[PATCH v2 1/4] alpha/uapi: do not expose kernel-only stack frame structures

[Ivan Kokshaysky <ink@unseen.parts>]

Parts of asm/ptrace.h went into UAPI with commit 96433f6ee490
("UAPI: (Scripted) Disintegrate arch/alpha/include/asm") back in 2012.
At first glance it looked correct, as many other architectures expose
'struct pt_regs' for ptrace(2) PTRACE_GETREGS/PTRACE_SETREGS requests
and bpf(2) BPF_PROG_TYPE_KPROBE/BPF_PROG_TYPE_PERF_EVENT program
types.

On Alpha, however, these requests have never been implemented;
'struct pt_regs' describes internal kernel stack frame which has
nothing to do with userspace. Same applies to 'struct switch_stack',
as PTRACE_GETFPREG/PTRACE_SETFPREG are not implemented either.

Move this stuff back into internal asm, where we can ajust it
without causing a lot of confusion about possible UAPI breakage.

Cc: stable@vger.kernel.org
Fixes: 96433f6ee490 ("UAPI: (Scripted) Disintegrate arch/alpha/include/asm")
Signed-off-by: Ivan Kokshaysky <ink@unseen.parts>
---
 arch/alpha/include/asm/ptrace.h      | 62 +++++++++++++++++++++++++-
 arch/alpha/include/uapi/asm/ptrace.h | 65 ++--------------------------
 2 files changed, 64 insertions(+), 63 deletions(-)

diff --git a/arch/alpha/include/asm/ptrace.h b/arch/alpha/include/asm/ptrace.h
index 3557ce64ed21..693d4c5b4dc7 100644
--- a/arch/alpha/include/asm/ptrace.h
+++ b/arch/alpha/include/asm/ptrace.h
@@ -2,8 +2,68 @@
 #ifndef _ASMAXP_PTRACE_H
 #define _ASMAXP_PTRACE_H
 
-#include <uapi/asm/ptrace.h>
+/*
+ * This struct defines the way the registers are stored on the
+ * kernel stack during a system call or other kernel entry
+ *
+ * NOTE! I want to minimize the overhead of system calls, so this
+ * struct has as little information as possible. It does not have
+ *
+ *  - floating point regs: the kernel doesn't change those
+ *  - r9-15: saved by the C compiler
+ *
+ * This makes "fork()" and "exec()" a bit more complex, but should
+ * give us low system call latency.
+ */
 
+struct pt_regs {
+	unsigned long r0;
+	unsigned long r1;
+	unsigned long r2;
+	unsigned long r3;
+	unsigned long r4;
+	unsigned long r5;
+	unsigned long r6;
+	unsigned long r7;
+	unsigned long r8;
+	unsigned long r19;
+	unsigned long r20;
+	unsigned long r21;
+	unsigned long r22;
+	unsigned long r23;
+	unsigned long r24;
+	unsigned long r25;
+	unsigned long r26;
+	unsigned long r27;
+	unsigned long r28;
+	unsigned long hae;
+/* JRP - These are the values provided to a0-a2 by PALcode */
+	unsigned long trap_a0;
+	unsigned long trap_a1;
+	unsigned long trap_a2;
+/* These are saved by PAL-code: */
+	unsigned long ps;
+	unsigned long pc;
+	unsigned long gp;
+	unsigned long r16;
+	unsigned long r17;
+	unsigned long r18;
+};
+
+/*
+ * This is the extended stack used by signal handlers and the context
+ * switcher: it's pushed after the normal "struct pt_regs".
+ */
+struct switch_stack {
+	unsigned long r9;
+	unsigned long r10;
+	unsigned long r11;
+	unsigned long r12;
+	unsigned long r13;
+	unsigned long r14;
+	unsigned long r15;
+	unsigned long r26;
+};
 
 #define arch_has_single_step()		(1)
 #define user_mode(regs) (((regs)->ps & 8) != 0)
diff --git a/arch/alpha/include/uapi/asm/ptrace.h b/arch/alpha/include/uapi/asm/ptrace.h
index 5ca45934fcbb..ad55dc283d8d 100644
--- a/arch/alpha/include/uapi/asm/ptrace.h
+++ b/arch/alpha/include/uapi/asm/ptrace.h
@@ -2,72 +2,13 @@
 #ifndef _UAPI_ASMAXP_PTRACE_H
 #define _UAPI_ASMAXP_PTRACE_H
 
-
 /*
- * This struct defines the way the registers are stored on the
- * kernel stack during a system call or other kernel entry
- *
- * NOTE! I want to minimize the overhead of system calls, so this
- * struct has as little information as possible. It does not have
- *
- *  - floating point regs: the kernel doesn't change those
- *  - r9-15: saved by the C compiler
+ * We don't HAVE_REGS_AND_STACK_ACCESS_API.
  *
- * This makes "fork()" and "exec()" a bit more complex, but should
- * give us low system call latency.
+ * Provide empty pt_regs structure for libbpf and the likes
+ * to avoid breaking the compilation.
  */
-
 struct pt_regs {
-	unsigned long r0;
-	unsigned long r1;
-	unsigned long r2;
-	unsigned long r3;
-	unsigned long r4;
-	unsigned long r5;
-	unsigned long r6;
-	unsigned long r7;
-	unsigned long r8;
-	unsigned long r19;
-	unsigned long r20;
-	unsigned long r21;
-	unsigned long r22;
-	unsigned long r23;
-	unsigned long r24;
-	unsigned long r25;
-	unsigned long r26;
-	unsigned long r27;
-	unsigned long r28;
-	unsigned long hae;
-/* JRP - These are the values provided to a0-a2 by PALcode */
-	unsigned long trap_a0;
-	unsigned long trap_a1;
-	unsigned long trap_a2;
-/* These are saved by PAL-code: */
-	unsigned long ps;
-	unsigned long pc;
-	unsigned long gp;
-	unsigned long r16;
-	unsigned long r17;
-	unsigned long r18;
 };
 
-/*
- * This is the extended stack used by signal handlers and the context
- * switcher: it's pushed after the normal "struct pt_regs".
- */
-struct switch_stack {
-	unsigned long r9;
-	unsigned long r10;
-	unsigned long r11;
-	unsigned long r12;
-	unsigned long r13;
-	unsigned long r14;
-	unsigned long r15;
-	unsigned long r26;
-#ifndef __KERNEL__
-	unsigned long fp[32];	/* fp[31] is fpcr */
-#endif
-};
-
-
 #endif /* _UAPI_ASMAXP_PTRACE_H */
-- 
2.39.5