The patch titled
i386: distinguish absolute symbols
has been added to the -mm tree. Its filename is
i386-distinguish-absolute-symbols.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: i386: distinguish absolute symbols
From: Vivek Goyal <vgoyal@xxxxxxxxxx>
Ld knows about 2 kinds of symbols, absolute and section relative. Section
relative symbols symbols change value when a section is moved and absolute
symbols do not.
Currently in the linker script we have several labels marking the beginning
and ending of sections that are outside of sections, making them absolute
symbols. Having a mixture of absolute and section relative symbols refereing
to the same data is currently harmless but it is confusing.
This must be done carefully as newer revs of ld do not place symbols that
appear in sections without data and instead ld makes those symbols global :(
My ultimate goal is to build a relocatable kernel. The safest and least
intrusive technique is to generate relocation entries so the kernel can be
relocated at load time. The only penalty would be an increase in the size of
the kernel binary. The problem is that if absolute and relocatable symbols
are not properly specified absolute symbols will be relocated or section
relative symbols won't be, which is fatal.
The practical motivation is that when generating kernels that will run from a
reserved area for analyzing what caused a kernel panic, it is simpler if you
don't need to hard code the physical memory location they will run at,
especially for the distributions.
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
arch/i386/kernel/vmlinux.lds.S | 109 ++++++++++++++--------------
include/asm-generic/vmlinux.lds.h | 10 +-
2 files changed, 63 insertions(+), 56 deletions(-)
diff -puN arch/i386/kernel/vmlinux.lds.S~i386-distinguish-absolute-symbols arch/i386/kernel/vmlinux.lds.S
--- a/arch/i386/kernel/vmlinux.lds.S~i386-distinguish-absolute-symbols
+++ a/arch/i386/kernel/vmlinux.lds.S
@@ -24,33 +24,34 @@ SECTIONS
. = __KERNEL_START;
phys_startup_32 = startup_32 - LOAD_OFFSET;
/* read-only */
- _text = .; /* Text and read-only data */
.text : AT(ADDR(.text) - LOAD_OFFSET) {
+ _text = .; /* Text and read-only data */
*(.text)
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
*(.fixup)
*(.gnu.warning)
- } :text = 0x9090
-
- _etext = .; /* End of text section */
+ _etext = .; /* End of text section */
+ } :text = 0x9090
. = ALIGN(16); /* Exception table */
- __start___ex_table = .;
- __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
- __stop___ex_table = .;
+ __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
+ __start___ex_table = .;
+ *(__ex_table)
+ __stop___ex_table = .;
+ }
_sdata = .; /* End of text section */
RODATA
. = ALIGN(4);
- __tracedata_start = .;
.tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) {
+ __tracedata_start = .;
*(.tracedata)
+ __tracedata_end = .;
}
- __tracedata_end = .;
/* writeable */
.data : AT(ADDR(.data) - LOAD_OFFSET) { /* Data */
@@ -59,10 +60,12 @@ SECTIONS
} :data
. = ALIGN(4096);
- __nosave_begin = .;
- .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) { *(.data.nosave) }
- . = ALIGN(4096);
- __nosave_end = .;
+ .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
+ __nosave_begin = .;
+ *(.data.nosave)
+ . = ALIGN(4096);
+ __nosave_end = .;
+ }
. = ALIGN(4096);
.data.page_aligned : AT(ADDR(.data.page_aligned) - LOAD_OFFSET) {
@@ -76,8 +79,10 @@ SECTIONS
/* rarely changed data like cpu maps */
. = ALIGN(32);
- .data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) { *(.data.read_mostly) }
- _edata = .; /* End of data section */
+ .data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) {
+ *(.data.read_mostly)
+ _edata = .; /* End of data section */
+ }
#ifdef CONFIG_STACK_UNWIND
. = ALIGN(4);
@@ -95,39 +100,41 @@ SECTIONS
/* might get freed after init */
. = ALIGN(4096);
- __smp_alt_begin = .;
- __smp_alt_instructions = .;
.smp_altinstructions : AT(ADDR(.smp_altinstructions) - LOAD_OFFSET) {
+ __smp_alt_begin = .;
+ __smp_alt_instructions = .;
*(.smp_altinstructions)
+ __smp_alt_instructions_end = .;
}
- __smp_alt_instructions_end = .;
. = ALIGN(4);
- __smp_locks = .;
.smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
+ __smp_locks = .;
*(.smp_locks)
+ __smp_locks_end = .;
}
- __smp_locks_end = .;
.smp_altinstr_replacement : AT(ADDR(.smp_altinstr_replacement) - LOAD_OFFSET) {
