[PATCH][RFC] pseudo: intercept syscall() and return ENOTSUP for renameat2

[Ross Burton <ross.burton@intel.com>]

coreutils is now using renameat2() in mv(1) but as this syscall isn't in most
glibc headers yet it falls back to directly calling syscall(), which pseudo
doesn't intercept.  This results in permission problems as files mysteriously
move without pseudo knowing.

This patch intercepts syscall() and returns ENOTSUP if renameat2() is being
called.  Thanks to Andre McCurdy for the proof-of-concept that this patch is
based on.

Signed-off-by: Ross Burton <ross.burton@intel.com>
---
 meta/recipes-devtools/pseudo/files/renameat2.patch | 63 ++++++++++++++++++++++
 meta/recipes-devtools/pseudo/pseudo_git.bb         |  1 +
 2 files changed, 64 insertions(+)
 create mode 100644 meta/recipes-devtools/pseudo/files/renameat2.patch

diff --git a/meta/recipes-devtools/pseudo/files/renameat2.patch b/meta/recipes-devtools/pseudo/files/renameat2.patch
new file mode 100644
index 00000000000..467b0b3e79f
--- /dev/null
+++ b/meta/recipes-devtools/pseudo/files/renameat2.patch
@@ -0,0 +1,63 @@
+commit 3a4c536817dce4d0cbaa8f4efe30e722108357dd
+Author: Ross Burton <ross.burton@intel.com>
+Date:   Tue Mar 27 14:02:10 2018 +0100
+
+    HACK syscall
+
+diff --git a/ports/linux/guts/syscall.c b/ports/linux/guts/syscall.c
+new file mode 100644
+index 0000000..4ed38ed
+--- /dev/null
++++ b/ports/linux/guts/syscall.c
+@@ -0,0 +1,30 @@
++/*
++ * Copyright (c) 2018 Wind River Systems; see
++ * guts/COPYRIGHT for information.
++ *
++ * long syscall(long number, ...)
++ *	long rc = -1;
++ */
++	typedef long syscall_arg_t;
++	syscall_arg_t a,b,c,d,e,f;
++
++	//va_start (ap, number);
++	a = va_arg (ap, syscall_arg_t);
++	b = va_arg (ap, syscall_arg_t);
++	c = va_arg (ap, syscall_arg_t);
++	d = va_arg (ap, syscall_arg_t);
++	e = va_arg (ap, syscall_arg_t);
++	f = va_arg (ap, syscall_arg_t);
++	va_end (ap);
++
++	if ((number == SYS_renameat2)) {
++			errno = ENOTSUP;
++			rc = -1;
++	}
++	else {
++			rc = real_syscall (number, a, b, c, d, e, f);
++	}
++
++/*	return rc;
++ * }
++ */
+diff --git a/ports/linux/wrapfuncs.in b/ports/linux/wrapfuncs.in
+index fca5b50..137612c 100644
+--- a/ports/linux/wrapfuncs.in
++++ b/ports/linux/wrapfuncs.in
+@@ -54,3 +54,4 @@ int getpw(uid_t uid, char *buf);
+ int getpwent_r(struct passwd *pwbuf, char *buf, size_t buflen, struct passwd **pwbufp);
+ int getgrent_r(struct group *gbuf, char *buf, size_t buflen, struct group **gbufp);
+ int capset(cap_user_header_t hdrp, const cap_user_data_t datap); /* real_func=pseudo_capset */
++long syscall(long number, ...);
+diff --git a/pseudo_wrappers.c b/pseudo_wrappers.c
+index e05f73a..b7225d7 100644
+--- a/pseudo_wrappers.c
++++ b/pseudo_wrappers.c
+@@ -36,6 +36,7 @@
+ #include <sys/time.h>
+ #include <sys/wait.h>
+ #include <dlfcn.h>
++#include <sys/syscall.h>
+ 
+ /* include this to get PSEUDO_PORT_* definitions */
+ #include "pseudo.h"
diff --git a/meta/recipes-devtools/pseudo/pseudo_git.bb b/meta/recipes-devtools/pseudo/pseudo_git.bb
index 66da1cc53b8..44343c3bc57 100644
--- a/meta/recipes-devtools/pseudo/pseudo_git.bb
+++ b/meta/recipes-devtools/pseudo/pseudo_git.bb
@@ -6,6 +6,7 @@ SRC_URI = "git://git.yoctoproject.org/pseudo \
            file://fallback-group \
            file://moreretries.patch \
            file://toomanyfiles.patch \
+           file://renameat2.patch \
            "
 
 SRCREV = "d7c31a25e4b02af0c64e6be0b4b0a9ac4ffc9da2"
-- 
2.11.0