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Date: Tue, 5 May 2009 18:39:30 +0200
From: Sam Ravnborg <sam@...nborg.org>
To: Jan Beulich <jbeulich@...ell.com>
Cc: mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86-64: fix build with older binutils
Hi Jan.
> Impact: build fix
>
> binutils prior to 2.17 can't deal with the currently possible situation
> of a new segment following the per-CPU segment, but that new segment
> being empty - objcopy misplaces the .bss (and perhaps also the .brk)
> sections outside of any segment. However, the current ordering of
> sections really just appears to be the effect of cumulative unrelated
> changes; re-ordering things allows to easily guarantee that the segment
> following the per-CPU one is non-empty, and at once eliminates the need
> for the bogus data.init2 segment.
>
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
I like the way your patch simplies the linker scrip for x86.
We have recently merged the linker scripts for 32 and 64 bit,
and I tried to apply your patch on top of the unified version.
(Applied manually obviously).
With a 64 bit defconfig build I got:
/home/sam/x-tools/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-ld: section .vsyscall_0 [00000000016c6000 -> 00000000016c60e7] overlaps section .init.rodata [00000000016c5a00 -> 00000000016c6348]
make[1]: *** [.tmp_vmlinux1] Error 1
I did not try to build a kernel with your original patch.
Can you spot anything obvious wrong in my patch.
It is on top of x86/kbuild in -tip.
Sam
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 4c85b2e..477fa48 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -46,11 +46,10 @@ PHDRS {
data PT_LOAD FLAGS(7); /* RWE */
#ifdef CONFIG_X86_64
user PT_LOAD FLAGS(7); /* RWE */
- data.init PT_LOAD FLAGS(7); /* RWE */
#ifdef CONFIG_SMP
percpu PT_LOAD FLAGS(7); /* RWE */
#endif
- data.init2 PT_LOAD FLAGS(7); /* RWE */
+ init PT_LOAD FLAGS(7); /* RWE */
#endif
note PT_NOTE FLAGS(0); /* ___ */
}
@@ -103,70 +102,58 @@ SECTIONS
__stop___ex_table = .;
} :text = 0x9090
- RODATA
+ RO_DATA(PAGE_SIZE)
/* Data */
. = ALIGN(PAGE_SIZE);
.data : AT(ADDR(.data) - LOAD_OFFSET) {
- DATA_DATA
- CONSTRUCTORS
-
-#ifdef CONFIG_X86_64
- /* End of data section */
- _edata = .;
-#endif
- } :data
+ /* init_task */
+ . = ALIGN(THREAD_SIZE);
+ *(.data.init_task)
-#ifdef CONFIG_X86_32
- /* 32 bit has nosave before _edata */
- . = ALIGN(PAGE_SIZE);
- .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
- __nosave_begin = .;
- *(.data.nosave)
. = ALIGN(PAGE_SIZE);
- __nosave_end = .;
- }
-#endif
-
- . = ALIGN(PAGE_SIZE);
- .data.page_aligned : AT(ADDR(.data.page_aligned) - LOAD_OFFSET) {
*(.data.page_aligned)
- *(.data.idt)
- }
#ifdef CONFIG_X86_32
- . = ALIGN(32);
+ . = ALIGN(32);
#else
- . = ALIGN(PAGE_SIZE);
- . = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
+ . = ALIGN(CONFIG_X86_L1_CACHE_BYTES);
#endif
- .data.cacheline_aligned :
- AT(ADDR(.data.cacheline_aligned) - LOAD_OFFSET) {
*(.data.cacheline_aligned)
- }
- /* rarely changed data like cpu maps */
+ DATA_DATA
+ CONSTRUCTORS
+
+ /* rarely changed data like cpu maps */
#ifdef CONFIG_X86_32
- . = ALIGN(32);
+ . = ALIGN(32);
#else
- . = ALIGN(CONFIG_X86_INTERNODE_CACHE_BYTES);
+ . = ALIGN(CONFIG_X86_INTERNODE_CACHE_BYTES);
#endif
- .data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) {
*(.data.read_mostly)
