4 files changed, 40 insertions, 11 deletions

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index 225b0988043a..ab456dc233b5 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -15,6 +15,7 @@
 
 /* loadflags */
 #define LOADED_HIGH     (1<<0)
+#define KASLR_FLAG      (1<<1)
 #define QUIET_FLAG      (1<<5)
 #define KEEP_SEGMENTS   (1<<6)
 #define CAN_USE_HEAP    (1<<7)
diff --git a/arch/x86/include/uapi/asm/ptrace-abi.h b/arch/x86/include/uapi/asm/ptrace-abi.h
index 7b0a55a88851..580aee3072e0 100644
--- a/arch/x86/include/uapi/asm/ptrace-abi.h
+++ b/arch/x86/include/uapi/asm/ptrace-abi.h
@@ -25,13 +25,17 @@
 #else /* __i386__ */
 
 #if defined(__ASSEMBLY__) || defined(__FRAME_OFFSETS)
+/*
+ * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
+ * unless syscall needs a complete, fully filled "struct pt_regs".
+ */
 #define R15 0
 #define R14 8
 #define R13 16
 #define R12 24
 #define RBP 32
 #define RBX 40
-/* arguments: interrupts/non tracing syscalls only save up to here*/
+/* These regs are callee-clobbered. Always saved on kernel entry. */
 #define R11 48
 #define R10 56
 #define R9 64
@@ -41,15 +45,17 @@
 #define RDX 96
 #define RSI 104
 #define RDI 112
-#define ORIG_RAX 120       /* = ERROR */
-/* end of arguments */
-/* cpu exception frame or undefined in case of fast syscall. */
+/*
+ * On syscall entry, this is syscall#. On CPU exception, this is error code.
+ * On hw interrupt, it's IRQ number:
+ */
+#define ORIG_RAX 120
+/* Return frame for iretq */
 #define RIP 128
 #define CS 136
 #define EFLAGS 144
 #define RSP 152
 #define SS 160
-#define ARGOFFSET R11
 #endif /* __ASSEMBLY__ */
 
 /* top of stack page */
diff --git a/arch/x86/include/uapi/asm/ptrace.h b/arch/x86/include/uapi/asm/ptrace.h
index ac4b9aa4d999..bc16115af39b 100644
--- a/arch/x86/include/uapi/asm/ptrace.h
+++ b/arch/x86/include/uapi/asm/ptrace.h
@@ -41,13 +41,17 @@ struct pt_regs {
 #ifndef __KERNEL__
 
 struct pt_regs {
+/*
+ * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
+ * unless syscall needs a complete, fully filled "struct pt_regs".
+ */
         unsigned long r15;
         unsigned long r14;
         unsigned long r13;
         unsigned long r12;
         unsigned long rbp;
         unsigned long rbx;
-/* arguments: non interrupts/non tracing syscalls only save up to here*/
+/* These regs are callee-clobbered. Always saved on kernel entry. */
         unsigned long r11;
         unsigned long r10;
         unsigned long r9;
@@ -57,9 +61,12 @@ struct pt_regs {
         unsigned long rdx;
         unsigned long rsi;
         unsigned long rdi;
+/*
+ * On syscall entry, this is syscall#. On CPU exception, this is error code.
+ * On hw interrupt, it's IRQ number:
+ */
         unsigned long orig_rax;
-/* end of arguments */
-/* cpu exception frame or undefined */
+/* Return frame for iretq */
         unsigned long rip;
         unsigned long cs;
         unsigned long eflags;
diff --git a/arch/x86/include/uapi/asm/sigcontext.h b/arch/x86/include/uapi/asm/sigcontext.h
index d8b9f9081e86..16dc4e8a2cd3 100644
--- a/arch/x86/include/uapi/asm/sigcontext.h
+++ b/arch/x86/include/uapi/asm/sigcontext.h
@@ -177,9 +177,24 @@ struct sigcontext {
         __u64 rip;
         __u64 eflags;           /* RFLAGS */
         __u16 cs;
-        __u16 gs;
-        __u16 fs;
-        __u16 __pad0;
+
+        /*
+         * Prior to 2.5.64 ("[PATCH] x86-64 updates for 2.5.64-bk3"),
+         * Linux saved and restored fs and gs in these slots.  This
+         * was counterproductive, as fsbase and gsbase were never
+         * saved, so arch_prctl was presumably unreliable.
+         *
+         * If these slots are ever needed for any other purpose, there
+         * is some risk that very old 64-bit binaries could get
+         * confused.  I doubt that many such binaries still work,
+         * though, since the same patch in 2.5.64 also removed the
+         * 64-bit set_thread_area syscall, so it appears that there is
+         * no TLS API that works in both pre- and post-2.5.64 kernels.
+         */
+        __u16 __pad2;           /* Was gs. */
+        __u16 __pad1;           /* Was fs. */
+
+        __u16 ss;
         __u64 err;
         __u64 trapno;
         __u64 oldmask;