arm64 fixes for -rc3

- Fix early use of kprobes
 
 - Fix kernel placement in kexec_file_load()
 
 - Bump maximum number of NUMA nodes
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Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "Here's the weekly batch of fixes for arm64. Not an awful lot here, but
  there are still a few unresolved issues relating to CPU hotplug, RCU
  and IRQ tracing that I hope to queue fixes for next week.

  Summary:

   - Fix early use of kprobes

   - Fix kernel placement in kexec_file_load()

   - Bump maximum number of NUMA nodes"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: kexec_file: try more regions if loading segments fails
  arm64: kprobes: Use BRK instead of single-step when executing instructions out-of-line
  arm64: NUMA: Kconfig: Increase NODES_SHIFT to 4

arch/arm64/Kconfig

@@ -1002,7 +1002,7 @@ config NUMA
 config NODES_SHIFT
 	int "Maximum NUMA Nodes (as a power of 2)"
 	range 1 10
-	default "2"
+	default "4"
 	depends on NEED_MULTIPLE_NODES
 	help
 	  Specify the maximum number of NUMA Nodes available on the target

arch/arm64/include/asm/brk-imm.h

@@ -10,6 +10,7 @@
  * #imm16 values used for BRK instruction generation
  * 0x004: for installing kprobes
  * 0x005: for installing uprobes
+ * 0x006: for kprobe software single-step
  * Allowed values for kgdb are 0x400 - 0x7ff
  * 0x100: for triggering a fault on purpose (reserved)
  * 0x400: for dynamic BRK instruction
@@ -19,6 +20,7 @@
  */
 #define KPROBES_BRK_IMM			0x004
 #define UPROBES_BRK_IMM			0x005
+#define KPROBES_BRK_SS_IMM		0x006
 #define FAULT_BRK_IMM			0x100
 #define KGDB_DYN_DBG_BRK_IMM		0x400
 #define KGDB_COMPILED_DBG_BRK_IMM	0x401

arch/arm64/include/asm/debug-monitors.h

@@ -53,6 +53,7 @@
 
 /* kprobes BRK opcodes with ESR encoding  */
 #define BRK64_OPCODE_KPROBES	(AARCH64_BREAK_MON | (KPROBES_BRK_IMM << 5))
+#define BRK64_OPCODE_KPROBES_SS	(AARCH64_BREAK_MON | (KPROBES_BRK_SS_IMM << 5))
 /* uprobes BRK opcodes with ESR encoding  */
 #define BRK64_OPCODE_UPROBES	(AARCH64_BREAK_MON | (UPROBES_BRK_IMM << 5))
 

arch/arm64/include/asm/kprobes.h

@@ -16,7 +16,7 @@
 #include <linux/percpu.h>
 
 #define __ARCH_WANT_KPROBES_INSN_SLOT
-#define MAX_INSN_SIZE			1
+#define MAX_INSN_SIZE			2
 
 #define flush_insn_slot(p)		do { } while (0)
 #define kretprobe_blacklist_size	0

arch/arm64/kernel/kexec_image.c

@@ -43,7 +43,7 @@ static void *image_load(struct kimage *image,
 	u64 flags, value;
 	bool be_image, be_kernel;
 	struct kexec_buf kbuf;
-	unsigned long text_offset;
+	unsigned long text_offset, kernel_segment_number;
 	struct kexec_segment *kernel_segment;
 	int ret;
 
@@ -88,11 +88,37 @@ static void *image_load(struct kimage *image,
 	/* Adjust kernel segment with TEXT_OFFSET */
 	kbuf.memsz += text_offset;
 
-	ret = kexec_add_buffer(&kbuf);
+	kernel_segment_number = image->nr_segments;
-	if (ret)
-		return ERR_PTR(ret);
 
