Re: [PATCH 2/7] powerpc: move __end_rodata to cover arch read-only sections
From: Christophe Leroy <hidden>
Date: 2022-09-15 05:51:49
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.
quoted hunk ↗ jump to hunk
This also affects boot dmesg, is_kernel_rodata(), and some other checks. Signed-off-by: Nicholas Piggin <npiggin@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.
quoted hunk ↗ jump to hunk
/* * 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);