[PATCH 3/5] x86/syscall/64: Move 64-bit syscall dispatch code

[Brian Gerst <brgerst@gmail.com>]

Move the 64-bit syscall dispatch code to syscall_64.c.

No functional changes.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
 arch/x86/entry/Makefile     |   2 +
 arch/x86/entry/common.c     |  93 --------------------------------
 arch/x86/entry/syscall_64.c | 103 +++++++++++++++++++++++++++++++++++-
 3 files changed, 103 insertions(+), 95 deletions(-)

diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile
index 96a6b86e0a8b..5fd28abfd5a0 100644
--- a/arch/x86/entry/Makefile
+++ b/arch/x86/entry/Makefile
@@ -9,9 +9,11 @@ KCOV_INSTRUMENT := n
 
 CFLAGS_REMOVE_common.o		= $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_syscall_32.o	= $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_syscall_64.o	= $(CC_FLAGS_FTRACE)
 
 CFLAGS_common.o			+= -fno-stack-protector
 CFLAGS_syscall_32.o		+= -fno-stack-protector
+CFLAGS_syscall_64.o		+= -fno-stack-protector
 
 obj-y				:= entry.o entry_$(BITS).o syscall_$(BITS).o
 obj-y				+= common.o
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 183efabefe57..5bd448c0664f 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -32,99 +32,6 @@
 #include <asm/syscall.h>
 #include <asm/irq_stack.h>
 
-#ifdef CONFIG_X86_64
-
-static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr)
-{
-	/*
-	 * Convert negative numbers to very high and thus out of range
-	 * numbers for comparisons.
-	 */
-	unsigned int unr = nr;
-
-	if (likely(unr < NR_syscalls)) {
-		unr = array_index_nospec(unr, NR_syscalls);
-		regs->ax = x64_sys_call(regs, unr);
-		return true;
-	}
-	return false;
-}
-
-static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
-{
-	/*
-	 * Adjust the starting offset of the table, and convert numbers
-	 * < __X32_SYSCALL_BIT to very high and thus out of range
-	 * numbers for comparisons.
-	 */
-	unsigned int xnr = nr - __X32_SYSCALL_BIT;
-
-	if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) {
-		xnr = array_index_nospec(xnr, X32_NR_syscalls);
-		regs->ax = x32_sys_call(regs, xnr);
-		return true;
-	}
-	return false;
-}
-
-/* Returns true to return using SYSRET, or false to use IRET */
-__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr)
-{
-	add_random_kstack_offset();
-	nr = syscall_enter_from_user_mode(regs, nr);
-
-	instrumentation_begin();
-
-	if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) {
-		/* Invalid system call, but still a system call. */
-		regs->ax = __x64_sys_ni_syscall(regs);
-	}
-
-	instrumentation_end();
-	syscall_exit_to_user_mode(regs);
-
-	/*
-	 * Check that the register state is valid for using SYSRET to exit
-	 * to userspace.  Otherwise use the slower but fully capable IRET
-	 * exit path.
-	 */
-
-	/* XEN PV guests always use the IRET path */
-	if (cpu_feature_enabled(X86_FEATURE_XENPV))
-		return false;
-
-	/* SYSRET requires RCX == RIP and R11 == EFLAGS */
-	if (unlikely(regs->cx != regs->ip || regs->r11 != regs->flags))
-		return false;
-
-	/* CS and SS must match the values set in MSR_STAR */
-	if (unlikely(regs->cs != __USER_CS || regs->ss != __USER_DS))
-		return false;
-
-	/*
-	 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
-	 * in kernel space.  This essentially lets the user take over
-	 * the kernel, since userspace controls RSP.
-	 *
-	 * TASK_SIZE_MAX covers all user-accessible addresses other than
-	 * the deprecated vsyscall page.
-	 */
-	if (unlikely(regs->ip >= TASK_SIZE_MAX))
-		return false;
-
-	/*
-	 * SYSRET cannot restore RF.  It can restore TF, but unlike IRET,
-	 * restoring TF results in a trap from userspace immediately after
-	 * SYSRET.
-	 */
-	if (unlikely(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)))
-		return false;
-
-	/* Use SYSRET to exit to userspace */
-	return true;
-}
-#endif
-
 SYSCALL_DEFINE0(ni_syscall)
 {
 	return -ENOSYS;
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index ba8354424860..9e0ba339013c 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -1,10 +1,19 @@
-// SPDX-License-Identifier: GPL-2.0
-/* System call table for x86-64. */
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 64-bit system call dispatch
+ *
+ * Copyright (c) 2015 Andrew Lutomirski
+ *
+ * Based on asm and ptrace code by many authors.  The code here originated
+ * in ptrace.c and signal.c.
+ */
 
