mail archive of the barebox mailing list
 help / color / mirror / Atom feed
From: Sascha Hauer <s.hauer@pengutronix.de>
To: barebox@lists.infradead.org
Subject: [PATCH 3/6] ARM: provide accessor functions for linker variables
Date: Mon,  4 Mar 2013 21:03:06 +0100	[thread overview]
Message-ID: <1362427389-2144-4-git-send-email-s.hauer@pengutronix.de> (raw)
In-Reply-To: <1362427389-2144-1-git-send-email-s.hauer@pengutronix.de>

With relocatable binaries the linker is not able to supply absolute
addresses. These only get available when the relocation function is
being run. Since for early initialization we need some variables
before relocation, we supply them relatively to some known address
in the binary. This means that the variables have to be converted
to absolute addresses during runtime.

This patch adds a C macro and an assembly macro to calculate the
variables during runtime.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/include/asm/sections.h | 33 +++++++++++++++++++++++++++++++++
 arch/arm/lib/runtime-offset.S   | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/arch/arm/include/asm/sections.h b/arch/arm/include/asm/sections.h
index 2b8c516..8c7bc8c 100644
--- a/arch/arm/include/asm/sections.h
+++ b/arch/arm/include/asm/sections.h
@@ -1 +1,34 @@
+#ifndef __ASM_SECTIONS_H
+#define __ASM_SECTIONS_H
+
+#ifndef __ASSEMBLY__
 #include <asm-generic/sections.h>
+
+/*
+ * Access a linker supplied variable. Use this if your code might not be running
+ * at the address it is linked at.
+ */
+#define ld_var(name) ({ \
+	unsigned long __ld_var_##name(void); \
+	__ld_var_##name(); \
+})
+
+#else
+
+/*
+ * Access a linker supplied variable, assembler macro version
+ */
+.macro ld_var name, reg, scratch
+	1000:
+		ldr \reg, 1001f
+		ldr \scratch, =1000b
+		add \reg, \reg, \scratch
+		b 1002f
+	1001:
+		.word \name - 1000b
+	1002:
+.endm
+
+#endif
+
+#endif /* __ASM_SECTIONS_H */
diff --git a/arch/arm/lib/runtime-offset.S b/arch/arm/lib/runtime-offset.S
index ffa668c..15bf414 100644
--- a/arch/arm/lib/runtime-offset.S
+++ b/arch/arm/lib/runtime-offset.S
@@ -1,6 +1,8 @@
 #include <linux/linkage.h>
 #include <asm/assembler.h>
 
+.section ".text_bare_init","ax"
+
 /*
  * Get the offset between the link address and the address
  * we are currently running at.
@@ -15,3 +17,33 @@ THUMB(	subs r0, r0, #1)
 linkadr:
 .word get_runtime_offset
 ENDPROC(get_runtime_offset)
+
+.globl __ld_var_base
+__ld_var_base:
+
+/*
+ * Functions to calculate selected linker supplied variables during runtime.
+ * This is needed for relocatable binaries when the linker variables are
+ * needed before finxing up the relocations.
+ */
+.macro ld_var_entry name
+	ENTRY(__ld_var_\name)
+		ldr r0, __\name
+		b 1f
+	__\name: .word \name - __ld_var_base
+	ENDPROC(__ld_var_\name)
+.endm
+
+ld_var_entry _text
+ld_var_entry __rel_dyn_start
+ld_var_entry __rel_dyn_end
+ld_var_entry __dynsym_start
+ld_var_entry __dynsym_end
+ld_var_entry _barebox_image_size
+ld_var_entry __bss_start
+ld_var_entry __bss_stop
+
+1:
+	ldr r1, =__ld_var_base
+	adds r0, r0, r1
+	mov pc, lr
-- 
1.8.2.rc2


_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox

  parent reply	other threads:[~2013-03-04 20:03 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-04 20:03 [PATCH] ARM: Add relocatable binary support Sascha Hauer
2013-03-04 20:03 ` [PATCH 1/6] ARM: make cpu architecture detection available as static inline function Sascha Hauer
2013-03-04 20:46   ` Alexander Aring
2013-03-05 10:34     ` Sascha Hauer
2013-03-04 20:03 ` [PATCH 2/6] ARM: add early mmu cache flush function and use it in setup_c Sascha Hauer
2013-03-04 20:03 ` Sascha Hauer [this message]
2013-03-04 20:03 ` [PATCH 4/6] ARM boards: Use accessor functions to access linker variables Sascha Hauer
2013-03-04 20:03 ` [PATCH 5/6] ARN: fixup vector addresses for relocatable binaries Sascha Hauer
2013-03-04 20:03 ` [PATCH 6/6] ARM: Add relocatable binary support Sascha Hauer
2013-03-04 20:10   ` Alexander Shiyan
2013-03-04 20:19     ` Sascha Hauer
2013-03-05  4:32       ` Re[2]: " Alexander Shiyan
2013-03-05  7:25         ` Sascha Hauer
2013-03-04 20:53   ` Alexander Aring
2013-03-05 10:46     ` Sascha Hauer

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1362427389-2144-4-git-send-email-s.hauer@pengutronix.de \
    --to=s.hauer@pengutronix.de \
    --cc=barebox@lists.infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox