From 52e7c52d2ded5908e6a4f8a7248e5fa6e0d6809a Mon Sep 17 00:00:00 2001 From: Palmer Dabbelt Date: Thu, 27 Feb 2020 11:07:28 -0800 Subject: RISC-V: Stop relying on GCC's register allocator's hueristics GCC allows users to hint to the register allocation that a variable should be placed in a register by using a syntax along the lines of function(...) { register long in_REG __asm__("REG"); } We've abused this a bit throughout the RISC-V port to access fixed registers directly as C variables. In practice it's never going to blow up because GCC isn't going to allocate these registers, but it's not a well defined syntax so we really shouldn't be relying upon this. Luckily there is a very similar but well defined syntax that allows us to still access these registers directly as C variables, which is to simply declare the register variables globally. For fixed variables this doesn't change the ABI. LLVM disallows this ambiguous syntax, so this isn't just strictly a formatting change. Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/process.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'arch/riscv/kernel/process.c') diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 817cf7b0974c..610c11e91606 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -22,6 +22,8 @@ #include #include +unsigned long gp_in_global __asm__("gp"); + extern asmlinkage void ret_from_fork(void); extern asmlinkage void ret_from_kernel_thread(void); @@ -107,9 +109,8 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp, /* p->thread holds context to be restored by __switch_to() */ if (unlikely(p->flags & PF_KTHREAD)) { /* Kernel thread */ - const register unsigned long gp __asm__ ("gp"); memset(childregs, 0, sizeof(struct pt_regs)); - childregs->gp = gp; + childregs->gp = gp_in_global; /* Supervisor/Machine, irqs on: */ childregs->status = SR_PP | SR_PIE; -- cgit v1.2.3