Re: Build breakage due to latest ARM fixes

Russell King - ARM Linux
2013-08-03T00:48:45Z

On Sat, Aug 03, 2013 at 01:41:11AM +0100, Russell King - ARM Linux wrote:
> On Fri, Aug 02, 2013 at 05:24:21PM -0700, Olof Johansson wrote:
> > On Fri, Aug 2, 2013 at 5:07 PM, Russell King - ARM Linux
> > <linux@arm.linux.org.uk> wrote:
> > > On Fri, Aug 02, 2013 at 04:41:11PM -0700, Olof Johansson wrote:
> > >> Russell,
> > >>
> > >> Looks like you sent up some fixes to Linus that broke one of the atmel
> > >> configs (CONFIG_MMU=n):
> > >>
> > >> commit 48be69a026b2c1 ARM: move signal handlers into a vdso-like page
> > >>
> > >> seems to have caused it:
> > >>
> > >> arch/arm/kernel/signal.c: In function 'setup_return':
> > >> arch/arm/kernel/signal.c:413:25: error: 'mm_context_t' has no member
> > >> named 'sigpage'
> > >>
> > >> I see it with at91x40_defconfig.
> > >
> > > I'll look into that. Obviously, I never build nommu because it isn't
> > > part of the build system and the nommu platform I do have - OKI67001 -
> > > doesn't have mainline kernel support. (And if it did, it would not be
> > > DT, so I doubt it's submittable.)
> >
> > I just noticed a whole bunch of boot/runtime failures too across the board too.
> >
> > tegra2 seaboard, exynos arndale, ux500 snowball all panicked. Panda,
> > cubox and sama5 were the only systems that stayed up. Note that I
> > don't do much with them per boot though, so with more runtime they
> > might have hit something too.
> >
> > Some of the oopses below, they're probably not very useful though. Let
> > me know if I can help collect data in any way.
>
> Gah, it looks like I didn't commit an update to these patches.

Okay, this should fix it - *untested* though because of the fscking time
it is here again. The problem is that install_special_mapping() assumes
that the pointer to the pages will be persistent, and it wasn't. I found
that during testing and thought I'd merged the patches in, but I seem to
have totally destroyed the original fixes for this.

arch/arm/kernel/process.c | 9 +++++----
arch/arm/kernel/signal.c | 41 +++++++++++++++++++----------------------
2 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 16ed3f7..536c85f 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -474,17 +474,18 @@ const char *arch_vma_name(struct vm_area_struct *vma)
"[sigpage]" : NULL;
}

+static struct page *signal_page;
extern struct page *get_signal_page(void);

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
struct mm_struct *mm = current->mm;
- struct page *page;
unsigned long addr;
int ret;

- page = get_signal_page();
- if (!page)
+ if (!signal_page)
+ signal_page = get_signal_page();
+ if (!signal_page)
return -ENOMEM;

down_write(&mm->mmap_sem);
@@ -496,7 +497,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

ret = install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
- &page);
+ &signal_page);

if (ret == 0)
mm->context.sigpage = addr;
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 0f17e06..39e7105 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -614,35 +614,32 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
return 0;
}

-static struct page *signal_page;
-
struct page *get_signal_page(void)
{
- if (!signal_page) {
- unsigned long ptr;
- unsigned offset;
- void *addr;
+ unsigned long ptr;
+ unsigned offset;
+ struct page *page;
+ void *addr;

- signal_page = alloc_pages(GFP_KERNEL, 0);
+ page = alloc_pages(GFP_KERNEL, 0);

- if (!signal_page)
- return NULL;
+ if (!page)
+ return NULL;

- addr = page_address(signal_page);
+ addr = page_address(page);

- /* Give the signal return code some randomness */
- offset = 0x200 + (get_random_int() & 0x7fc);
- signal_return_offset = offset;
+ /* Give the signal return code some randomness */
+ offset = 0x200 + (get_random_int() & 0x7fc);
+ signal_return_offset = offset;

- /*
- * Copy signal return handlers into the vector page, and
- * set sigreturn to be a pointer to these.
- */
- memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
+ /*
+ * Copy signal return handlers into the vector page, and
+ * set sigreturn to be a pointer to these.
+ */
+ memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));

- ptr = (unsigned long)addr + offset;
- flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
- }
+ ptr = (unsigned long)addr + offset;
+ flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));

- return signal_page;
+ return page;
}