Starting with version 2.24.51.20140728 MIPS binutils complain loudly
about mixing soft-float and hard-float object files, leading to this
build failure since GCC is invoked with "-msoft-float" on MIPS:
{standard input}: Warning: .gnu_attribute 4,3 requires `softfloat'
LD arch/mips/alchemy/common/built-in.o
mipsel-softfloat-linux-gnu-ld: Warning: arch/mips/alchemy/common/built-in.o
uses -msoft-float (set by arch/mips/alchemy/common/prom.o),
arch/mips/alchemy/common/sleeper.o uses -mhard-float
To fix this, we detect if GAS is new enough to support "-msoft-float" command
option, and if it does, we can let GCC pass it to GAS; but then we also need
to sprinkle the files which make use of floating point registers with the
necessary ".set hardfloat" directives.
Signed-off-by: Manuel Lauss <manuel.lauss@xxxxxxxxx>
---
I've only tested a mips32r1 build, but at least binutils-2.23 and a
snapshot from today (with the MIPS fp changes) compile a bootable
kernel.
Tests on 64bit and with MSA and other extensions also appreciated!
v3: incorporate Maciej's suggestions:
- detect if gas can handle -msoft-float and ".set hardfloat"
- apply .set hardfloat only where really necessary
v2: cover more files
This was introduced in binutils commit 351cdf24d223290b15fa991e5052ec9e9bd1e284
("[MIPS] Implement O32 FPXX, FP64 and FP64A ABI extensions").
arch/mips/Makefile | 9 +++++++++
arch/mips/include/asm/asmmacro-32.h | 5 +++++
arch/mips/include/asm/asmmacro.h | 18 ++++++++++++++++++
arch/mips/include/asm/fpregdef.h | 14 ++++++++++++++
arch/mips/include/asm/mipsregs.h | 19 +++++++++++++++++++
arch/mips/kernel/genex.S | 1 +
arch/mips/kernel/r2300_switch.S | 5 +++++
arch/mips/kernel/r4k_fpu.S | 7 +++++++
arch/mips/kernel/r4k_switch.S | 9 +++++++++
arch/mips/kernel/r6000_fpu.S | 5 +++++
10 files changed, 92 insertions(+)
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index bbac51e1..35005e1 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -93,6 +93,15 @@ LDFLAGS_vmlinux += -G 0 -static -n -nostdlib
KBUILD_AFLAGS_MODULE += -mlong-calls
KBUILD_CFLAGS_MODULE += -mlong-calls
+#
+# pass -msoft-float to GAS if it supports it. However on newer binutils
+# (specifically newer than 2.24.51.20140728) we then also need to explicitly
+# set ".set hardfloat" in all files which manipulate floating point registers.
+#
+ifneq ($(call as-option,-Wa$(comma)-msoft-float,),)
+ cflags-y += -DGAS_HAS_SET_HARDFLOAT -Wa,-msoft-float
+endif
+
cflags-y += -ffreestanding
#
diff --git a/arch/mips/include/asm/asmmacro-32.h b/arch/mips/include/asm/asmmacro-32.h
index e38c281..a97ce53 100644
--- a/arch/mips/include/asm/asmmacro-32.h
+++ b/arch/mips/include/asm/asmmacro-32.h
@@ -12,6 +12,9 @@
#include <asm/fpregdef.h>
#include <asm/mipsregs.h>
+ .set push
+ SET_HARDFLOAT
+
.macro fpu_save_single thread tmp=t0
cfc1 \tmp, fcr31
swc1 $f0, THREAD_FPR0_LS64(\thread)
@@ -86,6 +89,8 @@
ctc1 \tmp, fcr31
.endm
+ .set pop
+
.macro cpu_save_nonscratch thread
LONG_S s0, THREAD_REG16(\thread)
LONG_S s1, THREAD_REG17(\thread)
diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
index cd9a98b..6caf876 100644
--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -57,6 +57,8 @@
#endif /* CONFIG_CPU_MIPSR2 */
.macro fpu_save_16even thread tmp=t0
