linux-kernel - [PATCH v2] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S

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Message-Id: <20200110215005.2164353-1-nivedita@alum.mit.edu>
Date:   Fri, 10 Jan 2020 16:50:05 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        Thomas Lendacky <Thomas.Lendacky@....com>
Subject: [PATCH v2] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL

Prior to binutiles-2.23, ld treats the location counter as absolute if
used outside an output section definition. From version 2.23 onwards,
the location counter is treated as relative to an adjacent output
section (usually the previous one, unless there isn't one or the
location counter has been assigned to previously, in which case the next
one).

The result is that a symbol definition in the linker script, such as
	_etext = .;
that appears outside an output section definition makes _etext an
absolute symbol prior to binutils-2.23 and a relative symbol from
version 2.23 onwards. So when using a 2.21 or 2.22 vintage linker, the
build fails with
	Invalid absolute R_X86_64_32S relocation: _etext
for x86-64, and a similar message with R_386_32 for x86-32.

Fix this by adding these symbols to S_REL to tell the relocs tool that
these should always be treated as relative symbols needing relocation.

Fixes: b907693883fd ("x86/vmlinux: Actually use _etext for the end of the text segment")
Fixes: c603a309cc75 ("x86/mm: Identify the end of the kernel area to be reserved")
Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
v2: Added a more detailed commit message

 arch/x86/tools/relocs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index ce7188cbdae5..0a6146d6414f 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -78,6 +78,8 @@ static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 	"__end_rodata_hpage_align|"
 #endif
 	"__vvar_page|"
+	"_etext|"
+	"__end_of_kernel_reserve|"
 	"_end)$"
 };
 
-- 
2.24.1