[PATCH v6 01/17] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

[PATCH v6 01/17] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

[Yury Norov]

From: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

Based on Andrew Pinski's original patch-series and adapted with changes
to reduce the duplication of code-paths and resolve issue found during
LTP testing.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Andrew Pinski <Andrew.Pinski@caviumnetworks.com>
Reviewed-by: David Daney <david.daney@cavium.com>
---
 Documentation/arm64/ilp32.txt | 55 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Documentation/arm64/ilp32.txt

diff --git a/Documentation/arm64/ilp32.txt b/Documentation/arm64/ilp32.txt
new file mode 100644
index 0000000..4f6860b
--- /dev/null
+++ b/Documentation/arm64/ilp32.txt
@@ -0,0 +1,55 @@
+ILP32 AARCH64 SYSCALL ABI
+=========================
+Written by Andrew Pinski <apinski@cavium.com>
+Updated by Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
+
+
+This document describes the ILP32 syscall ABI and where it differs
+from the generic linux syscall interface.
+
+Some structures are changed to reduce the difference in the code path
+for both ILP32 and LP64 ABIs for signal handling.
+
+The following structures have been changed so the layout of the
+structures are the same between ILP32 and LP64 ABIs, including:
+ * sigval_t        contains pointers
+ * sigevent        Uses sigval_t which causes it to be the same.  Special
+                   handing is needed for reading; in the mq_notify syscall
+ * sigaction       Conversion is handled in the userland (glibc), as the
+		    userland data structures are defined in glibc anyway.
+
+A number of structures differ between ILP32 and LP64, including:
+ * timespec        uses time_t and suseconds_t
+ * timeval         uses time_t and suseconds_t
+ * stat            uses timespec/time_t
+ * semid64_ds      uses time_t.
+ * msqid64_ds      uses time_t.
+ * shmid64_ds      uses time_t.
+ * rt_sigframe     uses siginfo and ucontext.
+ * siginfo_t       uses clock_t and sigval_t
+ * ucontext        uses stack_t and sigset_t
+ * fd_set          This is done to avoid endian issues between ILP32 and
+		   LP64. Syscalls consuming fd_set use timespec.
+ * struct msgbuf   The specification of 'struct msgbuf' defines the 'mtype'
+                   field as a 'long' (i.e. 32bit for ILP32, but 64bit for
+		   LP64).  Functions that operate on 'struct msgbuf' need
+		   to be passed through the compat-syscalls to resolve
+		   this.
+ * stack_t         contains pointers (handled in the compatibility layer)
+
+Also the syscalls which normally would pass 64bit values as two arguments;
+now pass the 64bit value as one argument.  Also they have been renamed
+(removing the 64 from the name) to avoid confusion.
+The list of these LP64 syscalls reused by ILP32 clients is:
+ * fcntl
+ * statfs
+ * fstatfs
+ * truncate
+ * ftruncate
+ * lseek
+ * sendfile
+ * newfstatat
+ * fstat
+ * mmap
+ * fadvise64
+
-- 
2.1.4

Re: [PATCH v6 01/17] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

[Arnd Bergmann]

On Tuesday 03 November 2015 02:30:30 Yury Norov wrote:
> From: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
> 
> Based on Andrew Pinski's original patch-series and adapted with changes
> to reduce the duplication of code-paths and resolve issue found during
> LTP testing.
> 
> Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
> Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
> Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
> Signed-off-by: Andrew Pinski <Andrew.Pinski@caviumnetworks.com>
> Reviewed-by: David Daney <david.daney@cavium.com>

Thanks for the updated version, I'm much happier with this, and only have
some comments on a few details to the later patches.

> +This document describes the ILP32 syscall ABI and where it differs
> +from the generic linux syscall interface.
> +
> +Some structures are changed to reduce the difference in the code path
> +for both ILP32 and LP64 ABIs for signal handling.
> +
> +The following structures have been changed so the layout of the
> +structures are the same between ILP32 and LP64 ABIs, including:
> + * sigval_t        contains pointers
> + * sigevent        Uses sigval_t which causes it to be the same.  Special
> +                   handing is needed for reading; in the mq_notify syscall
> + * sigaction       Conversion is handled in the userland (glibc), as the
> +		    userland data structures are defined in glibc anyway.

Right, makes sense.

> +A number of structures differ between ILP32 and LP64, including:
> + * timespec        uses time_t and suseconds_t
> + * timeval         uses time_t and suseconds_t
> + * stat            uses timespec/time_t

As I commented, we might want to change this for 'stat', which doesn't
really time_t anyway.

> + * semid64_ds      uses time_t.
> + * msqid64_ds      uses time_t.
> + * shmid64_ds      uses time_t.

These use the arm32 layout, right? That's good for consistency.
Fixing these for y2038 will be a bit ugly, but that code can be
shared across all architectures.

> + * rt_sigframe     uses siginfo and ucontext.
> + * siginfo_t       uses clock_t and sigval_t
> + * ucontext        uses stack_t and sigset_t
> + * fd_set          This is done to avoid endian issues between ILP32 and
> +		   LP64. Syscalls consuming fd_set use timespec.
> + * struct msgbuf   The specification of 'struct msgbuf' defines the 'mtype'
> +                   field as a 'long' (i.e. 32bit for ILP32, but 64bit for
> +		   LP64).  Functions that operate on 'struct msgbuf' need
> +		   to be passed through the compat-syscalls to resolve
> +		   this.
> + * stack_t         contains pointers (handled in the compatibility layer)
> +
> +Also the syscalls which normally would pass 64bit values as two arguments;
> +now pass the 64bit value as one argument.  Also they have been renamed
> +(removing the 64 from the name) to avoid confusion.
> +The list of these LP64 syscalls reused by ILP32 clients is:
> + * fcntl
> + * statfs
> + * fstatfs

Did you forget to edit this list? I see fcntl and {f,}statfs use the compat
implementation, not the native one in your patches.

> + * truncate
> + * ftruncate
> + * lseek
> + * sendfile
> + * fadvise64

Makes sense. I think using the normal compat syscalls would have been
just as good here, to save a few lines in the syscall table, but I
agree that the calling conventions are rather silly when you pass
a 64-bit number in two registers.

> + * newfstatat
> + * fstat

This contradicts what you write above regarding separate 'struct stat'.

> + * mmap

Not direct reuse because of the wrapper to check the page size I guess.
Aside from the wrapper, the 32-bit and 64-bit system calls are basically
identical.

	Arnd

Re: [PATCH v6 01/17] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

[Iosif Harutyunov]

Sonicwall is very interested in ILP32, is there a way we can get access to the SuSe builds?

Iosif,_

Re: [PATCH v6 01/17] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

[Yury Norov]

On Wed, Nov 25, 2015 at 03:07:26AM +0000, Iosif Harutyunov wrote:
> Sonicwall is very interested in ILP32, is there a way we can get access to the SuSe builds?
> 
> Iosif,_
> 

Hi Iosif,

I just found your email in trash mailbox. Please add my email to CC
explicitly to avoid it. If you still interested in ILP32, find
RFC6 version here: http://www.spinics.net/lists/linux-s390/msg12272.html

There are also manuals for building glibc for it. I'm not sure
someone was building whole SUSE distro against ILP32, but I think
you can build kernel with my patches, and library, and do tests you
interested. Feel free to contact me in case of troubles.

Yury.

> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/