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Date: Wed, 23 Sep 2020 10:38:58 -0700
From: Kristen Carlson Accardi <kristen@...ux.intel.com>
To: keescook@...omium.org,
tglx@...utronix.de,
mingo@...hat.com,
bp@...en8.de,
x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Arnd Bergmann <arnd@...db.de>
Cc: arjan@...ux.intel.com,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
rick.p.edgecombe@...el.com,
Kristen Carlson Accardi <kristen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
linux-arch@...r.kernel.org
Subject: [PATCH v5 04/10] x86: Make sure _etext includes function sections
When using -ffunction-sections to place each function in
it's own text section so it can be randomized at load time, the
linker considers these .text.* sections "orphaned sections", and
will place them after the first similar section (.text). In order
to accurately represent the end of the text section and the
orphaned sections, _etext must be moved so that it is after both
.text and .text.* The text size must also be calculated to
include .text AND .text.*
Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
arch/x86/kernel/vmlinux.lds.S | 17 +++++++++++++++--
include/asm-generic/vmlinux.lds.h | 2 +-
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 9a03e5b23135..b0718eef283f 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -146,9 +146,22 @@ SECTIONS
#endif
} :text =0xcccc
- /* End of text section, which should occupy whole number of pages */
- _etext = .;
+ /*
+ * -ffunction-sections creates .text.* sections, which are considered
+ * "orphan sections" and added after the first similar section (.text).
+ * Placing this ALIGN statement before _etext causes the address of
+ * _etext to be below that of all the .text.* orphaned sections
+ */
. = ALIGN(PAGE_SIZE);
+ _etext = .;
+
+ /*
+ * the size of the .text section is used to calculate the address
+ * range for orc lookups. If we just use SIZEOF(.text), we will
+ * miss all the .text.* sections. Calculate the size using _etext
+ * and _stext and save the value for later.
+ */
+ text_size = _etext - _stext;
X86_ALIGN_RODATA_BEGIN
RO_DATA(PAGE_SIZE)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index afd5cdf79a3a..6f7239e033e8 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -863,7 +863,7 @@
. = ALIGN(4); \
.orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \
orc_lookup = .; \
- . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \
+ . += (((text_size + LOOKUP_BLOCK_SIZE - 1) / \
LOOKUP_BLOCK_SIZE) + 1) * 4; \
orc_lookup_end = .; \
}
--
2.20.1
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