I am about to commit: http://sourceware.org/ml/binutils/2010-10/msg00033.html that fixes a problem with the LD/SD macro currently implemented by GAS for the o32 ABI in an inconsistent way. This is best illustrated with a simple program, which I'm copying here from the message above for easier reference: $ cat ld.s ld $5,32767($4) ld $5,32768($4) This gets assebled into the following output: $ mips-linux-as -32 -mips3 -o ld.o ld.s $ mips-linux-objdump -d ld.o ld.o: file format elf32-tradbigmips Disassembly of section .text: 00000000 <.text>: 0: dc857fff ld a1,32767(a0) 4: 3c010001 lui at,0x1 8: 00810821 addu at,a0,at c: 8c258000 lw a1,-32768(at) 10: 8c268004 lw a2,-32764(at) ... Oops! The GAS fix makes the macro behave in a consistent way and pairs of LW/SW instructions to be output as appropriate regardless of the size of the offset associated with the address used. The machine instruction is still available, but to reach it macros have to be disabled first. This has a side effect of requiring the use of a machine-addressable memory operand. As some platforms require 64-bit operations for accesses to some I/O registers LD/SD instructions are used in a couple of places in Linux regardless of the ABI selected. Here's a fix for some pieces of code affected I've been able to track down. The fix should be backwards compatible with all supported binutils releases in existence and can be used as a reference for any other places or off-tree code. The use of the "R" constraint guarantees a machine-addressable operand. Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> --- Ralf: please apply, including any relevand maintenance branches. Note I have not tested this change; I have no resources to do so at the moment, sorry. Platform maintainers: please audit your code for any other places that may require such a change. Note only LD/SD macros are affected, other 64-bit intructions are fine, including LLD/SCD that are not macros on o32 (barring any complex address calculations required for modes not directly supported by hardware). Maciej patch-mips-2.6.36-rc4-20101010-ldsd-nomacro-0 diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index c98bf51..5b017f2 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -329,10 +329,14 @@ static inline void pfx##write##bwlq(type val, \ "dsrl32 %L0, %L0, 0" "\n\t" \ "dsll32 %M0, %M0, 0" "\n\t" \ "or %L0, %L0, %M0" "\n\t" \ + ".set push" "\n\t" \ + ".set noreorder" "\n\t" \ + ".set nomacro" "\n\t" \ "sd %L0, %2" "\n\t" \ + ".set pop" "\n\t" \ ".set mips0" "\n" \ : "=r" (__tmp) \ - : "0" (__val), "m" (*__mem)); \ + : "0" (__val), "R" (*__mem)); \ if (irq) \ local_irq_restore(__flags); \ } else \ @@ -355,12 +359,16 @@ static inline type pfx##read##bwlq(const volatile void __iomem *mem) \ local_irq_save(__flags); \ __asm__ __volatile__( \ ".set mips3" "\t\t# __readq" "\n\t" \ + ".set push" "\n\t" \ + ".set noreorder" "\n\t" \ + ".set nomacro" "\n\t" \ "ld %L0, %1" "\n\t" \ + ".set pop" "\n\t" \ "dsra32 %M0, %L0, 0" "\n\t" \ "sll %L0, %L0, 0" "\n\t" \ ".set mips0" "\n" \ : "=r" (__val) \ - : "m" (*__mem)); \ + : "R" (*__mem)); \ if (irq) \ local_irq_restore(__flags); \ } else { \ diff --git a/arch/mips/pmc-sierra/yosemite/py-console.c b/arch/mips/pmc-sierra/yosemite/py-console.c index b7f1d9c..434d7b1 100644 --- a/arch/mips/pmc-sierra/yosemite/py-console.c +++ b/arch/mips/pmc-sierra/yosemite/py-console.c @@ -65,11 +65,15 @@ static unsigned char readb_outer_space(unsigned long long phys) __asm__ __volatile__ ( " .set mips3 \n" + " .set push \n" + " .set noreorder \n" + " .set nomacro \n" " ld %0, %1 \n" + " .set pop \n" " lbu %0, (%0) \n" " .set mips0 \n" : "=r" (res) - : "m" (vaddr)); + : "R" (vaddr)); write_c0_status(sr); ssnop_4(); @@ -89,11 +93,15 @@ static void writeb_outer_space(unsigned long long phys, unsigned char c) __asm__ __volatile__ ( " .set mips3 \n" + " .set push \n" + " .set noreorder \n" + " .set nomacro \n" " ld %0, %1 \n" + " .set pop \n" " sb %2, (%0) \n" " .set mips0 \n" : "=&r" (tmp) - : "m" (vaddr), "r" (c)); + : "R" (vaddr), "r" (c)); write_c0_status(sr); ssnop_4();
