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authorMaciej W. Rozycki <macro@linux-mips.org>2015-05-28 17:46:49 +0100
committerRalf Baechle <ralf@linux-mips.org>2015-05-29 20:23:58 +0200
commitc4fca4fdea940bda2cff6b844cda6af8ef1c79cc (patch)
treef66a7522cade4d4a883f4597b29f00dd258cdf7a /arch/mips/lib
parent57b41758230b567218cb5bc3da9068aabc496fc9 (diff)
MIPS: strnlen_user.S: Fix a CPU_DADDI_WORKAROUNDS regression
Correct a regression introduced with 8453eebd [MIPS: Fix strnlen_user() return value in case of overlong strings.] causing assembler warnings and broken code generated in __strnlen_kernel_nocheck_asm: arch/mips/lib/strnlen_user.S: Assembler messages: arch/mips/lib/strnlen_user.S:64: Warning: Macro instruction expanded into multiple instructions in a branch delay slot with the CPU_DADDI_WORKAROUNDS option set, resulting in the function looping indefinitely upon mounting NFS root. Use conditional assembly to avoid a microMIPS code size regression. Using $at unconditionally would cause such a regression as there are no 16-bit instruction encodings available for ALU operations using this register. Using $v1 unconditionally would produce short microMIPS encodings, but would prevent this register from being used across calls to this function. The extra LI operation introduced is free, replacing a NOP originally scheduled into the delay slot of the branch that follows. Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10205/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/lib')
-rw-r--r--arch/mips/lib/strnlen_user.S15
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/mips/lib/strnlen_user.S b/arch/mips/lib/strnlen_user.S
index 7d12c0dded3d..77e64942f004 100644
--- a/arch/mips/lib/strnlen_user.S
+++ b/arch/mips/lib/strnlen_user.S
@@ -34,7 +34,12 @@ LEAF(__strnlen_\func\()_asm)
FEXPORT(__strnlen_\func\()_nocheck_asm)
move v0, a0
PTR_ADDU a1, a0 # stop pointer
-1: beq v0, a1, 1f # limit reached?
+1:
+#ifdef CONFIG_CPU_DADDI_WORKAROUNDS
+ .set noat
+ li AT, 1
+#endif
+ beq v0, a1, 1f # limit reached?
.ifeqs "\func", "kernel"
EX(lb, t0, (v0), .Lfault\@)
.else
@@ -42,7 +47,13 @@ FEXPORT(__strnlen_\func\()_nocheck_asm)
.endif
.set noreorder
bnez t0, 1b
-1: PTR_ADDIU v0, 1
+1:
+#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
+ PTR_ADDIU v0, 1
+#else
+ PTR_ADDU v0, AT
+ .set at
+#endif
.set reorder
PTR_SUBU v0, a0
jr ra