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Message-ID: <c0d81622-aabf-4ad8-85d6-ba324f2a727f@lucifer.local>
Date: Thu, 3 Oct 2024 08:43:32 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Bert Karwatzki <spasswolf@....de>
Cc: "Liam R . Howlett" <Liam.Howlett@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 14/21] mm/mmap: Avoid zeroing vma tree in mmap_region()
On Thu, Oct 03, 2024 at 12:58:51AM +0200, Bert Karwatzki wrote:
> I justed tested the same kernel version with a .config which was created by copying
> the .config from the standard debian kernel, running "make xconfig" and saving.
> I got a crash here, too, but only on the second attempt (this has happend a few (~3)
> times before). I'm not posting the log as it got to long due to the repetion of the
> procedure, also a standard debian kernel does not print the thread id which I guess
> will make the log more confusing.
>
> Bert
Replying here as the dmesg logs kill any thread you post them on sadly.
Could you try this updated version of the patch? Realise there's 1 specific
bit of information we need :)
Much appreciated as usual!
----8<----
>From e2d37475a47f62e1c21ef2b7ab9432f019c4431b Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Date: Wed, 2 Oct 2024 09:19:28 +0100
Subject: [PATCH] hack: mm: see if we can get some more information 2
Add some dreadful printk() hacks so we can try to get some more information
on what's going on.
---
mm/internal.h | 15 ++++++++++
mm/mmap.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++-
mm/vma.c | 34 ++++++++++++++++++++--
3 files changed, 126 insertions(+), 3 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 93083bbeeefa..cd9414b4651d 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1443,4 +1443,19 @@ static inline void accept_page(struct page *page)
}
#endif /* CONFIG_UNACCEPTED_MEMORY */
+static inline bool check_interesting(unsigned long start, unsigned long end)
+{
+ const unsigned long interesting_start = 0x1740000;
+ /* Include off-by-one on purpose.*/
+ const unsigned long interesting_end = 0x68000000 + 1;
+
+ /* interesting_start interesting_end
+ * |--------------------------|
+ * ============================> end
+ * <============================= start
+ */
+ return end > interesting_start && /* after or overlaps... */
+ start < interesting_end; /* ...overlaps. */
+}
+
#endif /* __MM_INTERNAL_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index dd4b35a25aeb..2a584fc5c937 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1341,6 +1341,18 @@ struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
return vma;
}
+static void ljs_dump(struct mm_struct *mm,
+ unsigned long addr, unsigned long len,
+ vm_flags_t vm_flags, bool is_unmap)
+{
+ if (!check_interesting(addr, addr + len))
+ return;
+
+ pr_err("LJS: %s mm=%p [0x%lx, 0x%lx) [vm_flags=%lu]\n",
+ is_unmap ? "munmap" : "mmap", mm, addr, addr + len,
+ vm_flags);
+}
+
/* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls.
