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[Patch] New option to enable linux kernel builds

[There is no current Xtensa maintainer, although I am again working to become such. Would someone review and apply this patch please?]


On Xtensa, user-land code must be compiled PIC, and thus the current port ignores the -fno-pic flag, which enables most packages to compile successfully without a problem.

However, under some fairly unusual circumstances, certain bits of software--such as parts of the Linux kernel--really do need to be built without PIC. The attached patch introduces a new Xtensa option "-mforce-no-pic" to allow this.



diff -urd gcc-4.3.3.orig/gcc/config/xtensa/xtensa.c gcc-4.3.3/gcc/config/xtensa/xtensa.c
--- gcc-4.3.3.orig/gcc/config/xtensa/xtensa.c	2008-01-11 14:44:47.000000000 -0800
+++ gcc-4.3.3/gcc/config/xtensa/xtensa.c	2010-01-10 07:59:07.000000000 -0800
@@ -1899,6 +1899,8 @@
   if (flag_pic && TARGET_CONST16)
     error ("-f%s is not supported with CONST16 instructions",
 	   (flag_pic > 1 ? "PIC" : "pic"));
+  else if (TARGET_FORCE_NO_PIC)
+    flag_pic = 0;
   else if (XTENSA_ALWAYS_PIC)
       if (TARGET_CONST16)
diff -urd gcc-4.3.3.orig/gcc/config/xtensa/xtensa.opt gcc-4.3.3/gcc/config/xtensa/xtensa.opt
--- gcc-4.3.3.orig/gcc/config/xtensa/xtensa.opt	2007-08-02 03:49:31.000000000 -0700
+++ gcc-4.3.3/gcc/config/xtensa/xtensa.opt	2010-01-10 07:59:07.000000000 -0800
@@ -26,6 +26,10 @@
 Target Report Mask(FUSED_MADD)
 Enable fused multiply/add and multiply/subtract FP instructions
+Target Report Mask(FORCE_NO_PIC)
+Disable position-independent code (PIC) for use in OS kernel code
 Use indirect CALLXn instructions for large programs
diff -urd gcc-4.3.3.orig/gcc/doc/invoke.texi gcc-4.3.3/gcc/doc/invoke.texi
--- gcc-4.3.3.orig/gcc/doc/invoke.texi	2008-11-21 08:21:50.000000000 -0800
+++ gcc-4.3.3/gcc/doc/invoke.texi	2010-01-10 07:59:07.000000000 -0800
@@ -798,6 +798,7 @@
 @emph{Xtensa Options}
 @gccoptlist{-mconst16 -mno-const16 @gol
 -mfused-madd  -mno-fused-madd @gol
+-mforce-no-pic @gol
 -mtext-section-literals  -mno-text-section-literals @gol
 -mtarget-align  -mno-target-align @gol
 -mlongcalls  -mno-longcalls}
@@ -14723,6 +14724,12 @@
 sensitive to the compiler's ability to combine multiply and add/subtract
+@item -mforce-no-pic
+@opindex mforce-no-pic
+For targets, like GNU/Linux, where all user-mode Xtensa code must be
+position-independent code (PIC), this option disables PIC for compiling
+kernel code.
 @item -mtext-section-literals
 @itemx -mno-text-section-literals
 @opindex mtext-section-literals

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