objtool: Add ORC unwind table generation

Now that objtool knows the states of all registers on the stack for each
instruction, it's straightforward to generate debuginfo for an unwinder
to use.

Instead of generating DWARF, generate a new format called ORC, which is
more suitable for an in-kernel unwinder.  See
Documentation/x86/orc-unwinder.txt for a more detailed description of
this new debuginfo format and why it's preferable to DWARF.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/c9b9f01ba6c5ed2bdc9bb0957b78167fdbf9632e.1499786555.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 214 insertions, 0 deletions

diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
new file mode 100644
index 000000000000..e5ca31429c9b
--- /dev/null
+++ b/tools/objtool/orc_gen.c
@@ -0,0 +1,214 @@
+/*
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "orc.h"
+#include "check.h"
+#include "warn.h"
+
+int create_orc(struct objtool_file *file)
+{
+	struct instruction *insn;
+
+	for_each_insn(file, insn) {
+		struct orc_entry *orc = &insn->orc;
+		struct cfi_reg *cfa = &insn->state.cfa;
+		struct cfi_reg *bp = &insn->state.regs[CFI_BP];
+
+		if (cfa->base == CFI_UNDEFINED) {
+			orc->sp_reg = ORC_REG_UNDEFINED;
+			continue;
+		}
+
+		switch (cfa->base) {
+		case CFI_SP:
+			orc->sp_reg = ORC_REG_SP;
+			break;
+		case CFI_SP_INDIRECT:
+			orc->sp_reg = ORC_REG_SP_INDIRECT;
+			break;
+		case CFI_BP:
+			orc->sp_reg = ORC_REG_BP;
+			break;
+		case CFI_BP_INDIRECT:
+			orc->sp_reg = ORC_REG_BP_INDIRECT;
+			break;
+		case CFI_R10:
+			orc->sp_reg = ORC_REG_R10;
+			break;
+		case CFI_R13:
+			orc->sp_reg = ORC_REG_R13;
+			break;
+		case CFI_DI:
+			orc->sp_reg = ORC_REG_DI;
+			break;
+		case CFI_DX:
+			orc->sp_reg = ORC_REG_DX;
+			break;
+		default:
+			WARN_FUNC("unknown CFA base reg %d",
+				  insn->sec, insn->offset, cfa->base);
+			return -1;
+		}
+
+		switch(bp->base) {
+		case CFI_UNDEFINED:
+			orc->bp_reg = ORC_REG_UNDEFINED;
+			break;
+		case CFI_CFA:
+			orc->bp_reg = ORC_REG_PREV_SP;
+			break;
+		case CFI_BP:
+			orc->bp_reg = ORC_REG_BP;
+			break;
+		default:
+			WARN_FUNC("unknown BP base reg %d",
+				  insn->sec, insn->offset, bp->base);
+			return -1;
+		}
+
+		orc->sp_offset = cfa->offset;
+		orc->bp_offset = bp->offset;
+		orc->type = insn->state.type;
+	}
+
+	return 0;
+}
+
+static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
+				unsigned int idx, struct section *insn_sec,
+				unsigned long insn_off, struct orc_entry *o)
+{
+	struct orc_entry *orc;
+	struct rela *rela;
+
+	/* populate ORC data */
+	orc = (struct orc_entry *)u_sec->data->d_buf + idx;
+	memcpy(orc, o, sizeof(*orc));
+
+	/* populate rela for ip */
+	rela = malloc(sizeof(*rela));
+	if (!rela) {
+		perror("malloc");
+		return -1;
+	}
+	memset(rela, 0, sizeof(*rela));
+
+	rela->sym = insn_sec->sym;
+	rela->addend = insn_off;
+	rela->type = R_X86_64_PC32;
+	rela->offset = idx * sizeof(int);
+
+	list_add_tail(&rela->list, &ip_relasec->rela_list);
+	hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);
+
+	return 0;
+}
+
+int create_orc_sections(struct objtool_file *file)
+{
+	struct instruction *insn, *prev_insn;
+	struct section *sec, *u_sec, *ip_relasec;
+	unsigned int idx;
+
+	struct orc_entry empty = {
+		.sp_reg = ORC_REG_UNDEFINED,
+		.bp_reg  = ORC_REG_UNDEFINED,
+		.type    = ORC_TYPE_CALL,
+	};
+
+	sec = find_section_by_name(file->elf, ".orc_unwind");
+	if (sec) {
+		WARN("file already has .orc_unwind section, skipping");
+		return -1;
+	}
+
+	/* count the number of needed orcs */
+	idx = 0;
+	for_each_sec(file, sec) {
+		if (!sec->text)
+			continue;
+
+		prev_insn = NULL;
+		sec_for_each_insn(file, sec, insn) {
+			if (!prev_insn ||
+			    memcmp(&insn->orc, &prev_insn->orc,
+				   sizeof(struct orc_entry))) {
+				idx++;
+			}
+			prev_insn = insn;
+		}
+
+		/* section terminator */
+		if (prev_insn)
+			idx++;
+	}
+	if (!idx)
+		return -1;
+
+
+	/* create .orc_unwind_ip and .rela.orc_unwind_ip sections */
+	sec = elf_create_section(file->elf, ".orc_unwind_ip", sizeof(int), idx);
+
+	ip_relasec = elf_create_rela_section(file->elf, sec);
+	if (!ip_relasec)
+		return -1;
+
+	/* create .orc_unwind section */
+	u_sec = elf_create_section(file->elf, ".orc_unwind",
+				   sizeof(struct orc_entry), idx);
+
+	/* populate sections */
+	idx = 0;
+	for_each_sec(file, sec) {
+		if (!sec->text)
+			continue;
+
+		prev_insn = NULL;
+		sec_for_each_insn(file, sec, insn) {
+			if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,
+						 sizeof(struct orc_entry))) {
+
+				if (create_orc_entry(u_sec, ip_relasec, idx,
+						     insn->sec, insn->offset,
+						     &insn->orc))
+					return -1;
+
+				idx++;
+			}
+			prev_insn = insn;
+		}
+
+		/* section terminator */
+		if (prev_insn) {
+			if (create_orc_entry(u_sec, ip_relasec, idx,
+					     prev_insn->sec,
+					     prev_insn->offset + prev_insn->len,
+					     &empty))
+				return -1;
+
+			idx++;
+		}
+	}
+
+	if (elf_rebuild_rela_section(ip_relasec))
+		return -1;
+
+	return 0;
+}