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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Randy Dunlap <rdunlap@infradead.org>,
	Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg KH <gregkh@linuxfoundation.org>,
	David Laight <David.Laight@ACULAB.COM>,
	damian <damian.tometzki@icloud.com>
Subject: [PATCH v1.3 3/3] objtool: Support GCC 8 switch tables
Date: Thu, 10 May 2018 17:48:49 -0500	[thread overview]
Message-ID: <20180510224849.xwi34d6tzheb5wgw@treble> (raw)
In-Reply-To: <20180510224516.s7qcjvbolwxkvzqd@treble>


With GCC 8, some issues were found with the objtool switch table
detection.

1) In the .rodata section, immediately after the switch table, there can
   be another object which contains a pointer to the function which had
   the switch statement.  In this case objtool wrongly considers the
   function pointer to be part of the switch table.  Fix it by:

   a) making sure there are no pointers to the beginning of the
      function; and

   b) making sure there are no gaps in the switch table.

   Only the former was needed, the latter adds additional protection for
   future optimizations.

2) In find_switch_table(), case 1 and case 2 are missing the check to
   ensure that the .rodata switch table data is anonymous, i.e. that it
   isn't already associated with an ELF symbol.  Fix it by adding the
   same find_symbol_containing() check which is used for case 3.

This fixes the following warnings with GCC 8:

  drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
  net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
  drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
  drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
  drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
  drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
v1.3: Combine improved patch description from 1.1 with 32-bit host
      cross-compile from 1.2.

 tools/objtool/check.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 14daf6a27d9f..9bb04fddd3c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -810,17 +810,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 	struct rela *rela = table;
 	struct instruction *alt_insn;
 	struct alternative *alt;
+	struct symbol *pfunc = insn->func->pfunc;
+	unsigned int prev_offset = 0;
 
 	list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
 		if (rela == next_table)
 			break;
 
+		/* Make sure the switch table entries are consecutive: */
+		if (prev_offset && rela->offset != prev_offset + 8)
+			break;
+
+		/* Detect function pointers from contiguous objects: */
+		if (rela->sym->sec == pfunc->sec &&
+		    rela->addend == pfunc->offset)
+			break;
+
 		alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (!alt_insn)
 			break;
 
 		/* Make sure the jmp dest is in the function or subfunction: */
-		if (alt_insn->func->pfunc != insn->func->pfunc)
+		if (alt_insn->func->pfunc != pfunc)
 			break;
 
 		alt = malloc(sizeof(*alt));
@@ -831,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 
 		alt->insn = alt_insn;
 		list_add_tail(&alt->list, &insn->alts);
+		prev_offset = rela->offset;
+	}
+
+	if (!prev_offset) {
+		WARN_FUNC("can't find switch jump table",
+			  insn->sec, insn->offset);
+		return -1;
 	}
 
 	return 0;
@@ -887,7 +905,9 @@ static struct rela *find_switch_table(struct objtool_file *file,
 	struct instruction *orig_insn = insn;
 
 	text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-	if (text_rela && text_rela->sym == file->rodata->sym) {
+	if (text_rela && text_rela->sym == file->rodata->sym &&
+	    !find_symbol_containing(file->rodata, text_rela->addend)) {
+
 		/* case 1 */
 		rodata_rela = find_rela_by_dest(file->rodata,
 						text_rela->addend);
-- 
2.17.0

  reply	other threads:[~2018-05-10 22:48 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-10  3:39 [PATCH 0/3] objtool: GCC 8 support Josh Poimboeuf
2018-05-10  3:39 ` [PATCH 1/3] objtool: Fix "noreturn" detection for recursive sibling calls Josh Poimboeuf
2018-05-14 12:37   ` [tip:core/urgent] " tip-bot for Josh Poimboeuf
2018-05-10  3:39 ` [PATCH 2/3] objtool: Support GCC 8 cold subfunctions Josh Poimboeuf
2018-05-14 12:37   ` [tip:core/urgent] objtool: Support GCC 8's " tip-bot for Josh Poimboeuf
2018-05-10  3:39 ` [PATCH 3/3] objtool: Support GCC 8 switch tables Josh Poimboeuf
2018-05-10  8:41   ` Peter Zijlstra
2018-05-10 12:44     ` [PATCH v1.1 " Josh Poimboeuf
2018-05-10 14:07       ` Peter Zijlstra
2018-05-10 22:45       ` [PATCH v1.2 " Josh Poimboeuf
2018-05-10 22:48         ` Josh Poimboeuf [this message]
2018-05-14 12:38           ` [tip:core/urgent] " tip-bot for Josh Poimboeuf

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