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非问题；
该流程是在加载elf时，读取elf段，判断是否可以支持大页加载。从test的elf结构中读到了多个segment，并将多个段起始、结束地址做对齐，最后根据对齐地址判断是否会段重叠，若重叠则不使用大页。

@buaixuebi

问题根因：编译出的elf文件包含多个段，其中两段在做页对齐时，对齐到了同一个页。出现段重叠
问题影响：编译指定的2M大页程序，实际arm是64K页表，只支持512M大页，编译时按2M对齐，实际2个段映射到同一个页；
问题处理：非问题，将Makefile的2M对齐，修改为512M页对齐；

[root@openEuler common]# readelf -l test

Elf file type is EXEC (Executable file)
Entry point 0x2005c0
There are 9 program headers, starting at offset 64

Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000200040 0x0000000000200040
0x00000000000001f8 0x00000000000001f8 R 0x8
INTERP 0x0000000000000238 0x0000000000200238 0x0000000000200238
0x000000000000001b 0x000000000000001b R 0x1
[Requesting program interpreter: /lib/ld-linux-aarch64.so.1]
LOAD 0x0000000000000000 0x0000000000200000 0x0000000000200000
0x00000000000008e0 0x00000000000008e0 R E 0x200000
LOAD 0x00000000001ffdd8 0x00000000005ffdd8 0x00000000005ffdd8
0x0000000000000260 0x0000000000000268 RW 0x200000
DYNAMIC 0x00000000001ffde8 0x00000000005ffde8 0x00000000005ffde8
0x00000000000001e0 0x00000000000001e0 RW 0x8
NOTE 0x0000000000000254 0x0000000000200254 0x0000000000200254
0x0000000000000044 0x0000000000000044 R 0x4
GNU_EH_FRAME 0x00000000000007ac 0x00000000002007ac 0x00000000002007ac
0x0000000000000044 0x0000000000000044 R 0x4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 0x10
GNU_RELRO 0x00000000001ffdd8 0x00000000005ffdd8 0x00000000005ffdd8
0x0000000000000228 0x0000000000000228 R 0x1

export HUGETLB_ELFMAP='R:W';export LD_LIBRARY_PATH='./;export HUGETLB_VERBOSE=3;export HUGETLB_SHARE=1

Starting program: /opt/ETS/testcases/bin/package_test/libhugetlbfs/common/test
libhugetlbfs: INFO: Found pagesize 524288 kB
libhugetlbfs: INFO: Parsed kernel version: [4] . [19] . [90]
libhugetlbfs: INFO: Feature private_reservations is present in this kernel
libhugetlbfs: INFO: Feature noreserve_safe is present in this kernel
libhugetlbfs: INFO: Feature map_hugetlb is present in this kernel
libhugetlbfs: INFO: Kernel has MAP_PRIVATE reservations. Disabling heap prefaulting.
libhugetlbfs: INFO: Kernel supports MAP_HUGETLB
libhugetlbfs: INFO: HUGETLB_SHARE=1, sharing enabled for only read-only segments
libhugetlbfs: INFO: HUGETLB_NO_RESERVE=no, reservations enabled
libhugetlbfs: INFO: Segment 0 (phdr 2): 0x200000-0x2008e0 (filesz=0x8e0) (prot = 0x5)

Breakpoint 2, parse_elf_normal (info=0xfffffffff2f8, size=64, data=0x0) at elflink.c:742
742 segments[num_segs].page_size = seg_psize;
(gdb) p i
$15 = 2
(gdb) p info->dlpi_phdr[2]
$16 = {p_type = 1, p_flags = 5, p_offset = 0, p_vaddr = 2097152, p_paddr = 2097152, p_filesz = 2272, p_memsz = 2272, p_align = 2097152}
(gdb) p /x info->dlpi_phdr[2]
$17 = {p_type = 0x1, p_flags = 0x5, p_offset = 0x0, p_vaddr = 0x200000, p_paddr = 0x200000, p_filesz = 0x8e0, p_memsz = 0x8e0, p_align = 0x200000}
(gdb) c
Continuing.
libhugetlbfs: INFO: Segment 1 (phdr 3): 0x5ffdd8-0x600040 (filesz=0x260) (prot = 0x3)

Breakpoint 2, parse_elf_normal (info=0xfffffffff2f8, size=64, data=0x0) at elflink.c:742
742 segments[num_segs].page_size = seg_psize;
(gdb) c
Continuing.

