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-rw-r--r--include/asm-x86/xen/hypercall.h170
1 files changed, 122 insertions, 48 deletions
diff --git a/include/asm-x86/xen/hypercall.h b/include/asm-x86/xen/hypercall.h
index 0551b9d82ec4..d0c5dedcb001 100644
--- a/include/asm-x86/xen/hypercall.h
+++ b/include/asm-x86/xen/hypercall.h
@@ -40,83 +40,157 @@
#include <xen/interface/sched.h>
#include <xen/interface/physdev.h>
+/*
+ * The hypercall asms have to meet several constraints:
+ * - Work on 32- and 64-bit.
+ * The two architectures put their arguments in different sets of
+ * registers.
+ *
+ * - Work around asm syntax quirks
+ * It isn't possible to specify one of the rNN registers in a
+ * constraint, so we use explicit register variables to get the
+ * args into the right place.
+ *
+ * - Mark all registers as potentially clobbered
+ * Even unused parameters can be clobbered by the hypervisor, so we
+ * need to make sure gcc knows it.
+ *
+ * - Avoid compiler bugs.
+ * This is the tricky part. Because x86_32 has such a constrained
+ * register set, gcc versions below 4.3 have trouble generating
+ * code when all the arg registers and memory are trashed by the
+ * asm. There are syntactically simpler ways of achieving the
+ * semantics below, but they cause the compiler to crash.
+ *
+ * The only combination I found which works is:
+ * - assign the __argX variables first
+ * - list all actually used parameters as "+r" (__argX)
+ * - clobber the rest
+ *
+ * The result certainly isn't pretty, and it really shows up cpp's
+ * weakness as as macro language. Sorry. (But let's just give thanks
+ * there aren't more than 5 arguments...)
+ */
+
extern struct { char _entry[32]; } hypercall_page[];
+#define __HYPERCALL "call hypercall_page+%c[offset]"
+#define __HYPERCALL_ENTRY(x) \
+ [offset] "i" (__HYPERVISOR_##x * sizeof(hypercall_page[0]))
+
+#ifdef CONFIG_X86_32
+#define __HYPERCALL_RETREG "eax"
+#define __HYPERCALL_ARG1REG "ebx"
+#define __HYPERCALL_ARG2REG "ecx"
+#define __HYPERCALL_ARG3REG "edx"
+#define __HYPERCALL_ARG4REG "esi"
+#define __HYPERCALL_ARG5REG "edi"
+#else
+#define __HYPERCALL_RETREG "rax"
+#define __HYPERCALL_ARG1REG "rdi"
+#define __HYPERCALL_ARG2REG "rsi"
+#define __HYPERCALL_ARG3REG "rdx"
+#define __HYPERCALL_ARG4REG "r10"
+#define __HYPERCALL_ARG5REG "r8"
+#endif
+
+#define __HYPERCALL_DECLS \
+ register unsigned long __res asm(__HYPERCALL_RETREG); \
+ register unsigned long __arg1 asm(__HYPERCALL_ARG1REG) = __arg1; \
+ register unsigned long __arg2 asm(__HYPERCALL_ARG2REG) = __arg2; \
+ register unsigned long __arg3 asm(__HYPERCALL_ARG3REG) = __arg3; \
+ register unsigned long __arg4 asm(__HYPERCALL_ARG4REG) = __arg4; \
+ register unsigned long __arg5 asm(__HYPERCALL_ARG5REG) = __arg5;
+
+#define __HYPERCALL_0PARAM "=r" (__res)
+#define __HYPERCALL_1PARAM __HYPERCALL_0PARAM, "+r" (__arg1)
+#define __HYPERCALL_2PARAM __HYPERCALL_1PARAM, "+r" (__arg2)
+#define __HYPERCALL_3PARAM __HYPERCALL_2PARAM, "+r" (__arg3)
+#define __HYPERCALL_4PARAM __HYPERCALL_3PARAM, "+r" (__arg4)
+#define __HYPERCALL_5PARAM __HYPERCALL_4PARAM, "+r" (__arg5)
+
+#define __HYPERCALL_0ARG()
+#define __HYPERCALL_1ARG(a1) \
+ __HYPERCALL_0ARG() __arg1 = (unsigned long)(a1);
+#define __HYPERCALL_2ARG(a1,a2) \
+ __HYPERCALL_1ARG(a1) __arg2 = (unsigned long)(a2);
+#define __HYPERCALL_3ARG(a1,a2,a3) \
+ __HYPERCALL_2ARG(a1,a2) __arg3 = (unsigned long)(a3);
