diff options
| author | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-02-27 11:07:28 -0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-03-03 10:28:13 -0800 |
| commit | 52e7c52d2ded5908e6a4f8a7248e5fa6e0d6809a (patch) | |
| tree | 43ea26b8f12ba519ea77b8c83fb9cdefb46e7430 /arch/riscv/kernel/stacktrace.c | |
| parent | 064223b947a8c3d0b35a4ac9ae6e31e3f77657fd (diff) | |
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 <palmerdabbelt@google.com>
Diffstat (limited to 'arch/riscv/kernel/stacktrace.c')
| -rw-r--r-- | arch/riscv/kernel/stacktrace.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c index 0940681d2f68..02087fe539c6 100644 --- a/arch/riscv/kernel/stacktrace.c +++ b/arch/riscv/kernel/stacktrace.c @@ -19,6 +19,8 @@ struct stackframe { unsigned long ra; }; +register unsigned long sp_in_global __asm__("sp"); + void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg) { @@ -29,7 +31,7 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs, sp = user_stack_pointer(regs); pc = instruction_pointer(regs); } else if (task == NULL || task == current) { - const register unsigned long current_sp __asm__ ("sp"); + const register unsigned long current_sp = sp_in_global; fp = (unsigned long)__builtin_frame_address(0); sp = current_sp; pc = (unsigned long)walk_stackframe; @@ -73,8 +75,7 @@ static void notrace walk_stackframe(struct task_struct *task, sp = user_stack_pointer(regs); pc = instruction_pointer(regs); } else if (task == NULL || task == current) { - const register unsigned long current_sp __asm__ ("sp"); - sp = current_sp; + sp = sp_in_global; pc = (unsigned long)walk_stackframe; } else { /* task blocked in __switch_to */ |