linux-kernel - [PATCH 03/11] x86/xip: copy writable sections into RAM

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Date:	Mon, 23 Mar 2015 00:46:32 -0700
From:	Jim Kukunas <james.t.kukunas@...ux.intel.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	tom.zanussi@...ux.intel.com
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, tglx@...utronix.de,
	mingo@...hat.com, x86@...nel.org
Subject: [PATCH 03/11] x86/xip: copy writable sections into RAM

Loads all writable and non-zero sections into their VMA.

Signed-off-by: Jim Kukunas <james.t.kukunas@...ux.intel.com>
---
 arch/x86/include/asm/sections.h |  4 ++++
 arch/x86/kernel/head_32.S       | 22 ++++++++++++++++++++++
 arch/x86/kernel/vmlinux.lds.S   |  4 ++++
 3 files changed, 30 insertions(+)

diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 0a52424..9535e95 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -11,4 +11,8 @@ extern struct exception_table_entry __stop___ex_table[];
 extern char __end_rodata_hpage_align[];
 #endif
 
+#ifdef CONFIG_XIP_KERNEL
+extern char phys_sdata[];
+#endif
+
 #endif	/* _ASM_X86_SECTIONS_H */
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index f36bd42..80f344a 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -86,6 +86,28 @@ RESERVE_BRK(pagetables, INIT_MAP_SIZE)
  */
 __HEAD
 ENTRY(startup_32)
+
+#ifdef CONFIG_XIP_KERNEL
+	/*
+	 * Copy writable sections into RAM
+	 */
+
+	movl %esi, %ebp	# Preserve pointer to zero-page
+
+	leal pa(_sdata), %edi
+	leal phys_edata, %ecx
+	leal phys_sdata, %esi
+	subl %esi, %ecx
+
+	cld
+xip_data_cp:
+	lodsb
+	stosb
+	loop xip_data_cp
+
+	movl %ebp, %esi
+#endif
+
 	movl pa(stack_start),%ecx
 	
 	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 414a1ac..59a9edb 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -133,6 +133,9 @@ SECTIONS
 	RO_DATA(PAGE_SIZE)
 	X64_ALIGN_DEBUG_RODATA_END
 
+	phys_sdata = LOADADDR(.data);
+	phys_edata = phys_sdata + (_end_nonzero - _sdata);
+
 	/* Data */
 	.data : AT(ADDR(.data) - LOAD_OFFSET) DATA_ALIGN {
 		/* Start of data section */
@@ -319,6 +322,7 @@ SECTIONS
 		NOSAVE_DATA
 	}
 #endif
+	_end_nonzero = .;
 
 	/* BSS */
 	. = ALIGN(PAGE_SIZE);
-- 
2.1.0

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