kernel.git/arch/alpha/mm/fault.c, branch linux-3.16.y

alpha: fix page fault handling for r16-r18 targets

2019-05-02T20:41:51Z

commit 491af60ffb848b59e82f7c9145833222e0bf27a5 upstream. Fix page fault handling code to fixup r16-r18 registers. Before the patch code had off-by-two registers bug. This bug caused overwriting of ps,pc,gp registers instead of fixing intended r16,r17,r18 (see `struct pt_regs`). More details: Initially Dmitry noticed a kernel bug as a failure on strace test suite. Test passes unmapped userspace pointer to io_submit: ```c #include #include #include #include int main(void) { unsigned long ctx = 0; if (syscall(__NR_io_setup, 1, &ctx)) err(1, "io_setup"); const size_t page_size = sysconf(_SC_PAGESIZE); const size_t size = page_size * 2; void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (MAP_FAILED == ptr) err(1, "mmap(%zu)", size); if (munmap(ptr, size)) err(1, "munmap"); syscall(__NR_io_submit, ctx, 1, ptr + page_size); syscall(__NR_io_destroy, ctx); return 0; } ``` Running this test causes kernel to crash when handling page fault: ``` Unable to handle kernel paging request at virtual address ffffffffffff9468 CPU 3 aio(26027): Oops 0 pc = [] ra = [] ps = 0000 Not tainted pc is at sys_io_submit+0x108/0x200 ra is at sys_io_submit+0x6c/0x200 v0 = fffffc00c58e6300 t0 = fffffffffffffff2 t1 = 000002000025e000 t2 = fffffc01f159fef8 t3 = fffffc0001009640 t4 = fffffc0000e0f6e0 t5 = 0000020001002e9e t6 = 4c41564e49452031 t7 = fffffc01f159c000 s0 = 0000000000000002 s1 = 000002000025e000 s2 = 0000000000000000 s3 = 0000000000000000 s4 = 0000000000000000 s5 = fffffffffffffff2 s6 = fffffc00c58e6300 a0 = fffffc00c58e6300 a1 = 0000000000000000 a2 = 000002000025e000 a3 = 00000200001ac260 a4 = 00000200001ac1e8 a5 = 0000000000000001 t8 = 0000000000000008 t9 = 000000011f8bce30 t10= 00000200001ac440 t11= 0000000000000000 pv = fffffc00006fd320 at = 0000000000000000 gp = 0000000000000000 sp = 00000000265fd174 Disabling lock debugging due to kernel taint Trace: [] entSys+0xa4/0xc0 ``` Here `gp` has invalid value. `gp is s overwritten by a fixup for the following page fault handler in `io_submit` syscall handler: ``` __se_sys_io_submit ... ldq a1,0(t1) bne t0,4280 <__se_sys_io_submit+0x180> ``` After a page fault `t0` should contain -EFALUT and `a1` is 0. Instead `gp` was overwritten in place of `a1`. This happens due to a off-by-two bug in `dpf_reg()` for `r16-r18` (aka `a0-a2`). I think the bug went unnoticed for a long time as `gp` is one of scratch registers. Any kernel function call would re-calculate `gp`. Dmitry tracked down the bug origin back to 2.1.32 kernel version where trap_a{0,1,2} fields were inserted into struct pt_regs. And even before that `dpf_reg()` contained off-by-one error. Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: linux-alpha@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reported-and-reviewed-by: "Dmitry V. Levin" Bug: https://bugs.gentoo.org/672040 Signed-off-by: Sergei Trofimovich Signed-off-by: Matt Turner Signed-off-by: Ben Hutchings

vm: add VM_FAULT_SIGSEGV handling support

2015-02-04T10:58:27Z

commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream. The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d4514 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai Tested-by: Jan Engelhardt Acked-by: Heiko Carstens # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds [ luis: backported to 3.16: - file renamed: arch/powerpc/mm/copro_fault.c -> arch/powerpc/platforms/cell/spu_fault.c - dropped changes to arch/nios2/mm/fault.c ] Signed-off-by: Luis Henriques

arch: mm: pass userspace fault flag to generic fault handler

2013-09-12T22:38:01Z

Unlike global OOM handling, memory cgroup code will invoke the OOM killer in any OOM situation because it has no way of telling faults occuring in kernel context - which could be handled more gracefully - from user-triggered faults. Pass a flag that identifies faults originating in user space from the architecture-specific fault handlers to generic code so that memcg OOM handling can be improved. Signed-off-by: Johannes Weiner Reviewed-by: Michal Hocko Cc: David Rientjes Cc: KAMEZAWA Hiroyuki Cc: azurIt Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

alpha/mm/fault.c: Port OOM changes to do_page_fault

2012-08-19T15:41:19Z

Commit d065bd810b6d ("mm: retry page fault when blocking on disk transfer") and 37b23e0525d3 ("x86,mm: make pagefault killable") introduced changes into the x86 pagefault handler for making the page fault handler retryable as well as killable. These changes reduce the mmap_sem hold time, which is crucial during OOM killer invocation. Port these changes to ALPHA. Signed-off-by: Mohd. Faris Signed-off-by: Kautuk Consul Acked-by: Matt Turner Signed-off-by: Michael Cree Signed-off-by: Linus Torvalds

