Le 25/05/2017 à 05:36, Balbir Singh a écrit :
Today our patching happens via direct copy and
patch_instruction. The patching code is well
contained in the sense that copying bits are limited.
While considering implementation of CONFIG_STRICT_RWX,
the first requirement is to a create another mapping
that will allow for patching. We create the window using
text_poke_area, allocated via get_vm_area(), which might
be an overkill. We can do per-cpu stuff as well. The
downside of these patches that patch_instruction is
now synchornized using a lock. Other arches do similar
things, but use fixmaps. The reason for not using
fixmaps is to make use of any randomization in the
future. The code also relies on set_pte_at and pte_clear
to do the appropriate tlb flushing.
Signed-off-by: Balbir Singh <bsinghar...@gmail.com>
---
arch/powerpc/lib/code-patching.c | 88 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 84 insertions(+), 4 deletions(-)
[...]
+static int kernel_map_addr(void *addr)
+{
+ unsigned long pfn;
int err;
- __put_user_size(instr, addr, 4, err);
+ if (is_vmalloc_addr(addr))
+ pfn = vmalloc_to_pfn(addr);
+ else
+ pfn = __pa_symbol(addr) >> PAGE_SHIFT;
+
+ err = map_kernel_page((unsigned long)text_poke_area->addr,
+ (pfn << PAGE_SHIFT), _PAGE_KERNEL_RW | _PAGE_PRESENT);
Why not use PAGE_KERNEL instead of _PAGE_KERNEL_RW | _PAGE_PRESENT ?
From asm/pte-common.h :
#define PAGE_KERNEL __pgprot(_PAGE_BASE | _PAGE_KERNEL_RW)
#define _PAGE_BASE (_PAGE_BASE_NC)
#define _PAGE_BASE_NC (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_PSIZE)
Also, in pte-common.h, maybe the following defines could/should be
reworked once you serie applied, shouldn't it ?
/* Protection used for kernel text. We want the debuggers to be able to
* set breakpoints anywhere, so don't write protect the kernel text
* on platforms where such control is possible.
*/
#if defined(CONFIG_KGDB) || defined(CONFIG_XMON) ||
defined(CONFIG_BDI_SWITCH) ||\
defined(CONFIG_KPROBES) || defined(CONFIG_DYNAMIC_FTRACE)
#define PAGE_KERNEL_TEXT PAGE_KERNEL_X
#else
#define PAGE_KERNEL_TEXT PAGE_KERNEL_ROX
#endif
Christophe
---
L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel
antivirus Avast.
https://www.avast.com/antivirus
