System calls are really quite simple. Add a helper to call
a 32-bit system call.
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
arch/x86/entry/common.c | 43 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index d94a60c16029..41d17508cf46 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -318,3 +318,46 @@ __visible void syscall_return_slowpath(struct pt_regs
*regs)
local_irq_disable();
prepare_exit_to_usermode(regs);
}
+
+#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
+/*
+ * Does a 32-bit syscall. Called with IRQs off and does all entry and
+ * exit work.
+ */
+__visible void do_int80_syscall_32(struct pt_regs *regs)
+{
+ struct thread_info *ti = pt_regs_to_thread_info(regs);
+ unsigned int nr = (unsigned int)regs->orig_ax;
+
+#ifdef CONFIG_IA32_EMULATION
+ ti->status |= TS_COMPAT;
+#endif
+
+ local_irq_enable();
+
+ if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
+ /*
+ * Subtlety here: if ptrace pokes something larger than
+ * 2^32-1 into orig_ax, this truncates it. This may or
+ * may not be necessary, but it matches the old asm
+ * behavior.
+ */
+ nr = syscall_trace_enter(regs);
+ }
+
+ if (nr < IA32_NR_syscalls) {
+ /*
+ * It's possible that a 32-bit syscall implementation
+ * takes a 64-bit parameter but nonetheless assumes that
+ * the high bits are zero. Make sure we zero-extend all
+ * of the args.
+ */
+ regs->ax = ia32_sys_call_table[nr](
+ (unsigned int)regs->bx, (unsigned int)regs->cx,
+ (unsigned int)regs->dx, (unsigned int)regs->si,
+ (unsigned int)regs->di, (unsigned int)regs->bp);
+ }
+
+ syscall_return_slowpath(regs);
+}
+#endif
--
2.4.3
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