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powerpc/vmlinux.lds: Add an explicit symbol for the SRWX boundary

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Currently __init_begin is used as the boundary for strict RWX between
executable/read-only text and data, and non-executable (after boot) code
and data.

But that's a little subtle, so add an explicit symbol to document that
the SRWX boundary lies there, and add a comment making it clear that
__init_begin must also begin there.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220916131422.318752-2-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2022-09-16 14:41:24 +10:00
parent 331771e836
commit b150a4d12b
4 changed files with 11 additions and 5 deletions
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1
arch/powerpc/include/asm/sections.h
View file

@ -13,6 +13,7 @@ typedef struct func_desc func_desc_t;
#include <asm-generic/sections.h>
extern char __head_end[];
extern char __srwx_boundary[];
/* Patch sites */
extern s32 patch__call_flush_branch_caches1;

9
arch/powerpc/kernel/vmlinux.lds.S
View file

@ -214,11 +214,16 @@ SECTIONS
}
#endif
/*
* Various code relies on __init_begin being at the strict RWX boundary.
*/
. = ALIGN(STRICT_ALIGN_SIZE);
__srwx_boundary = .;
__init_begin = .;
/*
* Init sections discarded at runtime
*/
. = ALIGN(STRICT_ALIGN_SIZE);
__init_begin = .;
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
_sinittext = .;
INIT_TEXT

2
arch/powerpc/mm/book3s32/mmu.c
View file

@ -158,7 +158,7 @@ static unsigned long __init __mmu_mapin_ram(unsigned long base, unsigned long to
unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
{
unsigned long done;
unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
unsigned long border = (unsigned long)__srwx_boundary - PAGE_OFFSET;
unsigned long size;
size = roundup_pow_of_two((unsigned long)_einittext - PAGE_OFFSET);

4
arch/powerpc/mm/book3s64/radix_pgtable.c
View file

@ -259,8 +259,8 @@ print_mapping(unsigned long start, unsigned long end, unsigned long size, bool e
static unsigned long next_boundary(unsigned long addr, unsigned long end)
{
#ifdef CONFIG_STRICT_KERNEL_RWX
if (addr < __pa_symbol(__init_begin))
return __pa_symbol(__init_begin);
if (addr < __pa_symbol(__srwx_boundary))
return __pa_symbol(__srwx_boundary);
#endif
return end;
}