[PATCH v2 1/3] syscalls,x86 Expose arch_prctl on x86-32.

[Kyle Huey <me@kylehuey.com>]

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 arch/x86/entry/syscalls/syscall_32.tbl |  1 +
 arch/x86/kernel/process.c              | 80 ++++++++++++++++++++++++++++++++++
 arch/x86/kernel/process_64.c           | 66 ----------------------------
 3 files changed, 81 insertions(+), 66 deletions(-)

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index f848572..3b6965b 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -386,3 +386,4 @@
 377	i386	copy_file_range		sys_copy_file_range
 378	i386	preadv2			sys_preadv2			compat_sys_preadv2
 379	i386	pwritev2		sys_pwritev2			compat_sys_pwritev2
+380	i386	arch_prctl		sys_arch_prctl
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 62c0b0e..0f857c3 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -20,6 +20,7 @@
 #include <linux/cpuidle.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
+#include <linux/syscalls.h>
 #include <asm/cpu.h>
 #include <asm/apic.h>
 #include <asm/syscalls.h>
@@ -32,6 +33,7 @@
 #include <asm/tlbflush.h>
 #include <asm/mce.h>
 #include <asm/vm86.h>
+#include <asm/prctl.h>
 
 /*
  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -567,3 +569,81 @@ unsigned long get_wchan(struct task_struct *p)
 	} while (count++ < 16 && p->state != TASK_RUNNING);
 	return 0;
 }
+
+long do_arch_prctl(struct task_struct *task, int code, unsigned long arg2)
+{
+	int ret = 0;
+	int doit = task == current;
+	int is_32 = IS_ENABLED(CONFIG_IA32_EMULATION) && test_thread_flag(TIF_IA32);
+	int cpu;
+
+	switch (code) {
+#ifdef CONFIG_X86_64
+	case ARCH_SET_GS:
+		if (is_32)
+			return -EINVAL;
+		if (arg2 >= TASK_SIZE_MAX)
+			return -EPERM;
+		cpu = get_cpu();
+		task->thread.gsindex = 0;
+		task->thread.gsbase = arg2;
+		if (doit) {
+			load_gs_index(0);
+			ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, arg2);
+		}
+		put_cpu();
+		break;
+	case ARCH_SET_FS:
+		if (is_32)
+			return -EINVAL;
+		/* Not strictly needed for fs, but do it for symmetry
+		   with gs */
+		if (arg2 >= TASK_SIZE_MAX)
+			return -EPERM;
+		cpu = get_cpu();
+		task->thread.fsindex = 0;
+		task->thread.fsbase = arg2;
+		if (doit) {
+			/* set the selector to 0 to not confuse __switch_to */
+			loadsegment(fs, 0);
+			ret = wrmsrl_safe(MSR_FS_BASE, arg2);
+		}
+		put_cpu();
+		break;
+	case ARCH_GET_FS: {
+		unsigned long base;
+
+		if (is_32)
+			return -EINVAL;
+		if (doit)
+			rdmsrl(MSR_FS_BASE, base);
+		else
+			base = task->thread.fsbase;
+		ret = put_user(base, (unsigned long __user *)arg2);
+		break;
+	}
+	case ARCH_GET_GS: {
+		unsigned long base;
+
+		if (is_32)
+			return -EINVAL;
+		if (doit)
+			rdmsrl(MSR_KERNEL_GS_BASE, base);
+		else
+			base = task->thread.gsbase;
+		ret = put_user(base, (unsigned long __user *)arg2);
+		break;
+	}
+#endif
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
+{
+	return do_arch_prctl(current, code, arg2);
+}
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 63236d8..e8c6302 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -524,72 +524,6 @@ void set_personality_ia32(bool x32)
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);
 
-long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
-{
-	int ret = 0;
-	int doit = task == current;
-	int cpu;
-
-	switch (code) {
-	case ARCH_SET_GS:
-		if (addr >= TASK_SIZE_MAX)
-			return -EPERM;
-		cpu = get_cpu();
-		task->thread.gsindex = 0;
-		task->thread.gsbase = addr;
-		if (doit) {
-			load_gs_index(0);
-			ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, addr);
-		}
-		put_cpu();
-		break;
-	case ARCH_SET_FS:
-		/* Not strictly needed for fs, but do it for symmetry
-		   with gs */
-		if (addr >= TASK_SIZE_MAX)
-			return -EPERM;
-		cpu = get_cpu();
-		task->thread.fsindex = 0;
-		task->thread.fsbase = addr;
-		if (doit) {
-			/* set the selector to 0 to not confuse __switch_to */
-			loadsegment(fs, 0);
-			ret = wrmsrl_safe(MSR_FS_BASE, addr);
-		}
-		put_cpu();
-		break;
-	case ARCH_GET_FS: {
-		unsigned long base;
-		if (doit)
-			rdmsrl(MSR_FS_BASE, base);
-		else
-			base = task->thread.fsbase;
-		ret = put_user(base, (unsigned long __user *)addr);
-		break;
-	}
-	case ARCH_GET_GS: {
-		unsigned long base;
-		if (doit)
-			rdmsrl(MSR_KERNEL_GS_BASE, base);
-		else
-			base = task->thread.gsbase;
-		ret = put_user(base, (unsigned long __user *)addr);
-		break;
-	}
-
-	default:
-		ret = -EINVAL;
-		break;
-	}
-
-	return ret;
-}
-
-long sys_arch_prctl(int code, unsigned long addr)
-{
-	return do_arch_prctl(current, code, addr);
-}
-
 unsigned long KSTK_ESP(struct task_struct *task)
 {
 	return task_pt_regs(task)->sp;
-- 
2.7.4