-	kernel_segment = &image->segment[image->nr_segments - 1];
+	/*
+	 * The location of the kernel segment may make it impossible to satisfy
+	 * the other segment requirements, so we try repeatedly to find a
+	 * location that will work.
+	 */
+	while ((ret = kexec_add_buffer(&kbuf)) == 0) {
+		/* Try to load additional data */
+		kernel_segment = &image->segment[kernel_segment_number];
+		ret = load_other_segments(image, kernel_segment->mem,
+					  kernel_segment->memsz, initrd,
+					  initrd_len, cmdline);
+		if (!ret)
+			break;
+
+		/*
+		 * We couldn't find space for the other segments; erase the
+		 * kernel segment and try the next available hole.
+		 */
+		image->nr_segments -= 1;
+		kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz;
+		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	}
+
+	if (ret) {
+		pr_err("Could not find any suitable kernel location!");
+		return ERR_PTR(ret);
+	}
+
+	kernel_segment = &image->segment[kernel_segment_number];
 	kernel_segment->mem += text_offset;
 	kernel_segment->memsz -= text_offset;
 	image->start = kernel_segment->mem;
@@ -101,12 +127,7 @@ static void *image_load(struct kimage *image,
 				kernel_segment->mem, kbuf.bufsz,
 				kernel_segment->memsz);
 
-	/* Load additional data */
+	return 0;
-	ret = load_other_segments(image,
-				kernel_segment->mem, kernel_segment->memsz,
-				initrd, initrd_len, cmdline);
-
-	return ERR_PTR(ret);
 }
 
 #ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG

arch/arm64/kernel/machine_kexec_file.c

@@ -240,6 +240,11 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	return ret;
 }
 
+/*
+ * Tries to add the initrd and DTB to the image. If it is not possible to find
+ * valid locations, this function will undo changes to the image and return non
+ * zero.
+ */
 int load_other_segments(struct kimage *image,
 			unsigned long kernel_load_addr,
 			unsigned long kernel_size,
@@ -248,7 +253,8 @@ int load_other_segments(struct kimage *image,
 {
 	struct kexec_buf kbuf;
 	void *headers, *dtb = NULL;
-	unsigned long headers_sz, initrd_load_addr = 0, dtb_len;
+	unsigned long headers_sz, initrd_load_addr = 0, dtb_len,
+		      orig_segments = image->nr_segments;
 	int ret = 0;
 
 	kbuf.image = image;
@@ -334,6 +340,7 @@ int load_other_segments(struct kimage *image,
 	return 0;
 
 out_err:
+	image->nr_segments = orig_segments;
 	vfree(dtb);
 	return ret;
 }

arch/arm64/kernel/probes/kprobes.c

@@ -36,25 +36,16 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 static void __kprobes
 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
 
-static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
-{
-	void *addrs[1];
-	u32 insns[1];
-
-	addrs[0] = addr;
-	insns[0] = opcode;
-
-	return aarch64_insn_patch_text(addrs, insns, 1);
-}
-
 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 {
-	/* prepare insn slot */
+	kprobe_opcode_t *addr = p->ainsn.api.insn;
-	patch_text(p->ainsn.api.insn, p->opcode);
+	void *addrs[] = {addr, addr + 1};
+	u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS};
 
-	flush_icache_range((uintptr_t) (p->ainsn.api.insn),
+	/* prepare insn slot */
-			   (uintptr_t) (p->ainsn.api.insn) +
+	aarch64_insn_patch_text(addrs, insns, 2);
-			   MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+
+	flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
 
 	/*
 	 * Needs restoring of return address after stepping xol.
@@ -128,13 +119,18 @@ void *alloc_insn_page(void)
 /* arm kprobe: install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	patch_text(p->addr, BRK64_OPCODE_KPROBES);
+	void *addr = p->addr;
+	u32 insn = BRK64_OPCODE_KPROBES;
+
+	aarch64_insn_patch_text(&addr, &insn, 1);
 }
 
 /* disarm kprobe: remove breakpoint from text */
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
-	patch_text(p->addr, p->opcode);
+	void *addr = p->addr;
+
+	aarch64_insn_patch_text(&addr, &p->opcode, 1);
 }
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)
@@ -163,20 +159,15 @@ static void __kprobes set_current_kprobe(struct kprobe *p)
 }
 
