LoongArch: Add KFENCE (Kernel Electric-Fence) support

The LoongArch architecture is quite different from other architectures.
When the allocating of KFENCE itself is done, it is mapped to the direct
mapping configuration window [1] by default on LoongArch.  It means that
it is not possible to use the page table mapped mode which required by
the KFENCE system and therefore it should be remapped to the appropriate
region.

This patch adds architecture specific implementation details for KFENCE.
In particular, this implements the required interface in <asm/kfence.h>.

Tested this patch by running the testcases and all passed.

[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#virtual-address-space-and-address-translation-mode

Signed-off-by: Enze Li <lienze@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 14 insertions, 8 deletions

diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index da5b6d518cdb..e6376e3dce86 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -23,6 +23,7 @@
 #include <linux/kprobes.h>
 #include <linux/perf_event.h>
 #include <linux/uaccess.h>
+#include <linux/kfence.h>
 
 #include <asm/branch.h>
 #include <asm/mmu_context.h>
@@ -30,7 +31,8 @@
 
 int show_unhandled_signals = 1;
 
-static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
+static void __kprobes no_context(struct pt_regs *regs,
+			unsigned long write, unsigned long address)
 {
 	const int field = sizeof(unsigned long) * 2;
 
@@ -38,6 +40,9 @@ static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
 	if (fixup_exception(regs))
 		return;
 
+	if (kfence_handle_page_fault(address, write, regs))
+		return;
+
 	/*
 	 * Oops. The kernel tried to access some bad page. We'll have to
 	 * terminate things with extreme prejudice.
@@ -51,14 +56,15 @@ static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
 	die("Oops", regs);
 }
 
-static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address)
+static void __kprobes do_out_of_memory(struct pt_regs *regs,
+			unsigned long write, unsigned long address)
 {
 	/*
 	 * We ran out of memory, call the OOM killer, and return the userspace
 	 * (which will retry the fault, or kill us if we got oom-killed).
 	 */
 	if (!user_mode(regs)) {
-		no_context(regs, address);
+		no_context(regs, write, address);
 		return;
 	}
 	pagefault_out_of_memory();
@@ -69,7 +75,7 @@ static void __kprobes do_sigbus(struct pt_regs *regs,
 {
 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs)) {
-		no_context(regs, address);
+		no_context(regs, write, address);
 		return;
 	}
 
@@ -90,7 +96,7 @@ static void __kprobes do_sigsegv(struct pt_regs *regs,
 
 	/* Kernel mode? Handle exceptions or die */
 	if (!user_mode(regs)) {
-		no_context(regs, address);
+		no_context(regs, write, address);
 		return;
 	}
 
@@ -149,7 +155,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 	 */
 	if (address & __UA_LIMIT) {
 		if (!user_mode(regs))
-			no_context(regs, address);
+			no_context(regs, write, address);
 		else
 			do_sigsegv(regs, write, address, si_code);
 		return;
@@ -211,7 +217,7 @@ good_area:
 
 	if (fault_signal_pending(fault, regs)) {
 		if (!user_mode(regs))
-			no_context(regs, address);
+			no_context(regs, write, address);
 		return;
 	}
 
@@ -232,7 +238,7 @@ good_area:
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		mmap_read_unlock(mm);
 		if (fault & VM_FAULT_OOM) {
-			do_out_of_memory(regs, address);
+			do_out_of_memory(regs, write, address);
 			return;
 		} else if (fault & VM_FAULT_SIGSEGV) {
 			do_sigsegv(regs, write, address, si_code);