1 files changed, 252 insertions, 0 deletions
diff --git a/arch/x86/events/utils.c b/arch/x86/events/utils.c
new file mode 100644
index 000000000..dab4ed199
--- /dev/null
+++ b/arch/x86/events/utils.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <asm/insn.h>
+#include <linux/mm.h>
+
+#include "perf_event.h"
+
+static int decode_branch_type(struct insn *insn)
+{
+	int ext;
+
+	if (insn_get_opcode(insn))
+		return X86_BR_ABORT;
+
+	switch (insn->opcode.bytes[0]) {
+	case 0xf:
+		switch (insn->opcode.bytes[1]) {
+		case 0x05: /* syscall */
+		case 0x34: /* sysenter */
+			return X86_BR_SYSCALL;
+		case 0x07: /* sysret */
+		case 0x35: /* sysexit */
+			return X86_BR_SYSRET;
+		case 0x80 ... 0x8f: /* conditional */
+			return X86_BR_JCC;
+		}
+		return X86_BR_NONE;
+	case 0x70 ... 0x7f: /* conditional */
+		return X86_BR_JCC;
+	case 0xc2: /* near ret */
+	case 0xc3: /* near ret */
+	case 0xca: /* far ret */
+	case 0xcb: /* far ret */
+		return X86_BR_RET;
+	case 0xcf: /* iret */
+		return X86_BR_IRET;
+	case 0xcc ... 0xce: /* int */
+		return X86_BR_INT;
+	case 0xe8: /* call near rel */
+		if (insn_get_immediate(insn) || insn->immediate1.value == 0) {
+			/* zero length call */
+			return X86_BR_ZERO_CALL;
+		}
+		fallthrough;
+	case 0x9a: /* call far absolute */
+		return X86_BR_CALL;
+	case 0xe0 ... 0xe3: /* loop jmp */
+		return X86_BR_JCC;
+	case 0xe9 ... 0xeb: /* jmp */
+		return X86_BR_JMP;
+	case 0xff: /* call near absolute, call far absolute ind */
+		if (insn_get_modrm(insn))
+			return X86_BR_ABORT;
+
+		ext = (insn->modrm.bytes[0] >> 3) & 0x7;
+		switch (ext) {
+		case 2: /* near ind call */
+		case 3: /* far ind call */
+			return X86_BR_IND_CALL;
+		case 4:
+		case 5:
+			return X86_BR_IND_JMP;
+		}
+		return X86_BR_NONE;
+	}
+
+	return X86_BR_NONE;
+}
+
+/*
+ * return the type of control flow change at address "from"
+ * instruction is not necessarily a branch (in case of interrupt).
+ *
+ * The branch type returned also includes the priv level of the
+ * target of the control flow change (X86_BR_USER, X86_BR_KERNEL).
+ *
+ * If a branch type is unknown OR the instruction cannot be
+ * decoded (e.g., text page not present), then X86_BR_NONE is
+ * returned.
+ *
+ * While recording branches, some processors can report the "from"
+ * address to be that of an instruction preceding the actual branch
+ * when instruction fusion occurs. If fusion is expected, attempt to
+ * find the type of the first branch instruction within the next
+ * MAX_INSN_SIZE bytes and if found, provide the offset between the
+ * reported "from" address and the actual branch instruction address.
+ */
+static int get_branch_type(unsigned long from, unsigned long to, int abort,
+			   bool fused, int *offset)
+{
+	struct insn insn;
+	void *addr;
+	int bytes_read, bytes_left, insn_offset;
+	int ret = X86_BR_NONE;
+	int to_plm, from_plm;
+	u8 buf[MAX_INSN_SIZE];
+	int is64 = 0;
+
+	/* make sure we initialize offset */
+	if (offset)
+		*offset = 0;
+
+	to_plm = kernel_ip(to) ? X86_BR_KERNEL : X86_BR_USER;
+	from_plm = kernel_ip(from) ? X86_BR_KERNEL : X86_BR_USER;
+
+	/*
+	 * maybe zero if lbr did not fill up after a reset by the time
+	 * we get a PMU interrupt
+	 */
+	if (from == 0 || to == 0)
+		return X86_BR_NONE;
+
+	if (abort)
+		return X86_BR_ABORT | to_plm;
+
+	if (from_plm == X86_BR_USER) {
+		/*
+		 * can happen if measuring at the user level only
+		 * and we interrupt in a kernel thread, e.g., idle.
+		 */
+		if (!current->mm)
+			return X86_BR_NONE;
+
+		/* may fail if text not present */
+		bytes_left = copy_from_user_nmi(buf, (void __user *)from,
+						MAX_INSN_SIZE);
+		bytes_read = MAX_INSN_SIZE - bytes_left;
+		if (!bytes_read)
+			return X86_BR_NONE;
+
+		addr = buf;
+	} else {
+		/*
+		 * The LBR logs any address in the IP, even if the IP just
+		 * faulted. This means userspace can control the from address.