 /*
- * Interrupts need to be disabled before single-step mode is set, and not
+ * Mask all of DAIF while executing the instruction out-of-line, to keep things
- * reenabled until after single-step mode ends.
+ * simple and avoid nesting exceptions. Interrupts do have to be disabled since
- * Without disabling interrupt on local CPU, there is a chance of
+ * the kprobe state is per-CPU and doesn't get migrated.
- * interrupt occurrence in the period of exception return and  start of
- * out-of-line single-step, that result in wrongly single stepping
- * into the interrupt handler.
  */
 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 						struct pt_regs *regs)
 {
 	kcb->saved_irqflag = regs->pstate & DAIF_MASK;
-	regs->pstate |= PSR_I_BIT;
+	regs->pstate |= DAIF_MASK;
-	/* Unmask PSTATE.D for enabling software step exceptions. */
-	regs->pstate &= ~PSR_D_BIT;
 }
 
 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
@@ -219,10 +210,7 @@ static void __kprobes setup_singlestep(struct kprobe *p,
 		slot = (unsigned long)p->ainsn.api.insn;
 
 		set_ss_context(kcb, slot);	/* mark pending ss */
-
-		/* IRQs and single stepping do not mix well. */
 		kprobes_save_local_irqflag(kcb, regs);
-		kernel_enable_single_step(regs);
 		instruction_pointer_set(regs, slot);
 	} else {
 		/* insn simulation */
@@ -273,12 +261,8 @@ post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 	}
 	/* call post handler */
 	kcb->kprobe_status = KPROBE_HIT_SSDONE;
-	if (cur->post_handler)	{
+	if (cur->post_handler)
-		/* post_handler can hit breakpoint and single step
-		 * again, so we enable D-flag for recursive exception.
-		 */
 		cur->post_handler(cur, regs, 0);
-	}
 
 	reset_current_kprobe();
 }
@@ -302,8 +286,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
 		if (!instruction_pointer(regs))
 			BUG();
 
-		kernel_disable_single_step();
-
 		if (kcb->kprobe_status == KPROBE_REENTER)
 			restore_previous_kprobe(kcb);
 		else
@@ -365,10 +347,6 @@ static void __kprobes kprobe_handler(struct pt_regs *regs)
 			 * pre-handler and it returned non-zero, it will
 			 * modify the execution path and no need to single
 			 * stepping. Let's just reset current kprobe and exit.
-			 *
-			 * pre_handler can hit a breakpoint and can step thru
-			 * before return, keep PSTATE D-flag enabled until
-			 * pre_handler return back.
 			 */
 			if (!p->pre_handler || !p->pre_handler(p, regs)) {
 				setup_singlestep(p, regs, kcb, 0);
@@ -399,7 +377,7 @@ kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
 }
 
 static int __kprobes
-kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
+kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr)
 {
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	int retval;
@@ -409,16 +387,15 @@ kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
 
 	if (retval == DBG_HOOK_HANDLED) {
 		kprobes_restore_local_irqflag(kcb, regs);
-		kernel_disable_single_step();
-
 		post_kprobe_handler(kcb, regs);
 	}
 
 	return retval;
 }
 
-static struct step_hook kprobes_step_hook = {
+static struct break_hook kprobes_break_ss_hook = {
-	.fn = kprobe_single_step_handler,
+	.imm = KPROBES_BRK_SS_IMM,
+	.fn = kprobe_breakpoint_ss_handler,
 };
 
 static int __kprobes
@@ -486,7 +463,7 @@ int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 int __init arch_init_kprobes(void)
 {
 	register_kernel_break_hook(&kprobes_break_hook);
-	register_kernel_step_hook(&kprobes_step_hook);
+	register_kernel_break_hook(&kprobes_break_ss_hook);
 
 	return 0;
 }