diff options
| author | Palmer Dabbelt <palmer@rivosinc.com> | 2022-12-12 09:30:37 -0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-12-12 09:30:37 -0800 |
| commit | c3ec1e8964fb0ca00c79936160a027bd8b47e140 (patch) | |
| tree | a9391a50f9c9205a87244dbfae6519b7774bddb6 /arch/riscv/kernel/traps.c | |
| parent | d01404fa7b8c72c7052232423f30a16060828f28 (diff) | |
| parent | de57ecc476103179e93fd85091770921f76a19af (diff) | |
Merge patch series "RISC-V: Align the shadow stack"
Palmer Dabbelt <palmer@rivosinc.com> says:
This contains a pair of cleanups that depend on a fix that has already
landed upstream.
* b4-shazam-merge:
RISC-V: Add some comments about the shadow and overflow stacks
RISC-V: Align the shadow stack
riscv: fix race when vmap stack overflow
Link: https://lore.kernel.org/r/20221130023515.20217-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/kernel/traps.c')
| -rw-r--r-- | arch/riscv/kernel/traps.c | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f3e96d60a2ff..549bde5c970a 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -208,13 +208,28 @@ int is_valid_bugaddr(unsigned long pc) #endif /* CONFIG_GENERIC_BUG */ #ifdef CONFIG_VMAP_STACK +/* + * Extra stack space that allows us to provide panic messages when the kernel + * has overflowed its stack. + */ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)__aligned(16); /* - * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used - * to get per-cpu overflow stack(get_overflow_stack). + * A temporary stack for use by handle_kernel_stack_overflow. This is used so + * we can call into C code to get the per-hart overflow stack. Usage of this + * stack must be protected by spin_shadow_stack. */ -long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)]; +long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); + +/* + * A pseudo spinlock to protect the shadow stack from being used by multiple + * harts concurrently. This isn't a real spinlock because the lock side must + * be taken without a valid stack and only a single register, it's only taken + * while in the process of panicing anyway so the performance and error + * checking a proper spinlock gives us doesn't matter. + */ +unsigned long spin_shadow_stack; + asmlinkage unsigned long get_overflow_stack(void) { return (unsigned long)this_cpu_ptr(overflow_stack) + @@ -226,6 +241,15 @@ asmlinkage void handle_bad_stack(struct pt_regs *regs) unsigned long tsk_stk = (unsigned long)current->stack; unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack); + /* + * We're done with the shadow stack by this point, as we're on the + * overflow stack. Tell any other concurrent overflowing harts that + * they can proceed with panicing by releasing the pseudo-spinlock. + * + * This pairs with an amoswap.aq in handle_kernel_stack_overflow. + */ + smp_store_release(&spin_shadow_stack, 0); + console_verbose(); pr_emerg("Insufficient stack space to handle exception!\n"); |