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arm64: use fixmap for text patching

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When kernel text is marked as read only, it cannot be modified directly.
Use a fixmap to modify the text instead in a similar manner to
x86 and arm.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Laura Abbott 2015-01-22 01:36:05 +00:00 • committed by Catalin Marinas
commit 2f896d5866
2 changed files with 47 additions and 1 deletions
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1
arch/arm64/include/asm/fixmap.h
View file

@ -49,6 +49,7 @@ enum fixed_addresses {
FIX_BTMAP_END = __end_of_permanent_fixed_addresses,
FIX_BTMAP_BEGIN = FIX_BTMAP_END + TOTAL_FIX_BTMAPS - 1,
FIX_TEXT_POKE0,
__end_of_fixed_addresses
};

47
arch/arm64/kernel/insn.c
View file

@ -17,14 +17,19 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/stop_machine.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>
#include <asm/fixmap.h>
#include <asm/insn.h>
#define AARCH64_INSN_SF_BIT BIT(31)
@ -72,6 +77,29 @@ bool __kprobes aarch64_insn_is_nop(u32 insn)
}
}
static DEFINE_SPINLOCK(patch_lock);
static void __kprobes *patch_map(void *addr, int fixmap)
{
unsigned long uintaddr = (uintptr_t) addr;
bool module = !core_kernel_text(uintaddr);
struct page *page;
if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
page = vmalloc_to_page(addr);
else
page = virt_to_page(addr);
BUG_ON(!page);
set_fixmap(fixmap, page_to_phys(page));
return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
}
static void __kprobes patch_unmap(int fixmap)
{
clear_fixmap(fixmap);
}
/*
* In ARMv8-A, A64 instructions have a fixed length of 32 bits and are always
* little-endian.
@ -88,10 +116,27 @@ int __kprobes aarch64_insn_read(void *addr, u32 *insnp)
return ret;
}
static int __kprobes __aarch64_insn_write(void *addr, u32 insn)
{
void *waddr = addr;
unsigned long flags = 0;
int ret;
spin_lock_irqsave(&patch_lock, flags);
waddr = patch_map(addr, FIX_TEXT_POKE0);
ret = probe_kernel_write(waddr, &insn, AARCH64_INSN_SIZE);
patch_unmap(FIX_TEXT_POKE0);
spin_unlock_irqrestore(&patch_lock, flags);
return ret;
}
int __kprobes aarch64_insn_write(void *addr, u32 insn)
{
insn = cpu_to_le32(insn);
return probe_kernel_write(addr, &insn, AARCH64_INSN_SIZE);
return __aarch64_insn_write(addr, insn);
}
static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)