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Diffstat (limited to 'arch/x86/entry/common.c')
-rw-r--r--arch/x86/entry/common.c49
1 files changed, 46 insertions, 3 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index bd3f14175193..e83b3f14897c 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -45,6 +45,32 @@
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
+/* Check that the stack and regs on entry from user mode are sane. */
+static void check_user_regs(struct pt_regs *regs)
+{
+ if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
+ /*
+ * Make sure that the entry code gave us a sensible EFLAGS
+ * register. Native because we want to check the actual CPU
+ * state, not the interrupt state as imagined by Xen.
+ */
+ unsigned long flags = native_save_fl();
+ WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
+ X86_EFLAGS_NT));
+
+ /* We think we came from user mode. Make sure pt_regs agrees. */
+ WARN_ON_ONCE(!user_mode(regs));
+
+ /*
+ * All entries from user mode (except #DF) should be on the
+ * normal thread stack and should have user pt_regs in the
+ * correct location.
+ */
+ WARN_ON_ONCE(!on_thread_stack());
+ WARN_ON_ONCE(regs != task_pt_regs(current));
+ }
+}
+
#ifdef CONFIG_CONTEXT_TRACKING
/**
* enter_from_user_mode - Establish state when coming from user mode
@@ -127,9 +153,6 @@ static long syscall_trace_enter(struct pt_regs *regs)
unsigned long ret = 0;
u32 work;
- if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
- BUG_ON(regs != task_pt_regs(current));
-
work = READ_ONCE(ti->flags);
if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
@@ -346,6 +369,8 @@ __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
{
struct thread_info *ti;
+ check_user_regs(regs);
+
enter_from_user_mode();
instrumentation_begin();
@@ -409,6 +434,8 @@ static void do_syscall_32_irqs_on(struct pt_regs *regs)
/* Handles int $0x80 */
__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
{
+ check_user_regs(regs);
+
enter_from_user_mode();
instrumentation_begin();
@@ -460,6 +487,8 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
vdso_image_32.sym_int80_landing_pad;
bool success;
+ check_user_regs(regs);
+
/*
* SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
* so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
@@ -510,6 +539,18 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
#endif
}
+
+/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
+__visible noinstr long do_SYSENTER_32(struct pt_regs *regs)
+{
+ /* SYSENTER loses RSP, but the vDSO saved it in RBP. */
+ regs->sp = regs->bp;
+
+ /* SYSENTER clobbers EFLAGS.IF. Assume it was set in usermode. */
+ regs->flags |= X86_EFLAGS_IF;
+
+ return do_fast_syscall_32(regs);
+}
#endif
SYSCALL_DEFINE0(ni_syscall)
@@ -553,6 +594,7 @@ SYSCALL_DEFINE0(ni_syscall)
bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
{
if (user_mode(regs)) {
+ check_user_regs(regs);
enter_from_user_mode();
return false;
}
@@ -686,6 +728,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
*/
void noinstr idtentry_enter_user(struct pt_regs *regs)
{
+ check_user_regs(regs);
enter_from_user_mode();
}