* @mm: The mm_struct
* @start: The start address to munmap
@@ -1354,6 +1366,8 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
{
VMA_ITERATOR(vmi, mm, start);
+ ljs_dump(mm, start, len, 0, true);
+
return do_vmi_munmap(&vmi, mm, start, len, uf, false);
}
@@ -1375,6 +1389,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
VMA_ITERATOR(vmi, mm, addr);
VMG_STATE(vmg, mm, &vmi, addr, end, vm_flags, pgoff);
+ ljs_dump(mm, addr, len, vm_flags, false);
+
vmg.file = file;
/* Find the first overlapping VMA */
vma = vma_find(&vmi, end);
@@ -1390,6 +1406,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vmg.next = vms.next;
vmg.prev = vms.prev;
+
+ if (check_interesting(addr, addr + len))
+ pr_err("LJS: prev=[%lx, %lx), next=[%lx, %lx)\n",
+ vmg.prev ? vmg.prev->vm_start : 0, vmg.prev ? vmg.prev->vm_end : 0,
+ vmg.next ? vmg.next->vm_start : 0, vmg.next ? vmg.next->vm_end : 0);
+
vma = NULL;
} else {
vmg.next = vma_iter_next_rewind(&vmi, &vmg.prev);
@@ -1413,9 +1435,32 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vmg.flags = vm_flags;
}
+ if (check_interesting(addr, addr + len)) {
+ char *special = vm_flags & VM_SPECIAL ? "special" : "";
+ char *has_file = file ? "file-backed" : "";
+
+ pr_err("LJS: Interesting [%lx, %lx) flags=%lu, special=[%s] file=[%s] addr=%lx end=%lx\n",
+ addr, addr+len, vm_flags, special, has_file,
+ vma_iter_addr(&vmi), vma_iter_end(&vmi));
+ }
+
vma = vma_merge_new_range(&vmg);
- if (vma)
+ if (vma) {
+ if (check_interesting(addr, addr + len)) {
+ pr_err("LJS: Merged to [%lx, %lx), addr=%lx, end=%lx\n",
+ vma->vm_start, vma->vm_end, vma_iter_addr(&vmi),
+ vma_iter_end(&vmi));
+
+ mt_validate(&mm->mm_mt);
+
+ pr_err("LJS: Post-validate.\n");
+ }
+
goto expanded;
+ } else if (check_interesting(addr, addr + len)) {
+ pr_err("LJS: Failed to merge [%lx, %lx), reset...\n",
+ addr, addr + len);
+ }
/*
* Determine the object being mapped and call the appropriate
* specific mapper. the address has already been validated, but
@@ -1441,6 +1486,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
if (error)
goto unmap_and_free_vma;
+ if (check_interesting(addr, addr + len)) {
+ pr_err("LJS: call_mmap() on [%lx, %lx) old_flags=%lu new_flags=%lu new range=[%lx, %lx)\n",
+ addr, addr + end, vm_flags, vma->vm_flags, vma->vm_start, vma->vm_end);
+ }
+
if (vma_is_shared_maywrite(vma)) {
error = mapping_map_writable(file->f_mapping);
if (error)
@@ -1467,6 +1517,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
/* If this fails, state is reset ready for a reattempt. */
merge = vma_merge_new_range(&vmg);
+ if (check_interesting(addr, addr + len))
+ pr_err("LJS: flags changed for [%lx, %lx) from %lu to %lu %s\n",
+ vma->vm_start, vma->vm_end, vm_flags, vma->vm_flags,
+ merge ? "merged" : "");
+
if (merge) {
/*
* ->mmap() can change vma->vm_file and fput
@@ -1510,10 +1565,23 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
/* Lock the VMA since it is modified after insertion into VMA tree */
vma_start_write(vma);
+
+ if (check_interesting(addr, addr + len))
+ pr_err("LJS: mm=%p: iter store addr=%lx, end=%lx, vma=[%lx, %lx)\n",
+ mm, vma_iter_addr(&vmi), vma_iter_end(&vmi), vma->vm_start, vma->vm_end);
+
vma_iter_store(&vmi, vma);
mm->map_count++;
vma_link_file(vma);
+ if (check_interesting(addr, addr + len)) {
+ pr_err("LJS: mm=%p: About to validate [%lx, %lx) addr=%lx, end=%lx\n",
+ mm, vma->vm_start,vma->vm_end, vma_iter_addr(&vmi), vma_iter_end(&vmi));
+
+ mt_validate(&mm->mm_mt);
+ pr_err("LJS: Post-validate.\n");
+ }
+
/*
* vma_merge_new_range() calls khugepaged_enter_vma() too, the below
* call covers the non-merge case.
