linux-kernel - [RFC PATCH 7/7] sci: add example system calls to exercse SCI

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Message-Id: <1556228754-12996-8-git-send-email-rppt@linux.ibm.com>
Date:   Fri, 26 Apr 2019 00:45:54 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     Alexandre Chartre <alexandre.chartre@...cle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Jonathan Adams <jwadams@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Turner <pjt@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, linux-mm@...ck.org,
        linux-security-module@...r.kernel.org, x86@...nel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: [RFC PATCH 7/7] sci: add example system calls to exercse SCI

Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
 arch/x86/entry/common.c                |  6 +++-
 arch/x86/entry/syscalls/syscall_64.tbl |  3 ++
 kernel/Makefile                        |  2 +-
 kernel/sci-examples.c                  | 52 ++++++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 kernel/sci-examples.c

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 8f2a6fd..be0e1a7 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -275,7 +275,11 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs)
 #ifdef CONFIG_SYSCALL_ISOLATION
 static inline bool sci_required(unsigned long nr)
 {
-	return false;
+	if (!static_cpu_has(X86_FEATURE_SCI))
+		return false;
+	if (nr < __NR_get_answer)
+		return false;
+	return true;
 }
 
 static inline unsigned long sci_syscall_enter(unsigned long nr)
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index f0b1709..a25e838 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -343,6 +343,9 @@
 332	common	statx			__x64_sys_statx
 333	common	io_pgetevents		__x64_sys_io_pgetevents
 334	common	rseq			__x64_sys_rseq
+335	64	get_answer		__x64_sys_get_answer
+336	64	sci_write_dmesg		__x64_sys_sci_write_dmesg
+337	64	sci_write_dmesg_bad	__x64_sys_sci_write_dmesg_bad
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/kernel/Makefile b/kernel/Makefile
index 6aa7543..d6441d0 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y     = fork.o exec_domain.o panic.o \
 	    extable.o params.o \
 	    kthread.o sys_ni.o nsproxy.o \
 	    notifier.o ksysfs.o cred.o reboot.o \
-	    async.o range.o smpboot.o ucount.o
+	    async.o range.o smpboot.o ucount.o sci-examples.o
 
 obj-$(CONFIG_MODULES) += kmod.o
 obj-$(CONFIG_MULTIUSER) += groups.o
diff --git a/kernel/sci-examples.c b/kernel/sci-examples.c
new file mode 100644
index 0000000..9bfaad0
--- /dev/null
+++ b/kernel/sci-examples.c
@@ -0,0 +1,52 @@
+#include <linux/kernel.h>
+#include <linux/pid.h>
+#include <linux/syscalls.h>
+#include <linux/hugetlb.h>
+#include <asm/special_insns.h>
+
+SYSCALL_DEFINE0(get_answer)
+{
+	return 42;
+}
+
+#define BUF_SIZE 1024
+
+typedef void (*foo)(void);
+
+SYSCALL_DEFINE2(sci_write_dmesg, const char __user *, ubuf, size_t, count)
+{
+	char buf[BUF_SIZE];
+
+	if (!ubuf || count >= BUF_SIZE)
+		return -EINVAL;
+
+	buf[count] = '\0';
+	if (copy_from_user(buf, ubuf, count))
+		return -EFAULT;
+
+	printk("%s\n", buf);
+
+	return count;
+}
+
+SYSCALL_DEFINE2(sci_write_dmesg_bad, const char __user *, ubuf, size_t, count)
+{
+	unsigned long addr = (unsigned long)(void *)hugetlb_reserve_pages;
+	char buf[BUF_SIZE];
+	foo func1;
+
+	addr += 0xc5;
+	func1 = (foo)(void *)addr;
+	func1();
+
+	if (!ubuf || count >= BUF_SIZE)
+		return -EINVAL;
+
+	buf[count] = '\0';
+	if (copy_from_user(buf, ubuf, count))
+		return -EFAULT;
+
+	printk("%s\n", buf);
+
+	return count;
+}
-- 
2.7.4