2020-05-31 10:02:52

by Anup Patel

Subject: [PATCH] RISC-V: Don't mark init section as non-executable

The head text section (i.e. _start, secondary_start_sbi, etc) and the
init section fall under same page table level-1 mapping.

Currently, the runtime CPU hotplug is broken because we are marking
init section as non-executable which in-turn marks head text section
as non-executable.

Further investigating other architectures, it seems marking the init
section as non-executable is redundant because the init section pages
are anyway poisoned and freed.

To fix broken runtime CPU hotplug, we simply remove the code marking
the init section as non-executable.

Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
Cc: [email protected]
Signed-off-by: Anup Patel <[email protected]>
---
arch/riscv/mm/init.c | 5 -----
1 file changed, 5 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 736de6c8739f..e0f8ccab8a41 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -482,11 +482,6 @@ static void __init setup_vm_final(void)

void free_initmem(void)
{
- unsigned long init_begin = (unsigned long)__init_begin;
- unsigned long init_end = (unsigned long)__init_end;
-
- /* Make the region as non-execuatble. */
- set_memory_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
free_initmem_default(POISON_FREE_INITMEM);
}

--
2.25.1

2020-06-01 04:22:37

by Anup Patel

Subject: Re: [PATCH] RISC-V: Don't mark init section as non-executable

On Sun, May 31, 2020 at 3:28 PM Anup Patel <[email protected]> wrote:
>
> The head text section (i.e. _start, secondary_start_sbi, etc) and the
> init section fall under same page table level-1 mapping.
>
> Currently, the runtime CPU hotplug is broken because we are marking
> init section as non-executable which in-turn marks head text section
> as non-executable.
>
> Further investigating other architectures, it seems marking the init
> section as non-executable is redundant because the init section pages
> are anyway poisoned and freed.
>
> To fix broken runtime CPU hotplug, we simply remove the code marking
> the init section as non-executable.
>
> Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
> Cc: [email protected]
> Signed-off-by: Anup Patel <[email protected]>
> ---
> arch/riscv/mm/init.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 736de6c8739f..e0f8ccab8a41 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -482,11 +482,6 @@ static void __init setup_vm_final(void)
>
> void free_initmem(void)
> {
> - unsigned long init_begin = (unsigned long)__init_begin;
> - unsigned long init_end = (unsigned long)__init_end;
> -
> - /* Make the region as non-execuatble. */
> - set_memory_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
> free_initmem_default(POISON_FREE_INITMEM);
> }

I just realized that updated free_initmem() over here is exactly
same as generic free_initmem() defined in init/main.c so it's better
to remove free_initmem() from here. I will send v2.

Regards,
Anup