Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 03dce595 authored by Maciej W. Rozycki's avatar Maciej W. Rozycki Committed by Ralf Baechle
Browse files

MIPS: Fix a preemption issue with thread's FPU defaults 



Fix "BUG: using smp_processor_id() in preemptible" reported in accesses
to thread's FPU defaults: the value to initialise FSCR to at program
startup, the FCSR r/w mask and the contents of FIR in full FPU
emulation, removing a regression introduced with 9b26616c [MIPS: Respect
the ISA level in FCSR handling] and f6843626 [MIPS: math-emu: Set FIR
feature flags for full emulation].

Use `boot_cpu_data' to obtain the data from, following the approach that
`cpu_has_*' macros take and avoiding the call to `smp_processor_id' made
in the reference to `current_cpu_data'.  The contents of FSCR have to be
consistent across processors in an SMP system, the settings there must
not change as a thread is migrated across processors.  And the contents
of FIR are guaranteed to be consistent in FPU emulation, by definition.

Signed-off-by: default avatarMaciej W. Rozycki <macro@linux-mips.org>
Tested-by: default avatarEzequiel Garcia <ezequiel.garcia@imgtec.com>
Tested-by: default avatarPaul Martin <paul.martin@codethink.co.uk>
Cc: Markos Chandras <Markos.Chandras@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10030/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 620b1550

arch/mips/include/asm/elf.h

+2 −2
Original line number Diff line number Diff line
@@ -304,7 +304,7 @@ do { \ 
									\

	current->thread.abi = &mips_abi;				\

									\

	current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31;		\

	current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31;		\

} while (0)



#endif /* CONFIG_32BIT */
@@ -366,7 +366,7 @@ do { \ 
	else								\

		current->thread.abi = &mips_abi;			\

									\

	current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31;		\

	current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31;		\

									\

	p = personality(current->personality);				\

	if (p != PER_LINUX32 && p != PER_LINUX)				\

arch/mips/kernel/ptrace.c

+1 −1
Original line number Diff line number Diff line
@@ -176,7 +176,7 @@ int ptrace_setfpregs(struct task_struct *child, __u32 __user *data) 


	__get_user(value, data + 64);

	fcr31 = child->thread.fpu.fcr31;

	mask = current_cpu_data.fpu_msk31;

	mask = boot_cpu_data.fpu_msk31;

	child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask);



	/* FIR may not be written.  */

arch/mips/math-emu/cp1emu.c

+2 −2
Original line number Diff line number Diff line
@@ -889,7 +889,7 @@ static inline void cop1_cfc(struct pt_regs *xcp, struct mips_fpu_struct *ctx, 
		break;



	case FPCREG_RID:

		value = current_cpu_data.fpu_id;

		value = boot_cpu_data.fpu_id;

		break;



	default:
@@ -921,7 +921,7 @@ static inline void cop1_ctc(struct pt_regs *xcp, struct mips_fpu_struct *ctx, 
			 (void *)xcp->cp0_epc, MIPSInst_RT(ir), value);



		/* Preserve read-only bits.  */

		mask = current_cpu_data.fpu_msk31;

		mask = boot_cpu_data.fpu_msk31;

		fcr31 = (value & ~mask) | (fcr31 & mask);

		break;