+ .set push
+ SET_HARDFLOAT
cfc1 \tmp, fcr31
sdc1 $f0, THREAD_FPR0_LS64(\thread)
sdc1 $f2, THREAD_FPR2_LS64(\thread)
@@ -75,11 +77,13 @@
sdc1 $f28, THREAD_FPR28_LS64(\thread)
sdc1 $f30, THREAD_FPR30_LS64(\thread)
sw \tmp, THREAD_FCR31(\thread)
+ .set pop
.endm
.macro fpu_save_16odd thread
.set push
.set mips64r2
+ SET_HARDFLOAT
sdc1 $f1, THREAD_FPR1_LS64(\thread)
sdc1 $f3, THREAD_FPR3_LS64(\thread)
sdc1 $f5, THREAD_FPR5_LS64(\thread)
@@ -110,6 +114,8 @@
.endm
.macro fpu_restore_16even thread tmp=t0
+ .set push
+ SET_HARDFLOAT
lw \tmp, THREAD_FCR31(\thread)
ldc1 $f0, THREAD_FPR0_LS64(\thread)
ldc1 $f2, THREAD_FPR2_LS64(\thread)
@@ -133,6 +139,7 @@
.macro fpu_restore_16odd thread
.set push
.set mips64r2
+ SET_HARDFLOAT
ldc1 $f1, THREAD_FPR1_LS64(\thread)
ldc1 $f3, THREAD_FPR3_LS64(\thread)
ldc1 $f5, THREAD_FPR5_LS64(\thread)
@@ -277,6 +284,7 @@
.macro cfcmsa rd, cs
.set push
.set noat
+ SET_HARDFLOAT
.insn
.word CFC_MSA_INSN | (\cs << 11)
move \rd, $1
@@ -286,6 +294,7 @@
.macro ctcmsa cd, rs
.set push
.set noat
+ SET_HARDFLOAT
move $1, \rs
.word CTC_MSA_INSN | (\cd << 6)
.set pop
@@ -294,6 +303,7 @@
.macro ld_d wd, off, base
.set push
.set noat
+ SET_HARDFLOAT
add $1, \base, \off
.word LDD_MSA_INSN | (\wd << 6)
.set pop
@@ -302,6 +312,7 @@
.macro st_d wd, off, base
.set push
.set noat
+ SET_HARDFLOAT
add $1, \base, \off
.word STD_MSA_INSN | (\wd << 6)
.set pop
@@ -310,6 +321,7 @@
.macro copy_u_w rd, ws, n
.set push
.set noat
+ SET_HARDFLOAT
.insn
.word COPY_UW_MSA_INSN | (\n << 16) | (\ws << 11)
/* move triggers an assembler bug... */
@@ -320,6 +332,7 @@
.macro copy_u_d rd, ws, n
.set push
.set noat
+ SET_HARDFLOAT
.insn
.word COPY_UD_MSA_INSN | (\n << 16) | (\ws << 11)
/* move triggers an assembler bug... */
@@ -330,6 +343,7 @@
.macro insert_w wd, n, rs
.set push
.set noat
+ SET_HARDFLOAT
/* move triggers an assembler bug... */
or $1, \rs, zero
.word INSERT_W_MSA_INSN | (\n << 16) | (\wd << 6)
@@ -339,6 +353,7 @@
.macro insert_d wd, n, rs
.set push
.set noat
+ SET_HARDFLOAT
/* move triggers an assembler bug... */
or $1, \rs, zero
.word INSERT_D_MSA_INSN | (\n << 16) | (\wd << 6)
@@ -381,6 +396,7 @@
st_d 31, THREAD_FPR31, \thread
.set push
.set noat
+ SET_HARDFLOAT
cfcmsa $1, MSA_CSR
sw $1, THREAD_MSA_CSR(\thread)
.set pop
@@ -389,6 +405,7 @@
.macro msa_restore_all thread
.set push
.set noat
+ SET_HARDFLOAT
lw $1, THREAD_MSA_CSR(\thread)
ctcmsa MSA_CSR, $1
.set pop
@@ -441,6 +458,7 @@
.macro msa_init_all_upper
.set push
.set noat
+ SET_HARDFLOAT
not $1, zero
msa_init_upper 0
.set pop
diff --git a/arch/mips/include/asm/fpregdef.h b/arch/mips/include/asm/fpregdef.h
index 429481f..f184ba0 100644
--- a/arch/mips/include/asm/fpregdef.h
+++ b/arch/mips/include/asm/fpregdef.h
@@ -14,6 +14,20 @@
#include <asm/sgidefs.h>
+/*
+ * starting with binutils 2.24.51.20140729, MIPS binutils warn about mixing
+ * hardfloat and softfloat object files. The kernel build uses soft-float by
+ * default, so we also need to pass -msoft-float along to GAS if it supports it.
+ * But this in turn causes assembler errors in files which access hardfloat
+ * registers. We detect if GAS supports "-msoft-float" in the Makefile and
+ * explicitly put ".set hardfloat" where floating point registers are touched.
