From a3010a0465383300f909f62b8a83f83ffa7b2517 Mon Sep 17 00:00:00 2001
From: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Date: Wed, 19 Dec 2018 19:16:16 +0300
Subject: ARC: adjust memblock_reserve of kernel memory
In setup_arch_memory we reserve the memory area wherein the kernel
is located. Current implementation may reserve more memory than
it actually required in case of CONFIG_LINUX_LINK_BASE is not
equal to CONFIG_LINUX_RAM_BASE. This happens because we calculate
start of the reserved region relatively to the CONFIG_LINUX_RAM_BASE
and end of the region relatively to the CONFIG_LINUX_RAM_BASE.
For example in case of HSDK board we wasted 256MiB of physical memory:
------------------->8------------------------------
Memory: 770416K/1048576K available (5496K kernel code,
240K rwdata, 1064K rodata, 2200K init, 275K bss,
278160K reserved, 0K cma-reserved)
------------------->8------------------------------
Fix that.
Fixes: 9ed68785f7f2b ("ARC: mm: Decouple RAM base address from kernel link addr")
Cc: stable@vger.kernel.org #4.14+
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/mm/init.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
(limited to 'arch/arc/mm')
diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 43bf4c3a1290..e1ab2d7f1d64 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -119,7 +119,8 @@ void __init setup_arch_memory(void)
*/
memblock_add_node(low_mem_start, low_mem_sz, 0);
- memblock_reserve(low_mem_start, __pa(_end) - low_mem_start);
+ memblock_reserve(CONFIG_LINUX_LINK_BASE,
+ __pa(_end) - CONFIG_LINUX_LINK_BASE);
#ifdef CONFIG_BLK_DEV_INITRD
if (phys_initrd_size) {
--
cgit v1.2.3
From 4d447455e73b47c43dd35fcc38ed823d3182a474 Mon Sep 17 00:00:00 2001
From: Vineet Gupta <vgupta@synopsys.com>
Date: Mon, 10 Dec 2018 16:56:45 -0800
Subject: ARC: mm: do_page_fault fixes #1: relinquish mmap_sem if signal
arrives while handle_mm_fault
do_page_fault() forgot to relinquish mmap_sem if a signal came while
handling handle_mm_fault() - due to say a ctl+c or oom etc.
This would later cause a deadlock by acquiring it twice.
This came to light when running libc testsuite tst-tls3-malloc test but
is likely also the cause for prior seen LTP failures. Using lockdep
clearly showed what the issue was.
| # while true; do ./tst-tls3-malloc ; done
| Didn't expect signal from child: got `Segmentation fault'
| ^C
| ============================================
| WARNING: possible recursive locking detected
| 4.17.0+ #25 Not tainted
| --------------------------------------------
| tst-tls3-malloc/510 is trying to acquire lock:
| 606c7728 (&mm->mmap_sem){++++}, at: __might_fault+0x28/0x5c
|
|but task is already holding lock:
|606c7728 (&mm->mmap_sem){++++}, at: do_page_fault+0x9c/0x2a0
|
| other info that might help us debug this:
| Possible unsafe locking scenario:
|
| CPU0
| ----
| lock(&mm->mmap_sem);
| lock(&mm->mmap_sem);
|
| *** DEADLOCK ***
|
------------------------------------------------------------
What the change does is not obvious (note to myself)
prior code was
| do_page_fault
|
| down_read() <-- lock taken
| handle_mm_fault <-- signal pending as this runs
| if fatal_signal_pending
| if VM_FAULT_ERROR
| up_read
| if user_mode
| return <-- lock still held, this was the BUG
New code
| do_page_fault
|
| down_read() <-- lock taken
| handle_mm_fault <-- signal pending as this runs
| if fatal_signal_pending
| if VM_FAULT_RETRY
| return <-- not same case as above, but still OK since
| core mm already relinq lock for FAULT_RETRY
| ...
|
| < Now falls through for bug case above >
|
| up_read() <-- lock relinquished
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/mm/fault.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
(limited to 'arch/arc/mm')
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index a1d723197084..8df1638259f3 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -141,12 +141,17 @@ good_area:
*/
fault = handle_mm_fault(vma, address, flags);
- /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
if (fatal_signal_pending(current)) {
- if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
- up_read(&mm->mmap_sem);
- if (user_mode(regs))
+
+ /*
+ * if fault retry, mmap_sem already relinquished by core mm
+ * so OK to return to user mode (with signal handled first)
+ */
+ if (fault & VM_FAULT_RETRY) {
+ if (!user_mode(regs))
+ goto no_context;
return;
+ }
}
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
--
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