ia64: syscall: add some helpful documentation

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

diff --git a/ports/ChangeLog.ia64 b/ports/ChangeLog.ia64
index 34391c1311900b412c9788f165ac4383b34311ca..8e9b24dd4263ffce078e0b797b9b80f97336d65f 100644 (file)
--- a/ports/ChangeLog.ia64
+++ b/ports/ChangeLog.ia64
@@ -1,3 +1,7 @@
+2013-12-29  Mike Frysinger  <vapier@gentoo.org>
+
+       * sysdeps/unix/sysv/linux/ia64/syscall.S: Add a comment.
+
 2013-12-25  Mike Frysinger  <vapier@gentoo.org>
 
        * sysdeps/unix/sysv/linux/ia64/nptl/lowlevellock.h

diff --git a/ports/sysdeps/unix/sysv/linux/ia64/syscall.S b/ports/sysdeps/unix/sysv/linux/ia64/syscall.S
index 8bb77d255cd4753cc083d644ac8fe813f7c302ed..4cd75b8d4c00441d835bfb37db76ecafc3a23c6b 100644 (file)
--- a/ports/sysdeps/unix/sysv/linux/ia64/syscall.S
+++ b/ports/sysdeps/unix/sysv/linux/ia64/syscall.S
@@ -19,6 +19,10 @@
 #include <sysdep.h>
 
 ENTRY(syscall)
+       /* We are called like so:
+          {out0,out1,...,out6} registers -> {NR, arg1, ..., arg6}
+          Shift the register window so that {out1...out6} are available
+          in {out0...out5} like the kernel syscall handler expects.  */
        alloc r2=ar.pfs,1,0,8,0
        mov r15=r32             /* syscall number */
        break __BREAK_SYSCALL