linux-kernel - [PATCH 4.14 13/95] scripts/recordmcount.{c,pl}: support -ffunction-sections .text.* section names

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Date:   Mon, 15 Mar 2021 14:56:43 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joe Lawrence <joe.lawrence@...hat.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Manoj Gupta <manojgupta@...gle.com>
Subject: [PATCH 4.14 13/95] scripts/recordmcount.{c,pl}: support -ffunction-sections .text.* section names

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Joe Lawrence <joe.lawrence@...hat.com>

commit 9c8e2f6d3d361439cc6744a094f1c15681b55269 upstream.

When building with -ffunction-sections, the compiler will place each
function into its own ELF section, prefixed with ".text".  For example,
a simple test module with functions test_module_do_work() and
test_module_wq_func():

  % objdump --section-headers test_module.o | awk '/\.text/{print $2}'
  .text
  .text.test_module_do_work
  .text.test_module_wq_func
  .init.text
  .exit.text

Adjust the recordmcount scripts to look for ".text" as a section name
prefix.  This will ensure that those functions will be included in the
__mcount_loc relocations:

  % objdump --reloc --section __mcount_loc test_module.o
  OFFSET           TYPE              VALUE
  0000000000000000 R_X86_64_64       .text.test_module_do_work
  0000000000000008 R_X86_64_64       .text.test_module_wq_func
  0000000000000010 R_X86_64_64       .init.text

Link: http://lkml.kernel.org/r/1542745158-25392-2-git-send-email-joe.lawrence@redhat.com

Signed-off-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Cc: Manoj Gupta <manojgupta@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 scripts/recordmcount.c  |    2 +-
 scripts/recordmcount.pl |   13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -415,7 +415,7 @@ static uint32_t (*w2)(uint16_t);
 static int
 is_mcounted_section_name(char const *const txtname)
 {
-	return strcmp(".text",           txtname) == 0 ||
+	return strncmp(".text",          txtname, 5) == 0 ||
 		strcmp(".init.text",     txtname) == 0 ||
 		strcmp(".ref.text",      txtname) == 0 ||
 		strcmp(".sched.text",    txtname) == 0 ||
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -142,6 +142,11 @@ my %text_sections = (
      ".text.unlikely" => 1,
 );
 
+# Acceptable section-prefixes to record.
+my %text_section_prefixes = (
+     ".text." => 1,
+);
+
 # Note: we are nice to C-programmers here, thus we skip the '||='-idiom.
 $objdump = 'objdump' if (!$objdump);
 $objcopy = 'objcopy' if (!$objcopy);
@@ -507,6 +512,14 @@ while (<IN>) {
 
 	# Only record text sections that we know are safe
 	$read_function = defined($text_sections{$1});
+	if (!$read_function) {
+	    foreach my $prefix (keys %text_section_prefixes) {
+	        if (substr($1, 0, length $prefix) eq $prefix) {
+	            $read_function = 1;
+	            last;
+	        }
+	    }
+	}
 	# print out any recorded offsets
 	update_funcs();