1 files changed, 39 insertions, 14 deletions

diff --git a/arch/arm/syscall_arch.h b/arch/arm/syscall_arch.h
index 6023303b..4db7d152 100644
--- a/arch/arm/syscall_arch.h
+++ b/arch/arm/syscall_arch.h
@@ -3,74 +3,99 @@
 ((union { long long ll; long l[2]; }){ .ll = x }).l[1]
 #define __SYSCALL_LL_O(x) 0, __SYSCALL_LL_E((x))
 
+#ifdef __thumb__
+
+/* Avoid use of r7 in asm constraints when producing thumb code,
+ * since it's reserved as frame pointer and might not be supported. */
+#define __ASM____R7__
+#define __asm_syscall(...) do { \
+	__asm__ __volatile__ ( "mov %1,r7 ; mov r7,%2 ; svc 0 ; mov r7,%1" \
+	: "=r"(r0), "=&r"((int){0}) : __VA_ARGS__ : "memory"); \
+	return r0; \
+	} while (0)
+
+#else
+
+#define __ASM____R7__ __asm__("r7")
 #define __asm_syscall(...) do { \
 	__asm__ __volatile__ ( "svc 0" \
 	: "=r"(r0) : __VA_ARGS__ : "memory"); \
 	return r0; \
 	} while (0)
+#endif
+
+/* For thumb2, we can allow 8-bit immediate syscall numbers, saving a
+ * register in the above dance around r7. Does not work for thumb1 where
+ * only movs, not mov, supports immediates, and we can't use movs because
+ * it doesn't support high regs. */
+#ifdef __thumb2__
+#define R7_OPERAND "rI"(r7)
+#else
+#define R7_OPERAND "r"(r7)
+#endif
 
 static inline long __syscall0(long n)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0");
-	__asm_syscall("r"(r7));
+	__asm_syscall(R7_OPERAND);
 }
 
 static inline long __syscall1(long n, long a)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
-	__asm_syscall("r"(r7), "0"(r0));
+	__asm_syscall(R7_OPERAND, "0"(r0));
 }
 
 static inline long __syscall2(long n, long a, long b)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
 	register long r1 __asm__("r1") = b;
-	__asm_syscall("r"(r7), "0"(r0), "r"(r1));
+	__asm_syscall(R7_OPERAND, "0"(r0), "r"(r1));
 }
 
 static inline long __syscall3(long n, long a, long b, long c)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
 	register long r1 __asm__("r1") = b;
 	register long r2 __asm__("r2") = c;
-	__asm_syscall("r"(r7), "0"(r0), "r"(r1), "r"(r2));
+	__asm_syscall(R7_OPERAND, "0"(r0), "r"(r1), "r"(r2));
 }
 
 static inline long __syscall4(long n, long a, long b, long c, long d)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
 	register long r1 __asm__("r1") = b;
 	register long r2 __asm__("r2") = c;
 	register long r3 __asm__("r3") = d;
-	__asm_syscall("r"(r7), "0"(r0), "r"(r1), "r"(r2), "r"(r3));
+	__asm_syscall(R7_OPERAND, "0"(r0), "r"(r1), "r"(r2), "r"(r3));
 }
 
 static inline long __syscall5(long n, long a, long b, long c, long d, long e)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
 	register long r1 __asm__("r1") = b;
 	register long r2 __asm__("r2") = c;
 	register long r3 __asm__("r3") = d;
 	register long r4 __asm__("r4") = e;
-	__asm_syscall("r"(r7), "0"(r0), "r"(r1), "r"(r2), "r"(r3), "r"(r4));
+	__asm_syscall(R7_OPERAND, "0"(r0), "r"(r1), "r"(r2), "r"(r3), "r"(r4));
 }
 
 static inline long __syscall6(long n, long a, long b, long c, long d, long e, long f)
 {
-	register long r7 __asm__("r7") = n;
+	register long r7 __ASM____R7__ = n;
 	register long r0 __asm__("r0") = a;
 	register long r1 __asm__("r1") = b;
 	register long r2 __asm__("r2") = c;
 	register long r3 __asm__("r3") = d;
 	register long r4 __asm__("r4") = e;
 	register long r5 __asm__("r5") = f;
-	__asm_syscall("r"(r7), "0"(r0), "r"(r1), "r"(r2), "r"(r3), "r"(r4), "r"(r5));
+	__asm_syscall(R7_OPERAND, "0"(r0), "r"(r1), "r"(r2), "r"(r3), "r"(r4), "r"(r5));
 }
 
 #define VDSO_USEFUL