+		 * Ensure we don't blindly read any address by validating it is
+		 * a known text address and not a vsyscall address.
+		 */
+		if (kernel_text_address(from) && !in_gate_area_no_mm(from)) {
+			addr = (void *)from;
+			/*
+			 * Assume we can get the maximum possible size
+			 * when grabbing kernel data.  This is not
+			 * _strictly_ true since we could possibly be
+			 * executing up next to a memory hole, but
+			 * it is very unlikely to be a problem.
+			 */
+			bytes_read = MAX_INSN_SIZE;
+		} else {
+			return X86_BR_NONE;
+		}
+	}
+
+	/*
+	 * decoder needs to know the ABI especially
+	 * on 64-bit systems running 32-bit apps
+	 */
+#ifdef CONFIG_X86_64
+	is64 = kernel_ip((unsigned long)addr) || any_64bit_mode(current_pt_regs());
+#endif
+	insn_init(&insn, addr, bytes_read, is64);
+	ret = decode_branch_type(&insn);
+	insn_offset = 0;
+
+	/* Check for the possibility of branch fusion */
+	while (fused && ret == X86_BR_NONE) {
+		/* Check for decoding errors */
+		if (insn_get_length(&insn) || !insn.length)
+			break;
+
+		insn_offset += insn.length;
+		bytes_read -= insn.length;
+		if (bytes_read < 0)
+			break;
+
+		insn_init(&insn, addr + insn_offset, bytes_read, is64);
+		ret = decode_branch_type(&insn);
+	}
+
+	if (offset)
+		*offset = insn_offset;
+
+	/*
+	 * interrupts, traps, faults (and thus ring transition) may
+	 * occur on any instructions. Thus, to classify them correctly,
+	 * we need to first look at the from and to priv levels. If they
+	 * are different and to is in the kernel, then it indicates
+	 * a ring transition. If the from instruction is not a ring
+	 * transition instr (syscall, systenter, int), then it means
+	 * it was a irq, trap or fault.
+	 *
+	 * we have no way of detecting kernel to kernel faults.
+	 */
+	if (from_plm == X86_BR_USER && to_plm == X86_BR_KERNEL
+	    && ret != X86_BR_SYSCALL && ret != X86_BR_INT)
+		ret = X86_BR_IRQ;
+
+	/*
+	 * branch priv level determined by target as
+	 * is done by HW when LBR_SELECT is implemented
+	 */
+	if (ret != X86_BR_NONE)
+		ret |= to_plm;
+
+	return ret;
+}
+
+int branch_type(unsigned long from, unsigned long to, int abort)
+{
+	return get_branch_type(from, to, abort, false, NULL);
+}
+
+int branch_type_fused(unsigned long from, unsigned long to, int abort,
+		      int *offset)
+{
+	return get_branch_type(from, to, abort, true, offset);
+}
+
+#define X86_BR_TYPE_MAP_MAX	16
+
+static int branch_map[X86_BR_TYPE_MAP_MAX] = {
+	PERF_BR_CALL,		/* X86_BR_CALL */
+	PERF_BR_RET,		/* X86_BR_RET */
+	PERF_BR_SYSCALL,	/* X86_BR_SYSCALL */
+	PERF_BR_SYSRET,		/* X86_BR_SYSRET */
+	PERF_BR_UNKNOWN,	/* X86_BR_INT */
+	PERF_BR_ERET,		/* X86_BR_IRET */
+	PERF_BR_COND,		/* X86_BR_JCC */
+	PERF_BR_UNCOND,		/* X86_BR_JMP */
+	PERF_BR_IRQ,		/* X86_BR_IRQ */
+	PERF_BR_IND_CALL,	/* X86_BR_IND_CALL */
+	PERF_BR_UNKNOWN,	/* X86_BR_ABORT */
+	PERF_BR_UNKNOWN,	/* X86_BR_IN_TX */
+	PERF_BR_NO_TX,		/* X86_BR_NO_TX */
+	PERF_BR_CALL,		/* X86_BR_ZERO_CALL */
+	PERF_BR_UNKNOWN,	/* X86_BR_CALL_STACK */
+	PERF_BR_IND,		/* X86_BR_IND_JMP */
+};
+
+int common_branch_type(int type)
+{
+	int i;
+
+	type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */
+
+	if (type) {
+		i = __ffs(type);
+		if (i < X86_BR_TYPE_MAP_MAX)
+			return branch_map[i];
+	}
+
+	return PERF_BR_UNKNOWN;
+}