*(.smp_altinstr_replacement)
+ . = ALIGN(4096);
+ __smp_alt_end = .;
}
- . = ALIGN(4096);
- __smp_alt_end = .;
/* will be freed after init */
. = ALIGN(4096); /* Init code and data */
- __init_begin = .;
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
+ __init_begin = .;
_sinittext = .;
*(.init.text)
_einittext = .;
}
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) { *(.init.data) }
. = ALIGN(16);
- __setup_start = .;
- .init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) { *(.init.setup) }
- __setup_end = .;
- __initcall_start = .;
+ .init.setup : AT(ADDR(.init.setup) - LOAD_OFFSET) {
+ __setup_start = .;
+ *(.init.setup)
+ __setup_end = .;
+ }
.initcall.init : AT(ADDR(.initcall.init) - LOAD_OFFSET) {
+ __initcall_start = .;
*(.initcall1.init)
*(.initcall2.init)
*(.initcall3.init)
@@ -135,20 +142,20 @@ SECTIONS
*(.initcall5.init)
*(.initcall6.init)
*(.initcall7.init)
+ __initcall_end = .;
}
- __initcall_end = .;
- __con_initcall_start = .;
.con_initcall.init : AT(ADDR(.con_initcall.init) - LOAD_OFFSET) {
+ __con_initcall_start = .;
*(.con_initcall.init)
+ __con_initcall_end = .;
}
- __con_initcall_end = .;
SECURITY_INIT
. = ALIGN(4);
- __alt_instructions = .;
.altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
+ __alt_instructions = .;
*(.altinstructions)
+ __alt_instructions_end = .;
}
- __alt_instructions_end = .;
.altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
*(.altinstr_replacement)
}
@@ -157,32 +164,32 @@ SECTIONS
.exit.text : AT(ADDR(.exit.text) - LOAD_OFFSET) { *(.exit.text) }
.exit.data : AT(ADDR(.exit.data) - LOAD_OFFSET) { *(.exit.data) }
. = ALIGN(4096);
- __initramfs_start = .;
- .init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) { *(.init.ramfs) }
- __initramfs_end = .;
+ .init.ramfs : AT(ADDR(.init.ramfs) - LOAD_OFFSET) {
+ __initramfs_start = .;
+ *(.init.ramfs)
+ __initramfs_end = .;
+ }
. = ALIGN(L1_CACHE_BYTES);
- __per_cpu_start = .;
- .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { *(.data.percpu) }
- __per_cpu_end = .;
+ .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) {
+ __per_cpu_start = .;
+ *(.data.percpu)
+ __per_cpu_end = .;
+ }
. = ALIGN(4096);
- __init_end = .;
/* freed after init ends here */
- __bss_start = .; /* BSS */
- .bss.page_aligned : AT(ADDR(.bss.page_aligned) - LOAD_OFFSET) {
- *(.bss.page_aligned)
- }
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
+ __init_end = .;
+ __bss_start = .; /* BSS */
+ *(.bss.page_aligned)
*(.bss)
+ . = ALIGN(4);
+ __bss_stop = .;
+ _end = . ;
+ /* This is where the kernel creates the early boot page tables */
+ . = ALIGN(4096);
+ pg0 = . ;
}
- . = ALIGN(4);
- __bss_stop = .;
-
- _end = . ;
-
- /* This is where the kernel creates the early boot page tables */
- . = ALIGN(4096);
- pg0 = .;
/* Sections to be discarded */
/DISCARD/ : {
diff -puN include/asm-generic/vmlinux.lds.h~i386-distinguish-absolute-symbols include/asm-generic/vmlinux.lds.h
--- a/include/asm-generic/vmlinux.lds.h~i386-distinguish-absolute-symbols
+++ a/include/asm-generic/vmlinux.lds.h
@@ -11,8 +11,8 @@
#define RODATA \
. = ALIGN(4096); \
- __start_rodata = .; \
.rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start_rodata) = .; \
*(.rodata) *(.rodata.*) \
*(__vermagic) /* Kernel version magic */ \
} \
@@ -119,17 +119,17 @@
*(__ksymtab_strings) \
} \
\
+ /* Unwind data binary search table */ \
+ EH_FRAME_HDR \
+ \
/* Built-in module parameters. */ \
__param : AT(ADDR(__param) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start___param) = .; \
*(__param) \
VMLINUX_SYMBOL(__stop___param) = .; \
+ VMLINUX_SYMBOL(__end_rodata) = .; \
} \
\
- /* Unwind data binary search table */ \
- EH_FRAME_HDR \
- \
- __end_rodata = .; \
. = ALIGN(4096);
#define SECURITY_INIT \
_
Patches currently in -mm which might be from vgoyal@xxxxxxxxxx are
i386-distinguish-absolute-symbols.patch
i386-remove-unnecessary-align-in-vmlinuxldss.patch
i386-force-data-segment-to-be-4k-aligned.patch
i386-define-__pa_symbol.patch
i386-reserve-kernel-memory-starting-from-_text.patch
i386-config_physical_start-cleanup.patch
i386-kallsyms-generate-relocatable-symbols.patch
i386-relocatable-kernel-support.patch
i386-warn-upon-absolute-relocations-being-present.patch
i386-implement-config_physical_align.patch
i386-extend-bzimage-protocol-for-relocatable-protected-mode-kernel.patch
-
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