From c4fca4fdea940bda2cff6b844cda6af8ef1c79cc Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Thu, 28 May 2015 17:46:49 +0100 Subject: [PATCH] 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 Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10205/ Signed-off-by: Ralf Baechle --- arch/mips/lib/strnlen_user.S | 15 +++++++++++++-- 1 file 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 -- 2.34.1