 1b > #endif /* CONFIG_44x */ > > -66: li r3,-ENOSYS > +66: > +#li r3,-ENOSYS > b ret_from_syscall > > .globl ret_from_fork > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > index e6bfe8e..80db02e 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -269,7 +269,7 @@ syscall_dotrace: > b .Lsyscall_dotrace_cont > > syscall_enosys: > - li r3,-ENOSYS > +#li r3,-ENOSYS > b syscall_exit So what happens if you call this with a syscall number that's out of bounds? cheers ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail
Obvious mistake on my behalf to send the patch with lines commented out. I will fix it in v2. On 09.02.2015 09:55, Bogdan Purcareata wrote: In certain scenarios - e.g. seccomp filtering with ERRNO as default action - the system call fails for other reasons than the syscall not being available. The seccomp filter can be configured to store a user-defined error code on return from a blacklisted syscall. The RFC is this: are there currently any user-space scenarios where it is required that the system call return ENOSYS as error code on failure, no matter the circumstances? I don't want to break userspace requirements. I have not added code to force this error code in situations different than secure_computing failure, in order to keep overhead at a minimum. Signed-off-by: Bogdan Purcareata --- arch/powerpc/kernel/entry_32.S | 3 ++- arch/powerpc/kernel/entry_64.S | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 59848e5..52e48dd 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX) b 1b #endif /* CONFIG_44x */ -66:li r3,-ENOSYS +66: +# li r3,-ENOSYS b ret_from_syscall .globl ret_from_fork diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e6bfe8e..80db02e 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -269,7 +269,7 @@ syscall_dotrace: b .Lsyscall_dotrace_cont syscall_enosys: - li r3,-ENOSYS +# li r3,-ENOSYS b syscall_exit syscall_exit_work: ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail
In certain scenarios - e.g. seccomp filtering with ERRNO as default action - the system call fails for other reasons than the syscall not being available. The seccomp filter can be configured to store a user-defined error code on return from a blacklisted syscall. The RFC is this: are there currently any user-space scenarios where it is required that the system call return ENOSYS as error code on failure, no matter the circumstances? I don't want to break userspace requirements. I have not added code to force this error code in situations different than secure_computing failure, in order to keep overhead at a minimum. Signed-off-by: Bogdan Purcareata --- arch/powerpc/kernel/entry_32.S | 3 ++- arch/powerpc/kernel/entry_64.S | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 59848e5..52e48dd 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX) b 1b #endif /* CONFIG_44x */ -66:li r3,-ENOSYS +66: +# li r3,-ENOSYS b ret_from_syscall .globl ret_from_fork diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e6bfe8e..80db02e 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -269,7 +269,7 @@ syscall_dotrace: b .Lsyscall_dotrace_cont syscall_enosys: - li r3,-ENOSYS +# li r3,-ENOSYS b syscall_exit syscall_exit_work: -- 2.1.4 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
