x86/syscall/64: Move 64-bit syscall dispatch code

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

No functional changes.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20250314151220.862768-4-brgerst@gmail.com

diff --git a/arch/x86/entry/Makefile b/arch/x86/entry/Makefile
index 96a6b86e0a8bb74035224ba103d70a028b175a62..5fd28abfd5a01e77bf7cedbc734c1b42541814a1 100644 (file)
--- 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 183efabefe57a6b117b15fc7b3624deccdcd8952..5bd448c0664f2215dd553bc078be1d368e05d7d1 100644 (file)
--- 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 ba8354424860cb48162a16f46150f706727b5c02..e0c62d5a397c30eb9ccde40461f22fe9b7428deb 100644 (file)
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -1,10 +1,12 @@
-// SPDX-License-Identifier: GPL-2.0
-/* System call table for x86-64. */
+// SPDX-License-Identifier: GPL-2.0-only
+/* 64-bit system call dispatch */
 
 #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 +36,93 @@ 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;
+}