Disintegrate asm/system.h for Alpha

2012-03-28T17:11:12Z

Disintegrate asm/system.h for Alpha. Signed-off-by: David Howells cc: linux-alpha@vger.kernel.org

alpha: invoke oom-killer from page fault

2010-05-25T22:40:28Z

As explained in commit 1c0fe6e3bd, we want to call the architecture independent oom killer when getting an unexplained OOM from handle_mm_fault, rather than simply killing current. [mattst88: kill now unused 'survive' label] Cc: linux-alpha@vger.kernel.org Cc: Richard Henderson Cc: linux-arch@vger.kernel.org Acked-by: David Rientjes Signed-off-by: Matt Turner Signed-off-by: Nick Piggin

Move FAULT_FLAG_xyz into handle_mm_fault() callers

2009-06-21T20:08:22Z

This allows the callers to now pass down the full set of FAULT_FLAG_xyz flags to handle_mm_fault(). All callers have been (mechanically) converted to the new calling convention, there's almost certainly room for architectures to clean up their code and then add FAULT_FLAG_RETRY when that support is added. Signed-off-by: Linus Torvalds

Use helpers to obtain task pid in printks (arch code)

2007-10-19T18:53:43Z

One of the easiest things to isolate is the pid printed in kernel log. There was a patch, that made this for arch-independent code, this one makes so for arch/xxx files. It took some time to cross-compile it, but hopefully these are all the printks in arch code. Signed-off-by: Alexey Dobriyan Signed-off-by: Pavel Emelyanov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

pid namespaces: define is_global_init() and is_container_init()

2007-10-19T18:53:37Z

is_init() is an ambiguous name for the pid==1 check. Split it into is_global_init() and is_container_init(). A cgroup init has it's tsk->pid == 1. A global init also has it's tsk->pid == 1 and it's active pid namespace is the init_pid_ns. But rather than check the active pid namespace, compare the task structure with 'init_pid_ns.child_reaper', which is initialized during boot to the /sbin/init process and never changes. Changelog: 2.6.22-rc4-mm2-pidns1: - Use 'init_pid_ns.child_reaper' to determine if a given task is the global init (/sbin/init) process. This would improve performance and remove dependence on the task_pid(). 2.6.21-mm2-pidns2: - [Sukadev Bhattiprolu] Changed is_container_init() calls in {powerpc, ppc,avr32}/traps.c for the _exception() call to is_global_init(). This way, we kill only the cgroup if the cgroup's init has a bug rather than force a kernel panic. [akpm@linux-foundation.org: fix comment] [sukadev@us.ibm.com: Use is_global_init() in arch/m32r/mm/fault.c] [bunk@stusta.de: kernel/pid.c: remove unused exports] [sukadev@us.ibm.com: Fix capability.c to work with threaded init] Signed-off-by: Serge E. Hallyn Signed-off-by: Sukadev Bhattiprolu Acked-by: Pavel Emelianov Cc: Eric W. Biederman Cc: Cedric Le Goater Cc: Dave Hansen Cc: Herbert Poetzel Cc: Kirill Korotaev Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

During VM oom condition, kill all threads in process group

2007-10-16T16:42:52Z

We have had complaints where a threaded application is left in a bad state after one of it's threads is killed when we hit a VM: out_of_memory condition. Killing just one of the process threads can leave the application in a bad state, whereas killing the entire process group would allow for the application to restart, or be otherwise handled, and makes it very obvious that something has gone wrong. This change allows the entire process group to be taken down, rather than just the one thread. Signed-off-by: Will Schmidt Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Russell King Cc: Ian Molton Cc: Haavard Skinnemoen Cc: Mikael Starvik Cc: David Howells Cc: Andi Kleen Cc: "Luck, Tony" Cc: Hirokazu Takata Cc: Geert Uytterhoeven Cc: Roman Zippel Cc: Ralf Baechle Cc: Kyle McMartin Cc: Matthew Wilcox Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Heiko Carstens Cc: Martin Schwidefsky Cc: Paul Mundt Cc: Kazumoto Kojima Cc: Richard Curnow Cc: William Lee Irwin III Cc: "David S. Miller" Cc: Chris Zankel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds