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authorKees Cook <keescook@chromium.org>2014-04-03 22:29:50 +0200
committerKees Cook <keescook@chromium.org>2014-10-16 23:38:54 +0200
commit80d6b0c2eed2a504f6740cd1f5ea76dc50abfc4d (patch)
tree32f6d8a1c5a2250cc3f303df545dfbf52da62d19 /arch/arm/mm/init.c
parentARM: mm: allow non-text sections to be non-executable (diff)
downloadlinux-80d6b0c2eed2a504f6740cd1f5ea76dc50abfc4d.tar.xz
linux-80d6b0c2eed2a504f6740cd1f5ea76dc50abfc4d.zip
ARM: mm: allow text and rodata sections to be read-only
This introduces CONFIG_DEBUG_RODATA, making kernel text and rodata read-only. Additionally, this splits rodata from text so that rodata can also be NX, which may lead to wasted memory when aligning to SECTION_SIZE. The read-only areas are made writable during ftrace updates and kexec. Signed-off-by: Kees Cook <keescook@chromium.org> Tested-by: Laura Abbott <lauraa@codeaurora.org> Acked-by: Nicolas Pitre <nico@linaro.org>
Diffstat (limited to 'arch/arm/mm/init.c')
-rw-r--r--arch/arm/mm/init.c48
1 files changed, 47 insertions, 1 deletions
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index e6bfe76b2f59..dc2db779cdf4 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -622,9 +622,10 @@ struct section_perm {
unsigned long end;
pmdval_t mask;
pmdval_t prot;
+ pmdval_t clear;
};
-struct section_perm nx_perms[] = {
+static struct section_perm nx_perms[] = {
/* Make pages tables, etc before _stext RW (set NX). */
{
.start = PAGE_OFFSET,
@@ -639,8 +640,35 @@ struct section_perm nx_perms[] = {
.mask = ~PMD_SECT_XN,
.prot = PMD_SECT_XN,
},
+#ifdef CONFIG_DEBUG_RODATA
+ /* Make rodata NX (set RO in ro_perms below). */
+ {
+ .start = (unsigned long)__start_rodata,
+ .end = (unsigned long)__init_begin,
+ .mask = ~PMD_SECT_XN,
+ .prot = PMD_SECT_XN,
+ },
+#endif
};
+#ifdef CONFIG_DEBUG_RODATA
+static struct section_perm ro_perms[] = {
+ /* Make kernel code and rodata RX (set RO). */
+ {
+ .start = (unsigned long)_stext,
+ .end = (unsigned long)__init_begin,
+#ifdef CONFIG_ARM_LPAE
+ .mask = ~PMD_SECT_RDONLY,
+ .prot = PMD_SECT_RDONLY,
+#else
+ .mask = ~(PMD_SECT_APX | PMD_SECT_AP_WRITE),
+ .prot = PMD_SECT_APX | PMD_SECT_AP_WRITE,
+ .clear = PMD_SECT_AP_WRITE,
+#endif
+ },
+};
+#endif
+
/*
* Updates section permissions only for the current mm (sections are
* copied into each mm). During startup, this is the init_mm. Is only
@@ -704,6 +732,24 @@ static inline void fix_kernmem_perms(void)
{
set_section_perms(nx_perms, prot);
}
+
+#ifdef CONFIG_DEBUG_RODATA
+void mark_rodata_ro(void)
+{
+ set_section_perms(ro_perms, prot);
+}
+
+void set_kernel_text_rw(void)
+{
+ set_section_perms(ro_perms, clear);
+}
+
+void set_kernel_text_ro(void)
+{
+ set_section_perms(ro_perms, prot);
+}
+#endif /* CONFIG_DEBUG_RODATA */
+
#else
static inline void fix_kernmem_perms(void) { }
#endif /* CONFIG_ARM_KERNMEM_PERMS */