powerpc: Split user/kernel definitions of struct pt_regs

mpe · mpe · commit 002af9391bfb · 2018-10-14T18:04:09.000+11:00
We use a shared definition for struct pt_regs in uapi/asm/ptrace.h.
That means the layout of the structure is ABI, ie. we can't change it.

That would be fine if it was only used to describe the user-visible
register state of a process, but it's also the struct we use in the
kernel to describe the registers saved in an interrupt frame.

We'd like more flexibility in the content (and possibly layout) of the
kernel version of the struct, but currently that's not possible.

So split the definition into a user-visible definition which remains
unchanged, and a kernel internal one.

At the moment they're still identical, and we check that at build
time. That's because we have code (in ptrace etc.) that assumes that
they are the same. We will fix that code in future patches, and then
we can break the strict symmetry between the two structs.

Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
@@ -26,6 +26,33 @@
 #include <uapi/asm/ptrace.h>
 #include <asm/asm-const.h>
 
+#ifndef __ASSEMBLY__
+struct pt_regs
+{
+	union {
+		struct user_pt_regs user_regs;
+		struct {
+			unsigned long gpr[32];
+			unsigned long nip;
+			unsigned long msr;
+			unsigned long orig_gpr3;
+			unsigned long ctr;
+			unsigned long link;
+			unsigned long xer;
+			unsigned long ccr;
+#ifdef CONFIG_PPC64
+			unsigned long softe;
+#else
+			unsigned long mq;
+#endif
+			unsigned long trap;
+			unsigned long dar;
+			unsigned long dsisr;
+			unsigned long result;
+		};
+	};
+};
+#endif
 
 #ifdef __powerpc64__
 
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -29,7 +29,12 @@
 
 #ifndef __ASSEMBLY__
 
-struct pt_regs {
+#ifdef __KERNEL__
+struct user_pt_regs
+#else
+struct pt_regs
+#endif
+{
 	unsigned long gpr[32];
 	unsigned long nip;
 	unsigned long msr;
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
@@ -3335,3 +3335,42 @@ void do_syscall_trace_leave(struct pt_regs *regs)
 
 	user_enter();
 }
+
+void __init pt_regs_check(void)
+{
+	BUILD_BUG_ON(offsetof(struct pt_regs, gpr) !=
+		     offsetof(struct user_pt_regs, gpr));
+	BUILD_BUG_ON(offsetof(struct pt_regs, nip) !=
+		     offsetof(struct user_pt_regs, nip));
+	BUILD_BUG_ON(offsetof(struct pt_regs, msr) !=
+		     offsetof(struct user_pt_regs, msr));
+	BUILD_BUG_ON(offsetof(struct pt_regs, msr) !=
+		     offsetof(struct user_pt_regs, msr));
+	BUILD_BUG_ON(offsetof(struct pt_regs, orig_gpr3) !=
+		     offsetof(struct user_pt_regs, orig_gpr3));
+	BUILD_BUG_ON(offsetof(struct pt_regs, ctr) !=
+		     offsetof(struct user_pt_regs, ctr));
+	BUILD_BUG_ON(offsetof(struct pt_regs, link) !=
+		     offsetof(struct user_pt_regs, link));
+	BUILD_BUG_ON(offsetof(struct pt_regs, xer) !=
+		     offsetof(struct user_pt_regs, xer));
+	BUILD_BUG_ON(offsetof(struct pt_regs, ccr) !=
+		     offsetof(struct user_pt_regs, ccr));
+#ifdef __powerpc64__
+	BUILD_BUG_ON(offsetof(struct pt_regs, softe) !=
+		     offsetof(struct user_pt_regs, softe));
+#else
+	BUILD_BUG_ON(offsetof(struct pt_regs, mq) !=
+		     offsetof(struct user_pt_regs, mq));
+#endif
+	BUILD_BUG_ON(offsetof(struct pt_regs, trap) !=
+		     offsetof(struct user_pt_regs, trap));
+	BUILD_BUG_ON(offsetof(struct pt_regs, dar) !=
+		     offsetof(struct user_pt_regs, dar));
+	BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) !=
+		     offsetof(struct user_pt_regs, dsisr));
+	BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
+		     offsetof(struct user_pt_regs, result));
+
+	BUILD_BUG_ON(sizeof(struct user_pt_regs) > sizeof(struct pt_regs));
+}
