linux-kernel - [RFC][PATCH 21/36] objtool: mcount: Restrict using ehdr in append

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Date:   Fri, 10 Apr 2020 12:35:44 -0700
From:   Matt Helsley <mhelsley@...are.com>
To:     <linux-kernel@...r.kernel.org>
CC:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Julien Thierry <jthierry@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Matt Helsley <mhelsley@...are.com>
Subject: [RFC][PATCH 21/36] objtool: mcount: Restrict using ehdr in append_func()

To use as a pointer to an ehdr to modify. Extract the
read-only bits from objtool's GElf_Ehdr.

Signed-off-by: Matt Helsley <mhelsley@...are.com>
---
 tools/objtool/recordmcount.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/recordmcount.h b/tools/objtool/recordmcount.h
index 3c7afb9a2eac..3c98c379f472 100644
--- a/tools/objtool/recordmcount.h
+++ b/tools/objtool/recordmcount.h
@@ -99,8 +99,8 @@ static int append_func(Elf_Ehdr *const ehdr,
 	char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
 		? ".rela__mcount_loc"
 		:  ".rel__mcount_loc";
-	unsigned const old_shnum = w2(ehdr->e_shnum);
-	uint_t const old_shoff = _w(ehdr->e_shoff);
+	unsigned const old_shnum = lf->ehdr.e_shnum;
+	uint_t const old_shoff = lf->ehdr.e_shoff;
 	uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
 	uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
 	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
@@ -167,7 +167,7 @@ static int append_func(Elf_Ehdr *const ehdr,
 		return -1;
 
 	ehdr->e_shoff = _w(new_e_shoff);
-	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum));  /* {.rel,}__mcount_loc */
+	ehdr->e_shnum = w2(2 + lf->ehdr.e_shnum);  /* {.rel,}__mcount_loc */
 	if (ulseek(0, SEEK_SET) < 0)
 		return -1;
 	if (uwrite(ehdr, sizeof(*ehdr)) < 0)
-- 
2.20.1