From: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx> Subject: mm: mmap: add trace point of vm_unmapped_area 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.) 277.156599: vm_unmapped_area: addr=77e0d03000 err=0 total_vm=0x17014b flags=0x1 len=0x400000 lo=0x8000 hi=0x7878c27000 mask=0x0 ofs=0x1 342.838740: vm_unmapped_area: addr=0 err=-12 total_vm=0xffb08 flags=0x0 len=0x100000 lo=0x40000000 hi=0xfffff000 mask=0x0 ofs=0x22 [akpm@xxxxxxxxxxxxxxxxxxxx: prefix address printk with 0x, per Matthew] Link: http://lkml.kernel.org/r/20200320055823.27089-3-jaewon31.kim@xxxxxxxxxxx Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Michel Lespinasse <walken@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/trace/events/mmap.h | 48 ++++++++++++++++++++++++++++++++++ mm/mmap.c | 12 +++++++- 2 files changed, 58 insertions(+), 2 deletions(-) --- /dev/null +++ a/include/trace/events/mmap.h @@ -0,0 +1,48 @@ +/* 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, 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; + __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=0x%lx err=%ld total_vm=0x%lx flags=0x%lx len=0x%lx lo=0x%lx hi=0x%lx mask=0x%lx ofs=0x%lx\n", + IS_ERR_VALUE(__entry->addr) ? 0 : __entry->addr, + IS_ERR_VALUE(__entry->addr) ? __entry->addr : 0, + __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> --- a/mm/mmap.c~mm-mmap-add-trace-point-of-vm_unmapped_area +++ a/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 @@ found_highest: */ 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 _
