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SubjectRe: 2.6.8-rc2-mm1 link errors
On Wed, 2004-07-28 at 16:49, Andrew Morton wrote:
> Nope. Could you take a look at the code in the top-level
> Makefile which is doing this, work out why it broke?

It seems to come down to this warning:

{standard input}: Assembler messages:
{standard input}:3565: Warning: setting incorrect section type for

Which comes from this code in the 4k stacks code:

static char softirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE), __section__(".bss.page_aligned")));
static char hardirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE), __section__(".bss.page_aligned")));

Removing the __section__() fixes it, as does moving to gcc 3.2 or 3.3,
but gcc 2.95 and 3.0 still exhibit the problem. It seems the 4k stack
developers like newer compilers than I do :)

The gcc 2.95 section declaration looks like this:
.section .bss.page_aligned,"aw",@progbits
while the 3.1 section looks like this:
.section .bss.page_aligned,"aw",@nobits

It's definitely a bug that's been fixed:

I've been told that I can fix it with a carefully crafted assembly file
and maybe a change to the linker script, but all that it buys us is a
little space in the uncompressed kernel image. Plus, the warning will
still be there at compile-time.

I say, put them back in plain old BSS. Patch attached.

-- Dave
diff -rup linux-2.6.8-rc2-mm1/arch/i386/kernel/irq.c linux-2.6.8-rc2-mm1-irqstackbss/arch/i386/kernel/irq.c
--- linux-2.6.8-rc2-mm1/arch/i386/kernel/irq.c 2004-07-28 18:10:40.000000000 -0700
+++ linux-2.6.8-rc2-mm1-irqstackbss/arch/i386/kernel/irq.c 2004-07-28 18:52:41.000000000 -0700
@@ -1118,8 +1118,12 @@ void init_irq_proc (void)

-static char softirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE), __section__(".bss.page_aligned")));
-static char hardirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE), __section__(".bss.page_aligned")));
+ * These should really be __section__(".bss.page_aligned") as well, but
+ * gcc's 3.0 and earlier don't handle that correctly.
+ */
+static char softirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE)));
+static char hardirq_stack[NR_CPUS * THREAD_SIZE] __attribute__((__aligned__(THREAD_SIZE)));

* allocate per-cpu stacks for hardirq and for softirq processing
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