Le 14/09/2022 à 17:47, Nicholas Piggin a écrit :
> powerpc has a number of read-only sections and tables that are put
> after RO_DATA(). Move the __end_rodata symbol to cover these as well.
>
> Setting memory to read-only at boot is done using __init_begin,
> change that that to use __end_rodata.
I see the idea after looking in more details in the generated code, but
I think this commit description needs to be more explanatory.
In mm/pgtable_32.c there was a comment explaining why __init_begin is
used. I think you need to explain why we don't want to use it anymore
and why we can now use __end_rodata.
>
> This also affects boot dmesg, is_kernel_rodata(), and some other checks.
>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> ---
> arch/powerpc/kernel/vmlinux.lds.S | 3 +++
> arch/powerpc/mm/book3s32/mmu.c | 2 +-
> arch/powerpc/mm/book3s64/hash_pgtable.c | 2 +-
> arch/powerpc/mm/book3s64/radix_pgtable.c | 2 +-
> arch/powerpc/mm/pgtable_32.c | 5 ++---
> 5 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S
> b/arch/powerpc/kernel/vmlinux.lds.S
> index fe22d940412f..90ac5ff73df2 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -210,6 +210,9 @@ SECTIONS
> }
> #endif
>
> + . = ALIGN(PAGE_SIZE);
> + __end_rodata = .;
> +
I think this will likely break block mapping on PPC32.
It needs to be aligned to STRICT_ALIGN_SIZE, like __init_begin is.
> /*
> * Init sections discarded at runtime
> */
> diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
> index a96b73006dfb..e13b883e4e5b 100644
> --- a/arch/powerpc/mm/book3s32/mmu.c
> +++ b/arch/powerpc/mm/book3s32/mmu.c
> @@ -240,7 +240,7 @@ void mmu_mark_rodata_ro(void)
> for (i = 0; i < nb; i++) {
> struct ppc_bat *bat = BATS[i];
>
> - if (bat_addrs[i].start < (unsigned long)__init_begin)
> + if (bat_addrs[i].start < (unsigned long)__end_rodata)
> bat[1].batl = (bat[1].batl & ~BPP_RW) | BPP_RX;
> }
>
> diff --git a/arch/powerpc/mm/book3s64/hash_pgtable.c
> b/arch/powerpc/mm/book3s64/hash_pgtable.c
> index ae008b9df0e6..28332001bd87 100644
> --- a/arch/powerpc/mm/book3s64/hash_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/hash_pgtable.c
> @@ -541,7 +541,7 @@ void hash__mark_rodata_ro(void)
> unsigned long start, end, pp;
>
> start = (unsigned long)_stext;
> - end = (unsigned long)__init_begin;
> + end = (unsigned long)__end_rodata;
>
> pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL_ROX),
> HPTE_USE_KERNEL_KEY);
>
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c
> b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index 698274109c91..2305f34bcc33 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -228,7 +228,7 @@ void radix__mark_rodata_ro(void)
> unsigned long start, end;
>
> start = (unsigned long)_stext;
> - end = (unsigned long)__init_begin;
> + end = (unsigned long)__end_rodata;
>
> radix__change_memory_range(start, end, _PAGE_WRITE);
> }
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 3ac73f9fb5d5..112af8c5447a 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -158,10 +158,9 @@ void mark_rodata_ro(void)
> }
>
> /*
> - * mark .text and .rodata as read only. Use __init_begin rather than
> - * __end_rodata to cover NOTES and EXCEPTION_TABLE.
> + * mark .text and .rodata as read only.
> */
> - numpages = PFN_UP((unsigned long)__init_begin) -
> + numpages = PFN_UP((unsigned long)__end_rodata) -
> PFN_DOWN((unsigned long)_stext);
>
> set_memory_ro((unsigned long)_stext, numpages);