+ */
+#ifdef GAS_HAS_SET_HARDFLOAT
+#define SET_HARDFLOAT .set hardfloat
+#else
+#define SET_HARDFLOAT
+#endif
+
#if _MIPS_SIM == _MIPS_SIM_ABI32
/*
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index cf3b580..889c012 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -1324,6 +1324,7 @@ do { \
/*
* Macros to access the floating point coprocessor control registers
*/
+#ifdef GAS_HAS_SET_HARDFLOAT
#define read_32bit_cp1_register(source) \
({ \
int __res; \
@@ -1334,11 +1335,29 @@ do { \
" # gas fails to assemble cfc1 for some archs, \n" \
" # like Octeon. \n" \
" .set mips1 \n" \
+ " .set hardfloat \n" \
" cfc1 %0,"STR(source)" \n" \
" .set pop \n" \
: "=r" (__res)); \
__res; \
})
+#else
+#define read_32bit_cp1_register(source) \
+({ \
+ int __res; \
+ \
+ __asm__ __volatile__( \
+ " .set push \n" \
+ " .set reorder \n" \
+ " # gas fails to assemble cfc1 for some archs, \n" \
+ " # like Octeon. \n" \
+ " .set mips1 \n" \
+ " cfc1 %0,"STR(source)" \n" \
+ " .set pop \n" \
+ : "=r" (__res)); \
+ __res; \
+})
+#endif
#ifdef HAVE_AS_DSP
#define rddsp(mask) \
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index ac35e12..a5e26dd 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -358,6 +358,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
.set push
/* gas fails to assemble cfc1 for some archs (octeon).*/ \
.set mips1
+ SET_HARDFLOAT
cfc1 a1, fcr31
li a2, ~(0x3f << 12)
and a2, a1
diff --git a/arch/mips/kernel/r2300_switch.S b/arch/mips/kernel/r2300_switch.S
index 20b7b04..435ea65 100644
--- a/arch/mips/kernel/r2300_switch.S
+++ b/arch/mips/kernel/r2300_switch.S
@@ -120,6 +120,9 @@ LEAF(_restore_fp)
#define FPU_DEFAULT 0x00000000
+ .set push
+ SET_HARDFLOAT
+
LEAF(_init_fpu)
mfc0 t0, CP0_STATUS
li t1, ST0_CU1
@@ -165,3 +168,5 @@ LEAF(_init_fpu)
mtc1 t0, $f31
jr ra
END(_init_fpu)
+
+ .set pop
diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 8352523..4a827a3 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -21,6 +21,7 @@
.macro EX insn, reg, src
.set push
+ SET_HARDFLOAT
.set nomacro
.ex\@: \insn \reg, \src
.set pop
@@ -33,7 +34,10 @@
.set arch=r4000
LEAF(_save_fp_context)
+ .set push
+ SET_HARDFLOAT
cfc1 t1, fcr31
+ .set pop
#if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPS32_R2)
.set push
@@ -191,7 +195,10 @@ LEAF(_restore_fp_context)
EX ldc1 $f26, SC_FPREGS+208(a0)
EX ldc1 $f28, SC_FPREGS+224(a0)
EX ldc1 $f30, SC_FPREGS+240(a0)
+ .set push
+ SET_HARDFLOAT
ctc1 t1, fcr31
+ .set pop
jr ra
li v0, 0 # success
END(_restore_fp_context)
diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S
index 4c4ec18..6467a8b 100644
--- a/arch/mips/kernel/r4k_switch.S
+++ b/arch/mips/kernel/r4k_switch.S
@@ -65,8 +65,12 @@
bgtz a3, 1f
/* Save 128b MSA vector context + scalar FP control & status. */
+ .set push
+ SET_HARDFLOAT
cfc1 t1, fcr31
msa_save_all a0
+ .set pop /* SET_HARDFLOAT */
+
sw t1, THREAD_FCR31(a0)
b 2f
@@ -161,6 +165,9 @@ LEAF(_init_msa_upper)
#define FPU_DEFAULT 0x00000000
+ .set push
+ SET_HARDFLOAT
+
LEAF(_init_fpu)
mfc0 t0, CP0_STATUS
li t1, ST0_CU1
@@ -291,3 +298,5 @@ LEAF(_init_fpu)
#endif
jr ra
END(_init_fpu)
+
+ .set pop /* SET_HARDFLOAT */
diff --git a/arch/mips/kernel/r6000_fpu.S b/arch/mips/kernel/r6000_fpu.S
index da0fbe4..4707738 100644
--- a/arch/mips/kernel/r6000_fpu.S
+++ b/arch/mips/kernel/r6000_fpu.S
@@ -18,6 +18,9 @@
.set noreorder
.set mips2
+ .set push
+ SET_HARDFLOAT
+
/* Save floating point context */
LEAF(_save_fp_context)
mfc0 t0,CP0_STATUS
@@ -85,3 +88,5 @@
1: jr ra
nop
END(_restore_fp_context)
+
+ .set pop /* SET_HARDFLOAT */
--
2.1.2
