[PATCH v6 01/19] arm64:ilp32: add documentation on the ILP32 ABI for ARM64

Yury Norov
2015-11-17T21:16:41Z

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.

Reviewed-by: David Daney <ddaney@caviumnetworks.com>

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>
---
Documentation/arm64/ilp32.txt | 47 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 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..93c09f2
--- /dev/null
+++ b/Documentation/arm64/ilp32.txt
@@ -0,0 +1,47 @@
+ILP32 AARCH64 SYSCALL ABI
+=========================
+Written by Andrew Pinski <apinski@cavium.com>
+Updated by Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
+Updated by Yury Norov <ynorov@caviumnetworks.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 LP64 syscalls reused by ILP32 clients, and syscalls having
+ILP32-specific handlers is in arch/arm64/kernel/sys_ilp32.c
+
--
2.1.4