Le 24/12/2019 à 06:55, Russell Currey a écrit :
The set_memory_{ro/rw/nx/x}() functions are required for STRICT_MODULE_RWX,
and are generally useful primitives to have. This implementation is
designed to be completely generic across powerpc's many MMUs.
It's possible that this could be optimised to be faster for specific
MMUs, but the focus is on having a generic and safe implementation for
now.
This implementation does not handle cases where the caller is attempting
to change the mapping of the page it is executing from, or if another
CPU is concurrently using the page being altered. These cases likely
shouldn't happen, but a more complex implementation with MMU-specific code
could safely handle them, so that is left as a TODO for now.
Signed-off-by: Russell Currey <rus...@russell.cc>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/set_memory.h | 32 +++++++++++
arch/powerpc/mm/Makefile | 1 +
arch/powerpc/mm/pageattr.c | 83 +++++++++++++++++++++++++++
4 files changed, 117 insertions(+)
create mode 100644 arch/powerpc/include/asm/set_memory.h
create mode 100644 arch/powerpc/mm/pageattr.c
+static int __change_page_attr(pte_t *ptep, unsigned long addr, void *data)
+{
+ int action = *((int *)data);
+ pte_t pte_val;
pte_val is really not a good naming, because pte_val() is already a
function which returns the value of a pte_t var.
Here you should name it 'pte' as usual.
Christophe
+
+ // invalidate the PTE so it's safe to modify
+ pte_val = ptep_get_and_clear(&init_mm, addr, ptep);
+ flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+ // modify the PTE bits as desired, then apply
+ switch (action) {
+ case SET_MEMORY_RO:
+ pte_val = pte_wrprotect(pte_val);
+ break;
+ case SET_MEMORY_RW:
+ pte_val = pte_mkwrite(pte_val);
+ break;
+ case SET_MEMORY_NX:
+ pte_val = pte_exprotect(pte_val);
+ break;
+ case SET_MEMORY_X:
+ pte_val = pte_mkexec(pte_val);
+ break;
+ default:
+ WARN_ON(true);
+ return -EINVAL;
+ }
+
+ set_pte_at(&init_mm, addr, ptep, pte_val);
+
+ return 0;
+}
+
