[PATCH 2/2] selftests/seccomp: add sparc64 support

[Stian Halseth <stian@itx.no>]

sparc64 now selects HAVE_ARCH_SECCOMP_FILTER, so teach seccomp_bpf
how to read and write its registers: the syscall number lives in %g1
and the return value in %o0, addressed through the NT_PRSTATUS regset
(16 u_regs, 16 window registers, then tstate/tpc/tnpc/y).

Errors are signaled by the carry bit in tstate with a positive errno
value in %o0, so provide a SYSCALL_RET_SET that maintains both, and
mark the arch SYSCALL_RET_SET_ON_PTRACE_EXIT since a return value
poked at entry would be overwritten by the syscall skip path, as on
powerpc.

Passes 95 of 95 on an UltraSPARC T4-1 (16 skipped for missing
optional features such as uprobes).

Link: https://github.com/sparclinux/issues/issues/11
Signed-off-by: Stian Halseth <stian@itx.no>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 0622bc2acad4..30b777f357d8 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -1872,6 +1872,41 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 # define ARCH_REGS		struct user_regs_struct
 # define SYSCALL_NUM(_regs)	(_regs).orig_d0
 # define SYSCALL_RET(_regs)	(_regs).d0
+#elif defined(__sparc__) && defined(__arch64__)
+/*
+ * The NT_PRSTATUS regset: %g0-%g7 and %o0-%o7, the 16 window
+ * registers as read back from the stack, then tstate, tpc, tnpc
+ * and y.
+ */
+struct sparc64_user_regs {
+	__u64 u_regs[16];
+	__u64 window[16];
+	__u64 tstate;
+	__u64 tpc;
+	__u64 tnpc;
+	__u64 y;
+};
+# define ARCH_REGS		struct sparc64_user_regs
+# define SYSCALL_NUM(_regs)	(_regs).u_regs[1]	/* %g1 */
+# define SYSCALL_RET(_regs)	(_regs).u_regs[8]	/* %o0 */
+/*
+ * A syscall error is signaled by the carry bit in tstate, with the
+ * errno held in %o0 as a positive value; the carry can only be
+ * written reliably once the syscall has been skipped or has run.
+ */
+# define SPARC64_TSTATE_CARRY	0x0000001100000000UL	/* xcc.c | icc.c */
+# define SYSCALL_RET_SET(_regs, _val)				\
+	do {							\
+		typeof(_val) _result = (_val);			\
+		if (_result < 0) {				\
+			SYSCALL_RET(_regs) = -_result;		\
+			(_regs).tstate |= SPARC64_TSTATE_CARRY;	\
+		} else {					\
+			SYSCALL_RET(_regs) = _result;		\
+			(_regs).tstate &= ~SPARC64_TSTATE_CARRY; \
+		}						\
+	} while (0)
+# define SYSCALL_RET_SET_ON_PTRACE_EXIT
 #else
 # error "Do not know how to find your architecture's registers and syscalls"
 #endif
-- 
2.43.0