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| author | Maciej W. Rozycki <macro@linux-mips.org> | 2015-05-28 19:46:49 +0300 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2015-05-29 21:23:58 +0300 |
| commit | c4fca4fdea940bda2cff6b844cda6af8ef1c79cc (patch) | |
| tree | f66a7522cade4d4a883f4597b29f00dd258cdf7a /arch | |
| parent | 57b41758230b567218cb5bc3da9068aabc496fc9 (diff) | |
| download | linux-c4fca4fdea940bda2cff6b844cda6af8ef1c79cc.tar.xz | |
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')
| -rw-r--r-- | arch/mips/lib/strnlen_user.S | 15 |
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 |