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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-03-09 21:52:02 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2017-03-23 13:54:33 +0000
commit28b066da69b937ea4104341cb5d9324109faab7f (patch)
treefd756df58f4a49ff370059200cd7a920dbe04e55 /arch/arm64
parent5ea5306c3235a157f06040c59730b1133115ed26 (diff)
downloadop-kernel-dev-28b066da69b937ea4104341cb5d9324109faab7f.zip
op-kernel-dev-28b066da69b937ea4104341cb5d9324109faab7f.tar.gz
arm64: mmu: map .text as read-only from the outset
Now that alternatives patching code no longer relies on the primary mapping of .text being writable, we can remove the code that removes the writable permissions post-init time, and map it read-only from the outset. To preserve the existing behavior under rodata=off, which is relied upon by external debuggers to manage software breakpoints (as pointed out by Mark), add an early_param() check for rodata=, and use RWX permissions if it set to 'off'. Reviewed-by: Laura Abbott <labbott@redhat.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/mm/mmu.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index df377fb..300e98e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -416,9 +416,6 @@ void mark_rodata_ro(void)
{
unsigned long section_size;
- section_size = (unsigned long)_etext - (unsigned long)_text;
- update_mapping_prot(__pa_symbol(_text), (unsigned long)_text,
- section_size, PAGE_KERNEL_ROX);
/*
* mark .rodata as read only. Use __init_begin rather than __end_rodata
* to cover NOTES and EXCEPTION_TABLE.
@@ -451,6 +448,12 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
vm_area_add_early(vma);
}
+static int __init parse_rodata(char *arg)
+{
+ return strtobool(arg, &rodata_enabled);
+}
+early_param("rodata", parse_rodata);
+
/*
* Create fine-grained mappings for the kernel.
*/
@@ -458,7 +461,14 @@ static void __init map_kernel(pgd_t *pgd)
{
static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_init, vmlinux_data;
- map_kernel_segment(pgd, _text, _etext, PAGE_KERNEL_EXEC, &vmlinux_text);
+ /*
+ * External debuggers may need to write directly to the text
+ * mapping to install SW breakpoints. Allow this (only) when
+ * explicitly requested with rodata=off.
+ */
+ pgprot_t text_prot = rodata_enabled ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;
+
+ map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text);
map_kernel_segment(pgd, __start_rodata, __init_begin, PAGE_KERNEL, &vmlinux_rodata);
map_kernel_segment(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC,
&vmlinux_init);
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