 #include <linux/linkage.h>
 #include <linux/sys.h>
 #include <linux/cache.h>
 #include <linux/syscalls.h>
+#include <linux/entry-common.h>
+#include <linux/nospec.h>
 #include <asm/syscall.h>
 
 #define __SYSCALL(nr, sym) extern long __x64_##sym(const struct pt_regs *);
@@ -34,3 +43,93 @@ long x64_sys_call(const struct pt_regs *regs, unsigned int nr)
 	default: return __x64_sys_ni_syscall(regs);
 	}
 };
+
+static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr)
+{
+	/*
+	 * Convert negative numbers to very high and thus out of range
+	 * numbers for comparisons.
+	 */
+	unsigned int unr = nr;
+
+	if (likely(unr < NR_syscalls)) {
+		unr = array_index_nospec(unr, NR_syscalls);
+		regs->ax = x64_sys_call(regs, unr);
+		return true;
+	}
+	return false;
+}
+
+static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr)
+{
+	/*
+	 * Adjust the starting offset of the table, and convert numbers
+	 * < __X32_SYSCALL_BIT to very high and thus out of range
+	 * numbers for comparisons.
+	 */
+	unsigned int xnr = nr - __X32_SYSCALL_BIT;
+
+	if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) {
+		xnr = array_index_nospec(xnr, X32_NR_syscalls);
+		regs->ax = x32_sys_call(regs, xnr);
+		return true;
+	}
+	return false;
+}
+
+/* Returns true to return using SYSRET, or false to use IRET */
+__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr)
+{
+	add_random_kstack_offset();
+	nr = syscall_enter_from_user_mode(regs, nr);
+
+	instrumentation_begin();
+
+	if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) {
+		/* Invalid system call, but still a system call. */
+		regs->ax = __x64_sys_ni_syscall(regs);
+	}
+
+	instrumentation_end();
+	syscall_exit_to_user_mode(regs);
+
+	/*
+	 * Check that the register state is valid for using SYSRET to exit
+	 * to userspace.  Otherwise use the slower but fully capable IRET
+	 * exit path.
+	 */
+
+	/* XEN PV guests always use the IRET path */
+	if (cpu_feature_enabled(X86_FEATURE_XENPV))
+		return false;
+
+	/* SYSRET requires RCX == RIP and R11 == EFLAGS */
+	if (unlikely(regs->cx != regs->ip || regs->r11 != regs->flags))
+		return false;
+
+	/* CS and SS must match the values set in MSR_STAR */
+	if (unlikely(regs->cs != __USER_CS || regs->ss != __USER_DS))
+		return false;
+
+	/*
+	 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
+	 * in kernel space.  This essentially lets the user take over
+	 * the kernel, since userspace controls RSP.
+	 *
+	 * TASK_SIZE_MAX covers all user-accessible addresses other than
+	 * the deprecated vsyscall page.
+	 */
+	if (unlikely(regs->ip >= TASK_SIZE_MAX))
+		return false;
+
+	/*
+	 * SYSRET cannot restore RF.  It can restore TF, but unlike IRET,
+	 * restoring TF results in a trap from userspace immediately after
+	 * SYSRET.
+	 */
+	if (unlikely(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)))
+		return false;
+
+	/* Use SYSRET to exit to userspace */
+	return true;
+}
-- 
2.48.1