+#define __HYPERCALL_4ARG(a1,a2,a3,a4) \
+ __HYPERCALL_3ARG(a1,a2,a3) __arg4 = (unsigned long)(a4);
+#define __HYPERCALL_5ARG(a1,a2,a3,a4,a5) \
+ __HYPERCALL_4ARG(a1,a2,a3,a4) __arg5 = (unsigned long)(a5);
+
+#define __HYPERCALL_CLOBBER5 "memory"
+#define __HYPERCALL_CLOBBER4 __HYPERCALL_CLOBBER5, __HYPERCALL_ARG5REG
+#define __HYPERCALL_CLOBBER3 __HYPERCALL_CLOBBER4, __HYPERCALL_ARG4REG
+#define __HYPERCALL_CLOBBER2 __HYPERCALL_CLOBBER3, __HYPERCALL_ARG3REG
+#define __HYPERCALL_CLOBBER1 __HYPERCALL_CLOBBER2, __HYPERCALL_ARG2REG
+#define __HYPERCALL_CLOBBER0 __HYPERCALL_CLOBBER1, __HYPERCALL_ARG1REG
+
#define _hypercall0(type, name) \
({ \
- long __res; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res) \
- : [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_0ARG(); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_0PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER0); \
(type)__res; \
})
#define _hypercall1(type, name, a1) \
({ \
- long __res, __ign1; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res), "=b" (__ign1) \
- : "1" ((long)(a1)), \
- [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_1ARG(a1); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_1PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER1); \
(type)__res; \
})
#define _hypercall2(type, name, a1, a2) \
({ \
- long __res, __ign1, __ign2; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res), "=b" (__ign1), "=c" (__ign2) \
- : "1" ((long)(a1)), "2" ((long)(a2)), \
- [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_2ARG(a1, a2); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_2PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER2); \
(type)__res; \
})
#define _hypercall3(type, name, a1, a2, a3) \
({ \
- long __res, __ign1, __ign2, __ign3; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res), "=b" (__ign1), "=c" (__ign2), \
- "=d" (__ign3) \
- : "1" ((long)(a1)), "2" ((long)(a2)), \
- "3" ((long)(a3)), \
- [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_3ARG(a1, a2, a3); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_3PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER3); \
(type)__res; \
})
#define _hypercall4(type, name, a1, a2, a3, a4) \
({ \
- long __res, __ign1, __ign2, __ign3, __ign4; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res), "=b" (__ign1), "=c" (__ign2), \
- "=d" (__ign3), "=S" (__ign4) \
- : "1" ((long)(a1)), "2" ((long)(a2)), \
- "3" ((long)(a3)), "4" ((long)(a4)), \
- [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_4ARG(a1, a2, a3, a4); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_4PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER4); \
(type)__res; \
})
#define _hypercall5(type, name, a1, a2, a3, a4, a5) \
({ \
- long __res, __ign1, __ign2, __ign3, __ign4, __ign5; \
- asm volatile ( \
- "call %[call]" \
- : "=a" (__res), "=b" (__ign1), "=c" (__ign2), \
- "=d" (__ign3), "=S" (__ign4), "=D" (__ign5) \
- : "1" ((long)(a1)), "2" ((long)(a2)), \
- "3" ((long)(a3)), "4" ((long)(a4)), \
- "5" ((long)(a5)), \
- [call] "m" (hypercall_page[__HYPERVISOR_##name]) \
- : "memory" ); \
+ __HYPERCALL_DECLS; \
+ __HYPERCALL_5ARG(a1, a2, a3, a4, a5); \
+ asm volatile (__HYPERCALL \
+ : __HYPERCALL_5PARAM \
+ : __HYPERCALL_ENTRY(name) \
+ : __HYPERCALL_CLOBBER5); \
(type)__res; \
})
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