-#ifdef CONFIG_X86_32
/* End of data section */
_edata = .;
-#endif
+ } :data
+
+#ifdef CONFIG_X86_32
+ /* 32 bit has nosave before _edata */
+ . = ALIGN(PAGE_SIZE);
+ .data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
+ __nosave_begin = .;
+ *(.data.nosave)
+ . = ALIGN(PAGE_SIZE);
+ __nosave_end = .;
}
+#endif
#ifdef CONFIG_X86_64
#define VSYSCALL_ADDR (-10*1024*1024)
-#define VSYSCALL_PHYS_ADDR ((LOADADDR(.data.read_mostly) + \
- SIZEOF(.data.read_mostly) + 4095) & ~(4095))
-#define VSYSCALL_VIRT_ADDR ((ADDR(.data.read_mostly) + \
- SIZEOF(.data.read_mostly) + 4095) & ~(4095))
+#define VSYSCALL_PHYS_ADDR ((LOADADDR(.data) + \
+ SIZEOF(.data) + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1))
+#define VSYSCALL_VIRT_ADDR ((ADDR(.data) + \
+ SIZEOF(.data) + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1))
#define VLOAD_OFFSET (VSYSCALL_ADDR - VSYSCALL_PHYS_ADDR)
#define VLOAD(x) (ADDR(x) - VLOAD_OFFSET)
@@ -232,35 +219,31 @@ SECTIONS
#endif /* CONFIG_X86_64 */
- /* init_task */
- . = ALIGN(THREAD_SIZE);
- .data.init_task : AT(ADDR(.data.init_task) - LOAD_OFFSET) {
- *(.data.init_task)
+ /* will be freed after init - paired with __init_end */
+ .init.start : AT(ADDR(.init.start) - LOAD_OFFSET) {
+ . = ALIGN(PAGE_SIZE);
+ __init_begin = .;
}
-#ifdef CONFIG_X86_64
- :data.init
-#endif
+#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
/*
- * smp_locks might be freed after init
- * start/end must be page aligned
+ * percpu offsets are zero-based on SMP. PERCPU_VADDR() changes the
+ * output PHDR, so the next output section - .init.text - should
+ * start another segment - init.
*/
. = ALIGN(PAGE_SIZE);
- .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
- __smp_locks = .;
- *(.smp_locks)
- __smp_locks_end = .;
- . = ALIGN(PAGE_SIZE);
- }
+ PERCPU_VADDR(0, :percpu)
+#endif
- /* Init code and data - will be freed after init */
- . = ALIGN(PAGE_SIZE);
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
- __init_begin = .; /* paired with __init_end */
_sinittext = .;
INIT_TEXT
_einittext = .;
}
+#ifdef CONFIG_X86_64
+ :init
+#endif
+
.init.data : AT(ADDR(.init.data) - LOAD_OFFSET) {
INIT_DATA
@@ -331,17 +314,7 @@ SECTIONS
}
#endif
-#if defined(CONFIG_X86_64) && defined(CONFIG_SMP)
- /*
- * percpu offsets are zero-based on SMP. PERCPU_VADDR() changes the
- * output PHDR, so the next output section - __data_nosave - should
- * start another section data.init2. Also, pda should be at the head of
- * percpu area. Preallocate it and define the percpu offset symbol
- * so that it can be accessed as a percpu variable.
- */
- . = ALIGN(PAGE_SIZE);
- PERCPU_VADDR(0, :percpu)
-#else
+#if defined(CONFIG_X86_32) || !defined(CONFIG_SMP)
PERCPU(PAGE_SIZE)
#endif
@@ -352,6 +325,18 @@ SECTIONS
__init_end = .;
}
+ /*
+ * smp_locks might be freed after init
+ * start/end must be page aligned
+ */
+ . = ALIGN(PAGE_SIZE);
+ .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
+ __smp_locks = .;
+ *(.smp_locks)
+ __smp_locks_end = .;
+ . = ALIGN(PAGE_SIZE);
+ }
+
#ifdef CONFIG_X86_64
.data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) {
. = ALIGN(PAGE_SIZE);
@@ -359,8 +344,7 @@ SECTIONS
*(.data.nosave)
. = ALIGN(PAGE_SIZE);
__nosave_end = .;
- } :data.init2
- /* use another section data.init2, see PERCPU_VADDR() above */
+ }
#endif
/* BSS */
--
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