Even on 64 bit kernel, the mmap failure can happen for a 32 bit task.
Virtual memory space shortage of a task on mmap is reported to userspace
as -ENOMEM. It can be confused as physical memory shortage of overall
system.
The vm_unmapped_area can be called to by some drivers or other kernel
core system like filesystem. In my platform, GPU driver calls to
vm_unmapped_area and the driver returns -ENOMEM even in GPU side
shortage. It can be hard to distinguish which code layer returns the
-ENOMEM.
Create mmap trace file and add trace point of vm_unmapped_area.
i.e.)
265.214275: vm_unmapped_area: addr=fffffffffffffff4 err=-12 tvm=0xffb08 flags=0x1 len=0x100000 lo=0x8000 hi=0xf7182000 mask=0x0 ofs=0x22
265.214276: vm_unmapped_area: addr=fffffffffffffff4 err=-12 tvm=0xffb08 flags=0x0 len=0x100000 lo=0x40000000 hi=0xfffff000 mask=0x0 ofs=0x22
510.827472: vm_unmapped_area: addr=7377060000 err=0 tvm=0x262f flags=0x1 len=0x7f000 lo=0x8000 hi=0x73795f7000 mask=0x0 ofs=0x22
510.827668: vm_unmapped_area: addr=73794d1000 err=0 tvm=0x25cc flags=0x1 len=0x1000 lo=0x8000 hi=0x73795f7000 mask=0x0 ofs=0x22
Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
---
include/trace/events/mmap.h | 52 +++++++++++++++++++++++++++++++++++++++++++++
mm/mmap.c | 12 +++++++++--
2 files changed, 62 insertions(+), 2 deletions(-)
create mode 100644 include/trace/events/mmap.h
diff --git a/include/trace/events/mmap.h b/include/trace/events/mmap.h
new file mode 100644
index 000000000000..a51dd8af6f8c
--- /dev/null
+++ b/include/trace/events/mmap.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mmap
+
+#if !defined(_TRACE_MMAP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MMAP_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(vm_unmapped_area,
+
+ TP_PROTO(unsigned long addr, struct vm_unmapped_area_info *info),
+
+ TP_ARGS(addr, info),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, addr)
+ __field(unsigned long, error)
+ __field(unsigned long, total_vm)
+ __field(unsigned long, flags)
+ __field(unsigned long, length)
+ __field(unsigned long, low_limit)
+ __field(unsigned long, high_limit)
+ __field(unsigned long, align_mask)
+ __field(unsigned long, align_offset)
+ ),
+
+ TP_fast_assign(
+ __entry->addr = addr;
+ if (IS_ERR_VALUE(addr))
+ __entry->error = addr;
+ else
+ __entry->error = 0;
+ __entry->total_vm = current->mm->total_vm;
+ __entry->flags = info->flags;
+ __entry->length = info->length;
+ __entry->low_limit = info->low_limit;
+ __entry->high_limit = info->high_limit;
+ __entry->align_mask = info->align_mask;
+ __entry->align_offset = info->align_offset;
+ ),
+
+ TP_printk("addr=%lx err=%ld tvm=0x%lx flags=0x%lx len=0x%lx lo=0x%lx hi=0x%lx mask=0x%lx ofs=0x%lx\n",
+ __entry->addr, __entry->error, __entry->total_vm,
+ __entry->flags, __entry->length, __entry->low_limit,
+ __entry->high_limit, __entry->align_mask,
+ __entry->align_offset)
+);
+#endif
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/mmap.c b/mm/mmap.c
index eeaddb76286c..68ccbd7d5256 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -53,6 +53,9 @@
#include <asm/tlb.h>
#include <asm/mmu_context.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/mmap.h>
+
#include "internal.h"
#ifndef arch_mmap_check
@@ -2061,10 +2064,15 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
*/
unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
{
+ unsigned long addr;
+
if (info->flags & VM_UNMAPPED_AREA_TOPDOWN)
- return unmapped_area_topdown(info);
+ addr = unmapped_area_topdown(info);
else
- return unmapped_area(info);
+ addr = unmapped_area(info);
+
+ trace_vm_unmapped_area(addr, info);
+ return addr;
}
#ifndef arch_get_mmap_end
--
2.13.7
