[B][SRU][PATCH 0/2] Provide ppc64el syscall for pkey_*

[Dan Streetman]

From: Dan Streetman <ddstreet at canonical.com>

BugLink: https://bugs.launchpad.net/bugs/1821625

In bionic, all archs provided by Ubuntu either define __NR_pkey_mprotect
(arm/x86) or define __IGNORE_pkey_mprotect (powerpc/s390).  This value was
used, until libseccomp was updated via bug 1815415, to instead (if
__NR_pkey_mprotect was not defined by the kernel headers) define it as a
negative error value:

+#define __PNR_pkey_mprotect    -10201
+#ifndef __NR_pkey_mprotect
+#define __NR_pkey_mprotect     __PNR_pkey_mprotect
+#endif /* __NR_pkey_mprotect */

systemd, the next time it was built against libseccomp, pulled that
__NR_pkey_mprotect value and started using it for ppc64el, though it was
a negative error value, so it would not actually work as a syscall number.
This caused the systemd test-seccomp autopkgtest to start failing, as
the systemd function it tested only issued the pkey_mprotect syscall if
__NR_pkey_mprotect was defined.

After these patches are applied to bionic, both libseccomp and systemd will
need to be rebuilt - libseccomp rebuilt against the kernel headers, and
systemd against the libseccomp headers.

Note this is not only a fix to allow a test to pass, this actually
provides the syscall number for the functionality on ppc64el on bionic,
which would have failed before (on ppc64el on bionic, but not x86/arm
on bionic); specifically one example is the systemd usage
MemoryDenyWriteExecution as shown in bug 1725348.

Also note that s390x also defines __IGNORE_pkey_mprotect, but the systemd
test only expects its test case to pass for select archs, and s390x is not
one of them, so it has always expected a failure there.  It appears s390x
still does not support pkey_mprotect (it defined pkey_* starting at
commit b41c51c8e194c0bdfb4b1778a137aea8246c86cd, but appears to still
not support them).

Ram Pai (2):
  powerpc: sys_pkey_alloc() and sys_pkey_free() system calls
  powerpc: sys_pkey_mprotect() system call

 arch/powerpc/include/asm/systbl.h      | 3 +++
 arch/powerpc/include/asm/unistd.h      | 6 +-----
 arch/powerpc/include/uapi/asm/unistd.h | 3 +++
 3 files changed, 7 insertions(+), 5 deletions(-)

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2.20.1