BACKPORT: arm64: add SIGSYS siginfo for compat task

SIGSYS is primarily used in secure computing to notify tracer of syscall
events. This patch allows signal handler on compat task to get correct
information with SA_SIGINFO specified when this signal is delivered.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

Bug: 28020023
Patchset: seccomp

(cherry picked from kernel/msm commit 369529f9c3401b6172c8c784fae089c7752d613e)
Signed-off-by: Kees Cook <keescook@google.com>
Change-Id: I0eed2aee35bc4fe22170c53528b95d6d163156b2
diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
index 253e33b..5b01f92 100644
--- a/arch/arm64/include/asm/compat.h
+++ b/arch/arm64/include/asm/compat.h
@@ -205,6 +205,13 @@
 			compat_long_t _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
 			int _fd;
 		} _sigpoll;
+
+		/* SIGSYS */
+		struct {
+			compat_uptr_t _call_addr; /* calling user insn */
+			int _syscall;	/* triggering system call number */
+			compat_uint_t _arch;	/* AUDIT_ARCH_* of syscall */
+		} _sigsys;
 	} _sifields;
 } compat_siginfo_t;
 
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index c5ee208..e8a17da 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -186,6 +186,12 @@
 		err |= __put_user(from->si_uid, &to->si_uid);
 		err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, &to->si_ptr);
 		break;
+	case __SI_SYS:
+		err |= __put_user((compat_uptr_t)(unsigned long)
+				from->si_call_addr, &to->si_call_addr);
+		err |= __put_user(from->si_syscall, &to->si_syscall);
+		err |= __put_user(from->si_arch, &to->si_arch);
+		break;
 	default: /* this is just in case for now ... */
 		err |= __put_user(from->si_pid, &to->si_pid);
 		err |= __put_user(from->si_uid, &to->si_uid);