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Date: Fri, 14 May 2021 18:10:15 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 4/4] x86/syscall: use int everywhere for system call numbers
From: "H. Peter Anvin (Intel)" <hpa@...or.com>
System call numbers are defined as int, so use int everywhere for
system call numbers. This patch is strictly a cleanup; it should not
change anything user visible; all ABI changes have been done in the
preceeding patches.
Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
arch/x86/entry/common.c | 93 ++++++++++++++++++++++++----------
arch/x86/include/asm/syscall.h | 2 +-
2 files changed, 66 insertions(+), 29 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index f51bc17262db..714804f0970c 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -36,49 +36,87 @@
#include <asm/irq_stack.h>
#ifdef CONFIG_X86_64
-__visible noinstr void do_syscall_64(struct pt_regs *regs, unsigned long nr)
+
+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. Use unsigned long to slightly
+ * improve the array_index_nospec() generated code.
+ */
+ unsigned long unr = nr;
+
+ if (likely(unr < NR_syscalls)) {
+ unr = array_index_nospec(unr, NR_syscalls);
+ regs->ax = sys_call_table[unr](regs);
+ 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. Use unsigned long to slightly
+ * improve the array_index_nospec() generated code.
+ */
+ unsigned long 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_table[xnr](regs);
+ return true;
+ }
+ return false;
+}
+
+__visible noinstr void do_syscall_64(struct pt_regs *regs, int nr)
{
add_random_kstack_offset();
nr = syscall_enter_from_user_mode(regs, nr);
instrumentation_begin();
- if (likely(nr < NR_syscalls)) {
- nr = array_index_nospec(nr, NR_syscalls);
- regs->ax = sys_call_table[nr](regs);
-#ifdef CONFIG_X86_X32_ABI
- } else if (likely((nr & __X32_SYSCALL_BIT) &&
- (nr & ~__X32_SYSCALL_BIT) < X32_NR_syscalls)) {
- nr = array_index_nospec(nr & ~__X32_SYSCALL_BIT,
- X32_NR_syscalls);
- regs->ax = x32_sys_call_table[nr](regs);
-#endif
- } else if (unlikely((int)nr != -1)) {
+
+ if (!do_syscall_x64(regs, nr) &&
+ !do_syscall_x32(regs, nr) &&
+ unlikely(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);
}
#endif
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
-static __always_inline unsigned int syscall_32_enter(struct pt_regs *regs)
+static __always_inline int syscall_32_enter(struct pt_regs *regs)
{
if (IS_ENABLED(CONFIG_IA32_EMULATION))
current_thread_info()->status |= TS_COMPAT;
- return (unsigned int)regs->orig_ax;
+ return (int)regs->orig_ax;
}
/*
* Invoke a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL.
*/
-static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs,
- unsigned int nr)
+static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr)
{
- if (likely(nr < IA32_NR_syscalls)) {
- nr = array_index_nospec(nr, IA32_NR_syscalls);
- regs->ax = ia32_sys_call_table[nr](regs);
- } else if (unlikely((int)nr != -1)) {
+ /*
+ * Convert negative numbers to very high and thus out of range
+ * numbers for comparisons. Use unsigned long to slightly
+ * improve the array_index_nospec() generated code.
+ */
+ unsigned long unr = nr;
+
+ if (likely(unr < IA32_NR_syscalls)) {
+ unr = array_index_nospec(unr, IA32_NR_syscalls);
+ regs->ax = ia32_sys_call_table[unr](regs);
+ } else if (unlikely(nr != -1)) {
regs->ax = __ia32_sys_ni_syscall(regs);
}
}
@@ -86,15 +124,15 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs,
/* Handles int $0x80 */
__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
{
- unsigned int nr = syscall_32_enter(regs);
+ int nr = syscall_32_enter(regs);
add_random_kstack_offset();
/*
- * Subtlety here: if ptrace pokes something larger than 2^32-1 into
- * orig_ax, the unsigned int return value truncates it. This may
- * or may not be necessary, but it matches the old asm behavior.
+ * Subtlety here: if ptrace pokes something larger than 2^31-1 into
+ * orig_ax, the int return value truncates it. This matches
+ * the semantics of syscall_get_nr().
*/
- nr = (unsigned int)syscall_enter_from_user_mode(regs, nr);
+ nr = syscall_enter_from_user_mode(regs, nr);
instrumentation_begin();
do_syscall_32_irqs_on(regs, nr);
@@ -105,7 +143,7 @@ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
{
- unsigned int nr = syscall_32_enter(regs);
+ int nr = syscall_32_enter(regs);
int res;
add_random_kstack_offset();
@@ -140,8 +178,7 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
return false;
}
- /* The case truncates any ptrace induced syscall nr > 2^32 -1 */
- nr = (unsigned int)syscall_enter_from_user_mode_work(regs, nr);
+ nr = syscall_enter_from_user_mode_work(regs, nr);
/* Now this is just like a normal syscall. */
do_syscall_32_irqs_on(regs, nr);
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index f6593cafdbd9..f7e2d82d24fb 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -159,7 +159,7 @@ static inline int syscall_get_arch(struct task_struct *task)
? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
}
-void do_syscall_64(struct pt_regs *regs, unsigned long nr);
+void do_syscall_64(struct pt_regs *regs, int nr);
void do_int80_syscall_32(struct pt_regs *regs);
long do_fast_syscall_32(struct pt_regs *regs);
--
2.31.1
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