解决编译“ Error: selected processor does not support ARM mode `smc #0”问题

在用arm2011.09编译器编译pandaboard的x-loader时遇到如下编译问题：

 Error: selected processor does not support ARM mode `smc #0

google了一下，貌似这样的问题还是挺多的，有几种方法，一一实验。

1.

 replacing in arch/arm/mach-omap2/Makefile:

 AFLAGS_sleep24xx.o                      :=-Wa,-march=armv6
 AFLAGS_sleep34xx.o                      :=-Wa,-march=armv7-a

 to:

 AFLAGS_sleep24xx.o                      :=-Wa,-march=armv6
 AFLAGS_sleep34xx.o                      :=-Wa,-march=armv7-a$(plus_sec)

 helps compiling (see also: https://patchwork.kernel.org/patch/369681/)

在config.mk中修改后，实验无效，

$(plus_sec)

为空，无效。

2. uboot的faq，http://www.denx.de/wiki/ELDK-5/FrequentlyAskedQuestionsAndAnswers，标题Cannot compile Linux kernel version 2.6.32 for armv7a

Question:

I want to compile a vendor-provided old Linux kernel tree (kernel version 2.6.32) with ELDK 5.0 for the armv7a configuration. Unfortunately this fails with errors like this one:

   
     
     
     
     
 ...
  CC      arch/arm/kernel/sysfs_v7.o
/tmp/ccwkv7On.s: Assembler messages:
/tmp/ccwkv7On.s:249: Error: selected processor does not support ARM mode `smc #0'
/tmp/ccwkv7On.s:289: Error: selected processor does not support ARM mode `smc #0'
make[1]: *** [arch/arm/kernel/sysfs_v7.o] Error 1

Answer:

Your kernel tree is too old for the ELDK 5.0 tool chain.You can work around this problem by applying the following patch to your kernel tree:

   
     
     
     
     
--- arch/arm/kernel/sysfs_v7.c.ORIG   2011-01-27 11:47:54.000000000 +0100
+++ arch/arm/kernel/sysfs_v7.c   2011-05-10 08:51:58.953252638 +0200
@@ -76,7 +76,8 @@
    asm ("mrc p15, 0, %0, c1, c0, 1" : "=r"(val));
    SETBITS(val, 0xff8, new);
    val &= ~2;
-   asm ("mov r0,  %0   \n\t"
+   asm (".arch_extension sec\n\t"
+        "mov r0,  %0   \n\t"
         "mov r12, #3   \n\t"
         "smc #0      \n\t"
         :: "r"(val) : "r0", "r12");
@@ -107,7 +108,8 @@

    asm ("mrc p15, 1, %0, c9, c0, 2" : "=r"(val));
    SETBITS(val, 0xbc00000, new);
-   asm ("mov r0,  %0   \n\t"
+   asm (".arch_extension sec\n\t"
+        "mov r0,  %0   \n\t"
         "mov r12, #2   \n\t"
         "smc #0      \n\t"
         :: "r"(val) : "r0", "r12");

在代码中添加

.arch_extension sec

后，编译通过。

总结：应该是代码写法与编译器有冲突，需要在代码中声明扩展指令段