@@ -1530,6 +1598,14 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
perf_event_mmap(vma);
/* Unmap any existing mapping in the area */
+
+ if (check_interesting(addr, addr + len)) {
+ pr_err("LJS: mm=%p: About to validate [%lx, %lx) addr=%lx, end=%lx\n",
+ mm, vma->vm_start,vma->vm_end, vma_iter_addr(&vmi), vma_iter_end(&vmi));
+ mt_validate(&mm->mm_mt);
+ pr_err("LJS: Post-validate.\n");
+ }
+
vms_complete_munmap_vmas(&vms, &mas_detach);
vm_stat_account(mm, vm_flags, pglen);
@@ -1594,6 +1670,8 @@ static int __vm_munmap(unsigned long start, size_t len, bool unlock)
LIST_HEAD(uf);
VMA_ITERATOR(vmi, mm, start);
+ ljs_dump(mm, start, start + len, 0, true);
+
if (mmap_write_lock_killable(mm))
return -EINTR;
diff --git a/mm/vma.c b/mm/vma.c
index 4737afcb064c..33f80e82704b 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -1108,8 +1108,13 @@ void vms_clean_up_area(struct vma_munmap_struct *vms,
vms_clear_ptes(vms, mas_detach, true);
mas_set(mas_detach, 0);
mas_for_each(mas_detach, vma, ULONG_MAX)
- if (vma->vm_ops && vma->vm_ops->close)
+ if (vma->vm_ops && vma->vm_ops->close) {
+ if (check_interesting(vma->vm_start, vma->vm_end))
+ pr_err("LJS: mm=%p Closing [%lx, %lx)\n",
+ vma->vm_mm, vma->vm_start, vma->vm_end);
+
vma->vm_ops->close(vma);
+ }
vms->closed_vm_ops = true;
}
@@ -1179,6 +1184,10 @@ int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
struct vm_area_struct *next = NULL;
int error;
+ if (check_interesting(vms->vma->vm_start, vms->vma->vm_end))
+ pr_err("LJS2 vms->start=%lx, vms->vma->vm_start=%lx\n",
+ vms->start, vms->vma->vm_start);
+
/*
* If we need to split any vma, do it now to save pain later.
* Does it split the first one?
@@ -1202,6 +1211,11 @@ int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
goto start_split_failed;
}
+ if (check_interesting(vms->vma->vm_start, vms->vma->vm_end))
+ pr_err("LJS: mm=%p vms=[%lx, %lx) split START of [%lx, %lx)\n",
+ vms->vma->vm_mm, vms->start, vms->end,
+ vms->vma->vm_start, vms->vma->vm_end);
+
error = __split_vma(vms->vmi, vms->vma, vms->start, 1);
if (error)
goto start_split_failed;
@@ -1217,12 +1231,23 @@ int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
for_each_vma_range(*(vms->vmi), next, vms->end) {
long nrpages;
+ if (check_interesting(vms->vma->vm_start, vms->vma->vm_end))
+ pr_err("LJS: mm=%p vms=[%lx, %lx) UNMAP [%lx, %lx)\n",
+ vms->vma->vm_mm, vms->start, vms->end,
+ next->vm_start, next->vm_end);
+
if (!can_modify_vma(next)) {
error = -EPERM;
goto modify_vma_failed;
}
/* Does it split the end? */
if (next->vm_end > vms->end) {
+
+ if (check_interesting(next->vm_start, next->vm_end))
+ pr_err("LJS: mm=%p vms=[%lx, %lx) split END of [%lx, %lx)\n",
+ next->vm_mm, vms->start, vms->end,
+ next->vm_start, next->vm_end);
+
error = __split_vma(vms->vmi, next, vms->end, 0);
if (error)
goto end_split_failed;
@@ -1295,9 +1320,14 @@ int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
}
#endif
- while (vma_iter_addr(vms->vmi) > vms->start)
+ while (vma_iter_addr(vms->vmi) > vms->start) {
vma_iter_prev_range(vms->vmi);
+ if (check_interesting(vms->vma->vm_start, vms->vma->vm_end))
+ pr_err("LJS3: addr=%lx, vms->start=%lx\n",
+ vma_iter_addr(vms->vmi), vms->start);
+ }
+
vms->clear_ptes = true;
return 0;
--
2.46.2
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