Breakpoint 1, verify_segment_layout (segs=0xfffffffff198, num_segs=2) at elflink.c:654
654 long base_size = getpagesize();
(gdb) bt
#0 verify_segment_layout (segs=0xfffffffff198, num_segs=2) at elflink.c:654
#1 0x0000fffff7f54e3c in parse_elf_normal (info=0xfffffffff2f8, size=64, data=0x0) at elflink.c:747
#2 0x0000fffff7edf870 in dl_iterate_phdr () from /lib64/libc.so.6
#3 0x0000fffff7f576c4 in parse_elf () at elflink.c:1292
#4 0x0000fffff7f577c4 in __lh_hugetlbfs_setup_elflink () at elflink.c:1309
#5 0x0000fffff7f5c08c in setup_libhugetlbfs () at init.c:36
#6 0x0000fffff7fcd584 in ?? () from /lib/ld-linux-aarch64.so.1
#7 0x0000fffff7fcd688 in ?? () from /lib/ld-linux-aarch64.so.1
#8 0x0000fffff7fc1204 in ?? () from /lib/ld-linux-aarch64.so.1
Backtrace stopped: not enough registers or memory available to unwind further
(gdb) f 1
#1 0x0000fffff7f54e3c in parse_elf_normal (info=0xfffffffff2f8, size=64, data=0x0) at elflink.c:747
747 if (verify_segment_layout(segments, num_segs))
(gdb) p /x info->dlpi_phdr[2]
$18 = {p_type = 0x1, p_flags = 0x5, p_offset = 0x0, p_vaddr = 0x200000, p_paddr = 0x200000, p_filesz = 0x8e0, p_memsz = 0x8e0, p_align = 0x200000}
(gdb) p /x segments[0]
$19 = {start = 0x0, end = 0x20000000, page_size = 0x20000000}
(gdb) p /x info->dlpi_phdr[3]
$20 = {p_type = 0x1, p_flags = 0x6, p_offset = 0x1ffdd8, p_vaddr = 0x5ffdd8, p_paddr = 0x5ffdd8, p_filesz = 0x260, p_memsz = 0x268, p_align = 0x200000}
(gdb) p /x segments[1]
$21 = {start = 0x0, end = 0x20000000, page_size = 0x20000000}
(gdb) p /x info ->dlpi_addr
$22 = 0x0
(gdb) p /x seg_psize
$23 = 0x20000000

将Makefile修改为按512M对齐后，无段重叠的问题
$(CC) -g test.c -o test -Wl,-zcommon-page-size=0x20000000 -Wl,-zmax-page-size=0x20000000 -Wl,-Ttext-segment=0x20000000 -lhugetlbfs

[root@openEuler 2m]# readelf -l test

Elf file type is EXEC (Executable file)
Entry point 0x200005c0
There are 9 program headers, starting at offset 64

Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000020000040 0x0000000020000040
0x00000000000001f8 0x00000000000001f8 R 0x8
INTERP 0x0000000000000238 0x0000000020000238 0x0000000020000238
0x000000000000001b 0x000000000000001b R 0x1
[Requesting program interpreter: /lib/ld-linux-aarch64.so.1]
LOAD 0x0000000000000000 0x0000000020000000 0x0000000020000000
0x00000000000008e0 0x00000000000008e0 R E 0x20000000
LOAD 0x000000001ffffdd8 0x000000005ffffdd8 0x000000005ffffdd8
0x0000000000000260 0x0000000000000268 RW 0x20000000
DYNAMIC 0x000000001ffffde8 0x000000005ffffde8 0x000000005ffffde8
0x00000000000001e0 0x00000000000001e0 RW 0x8
NOTE 0x0000000000000254 0x0000000020000254 0x0000000020000254
0x0000000000000044 0x0000000000000044 R 0x4
GNU_EH_FRAME 0x00000000000007ac 0x00000000200007ac 0x00000000200007ac
0x0000000000000044 0x0000000000000044 R 0x4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 0x10
GNU_RELRO 0x000000001ffffdd8 0x000000005ffffdd8 0x000000005ffffdd8
0x0000000000000228 0x0000000000000228 R 0x1

[root@openEuler 2m]# ./test
libhugetlbfs: INFO: Found pagesize 524288 kB
libhugetlbfs: INFO: Parsed kernel version: [4] . [19] . [90]
libhugetlbfs: INFO: Feature private_reservations is present in this kernel
libhugetlbfs: INFO: Feature noreserve_safe is present in this kernel
libhugetlbfs: INFO: Feature map_hugetlb is present in this kernel
libhugetlbfs: INFO: Kernel has MAP_PRIVATE reservations. Disabling heap prefaulting.
libhugetlbfs: INFO: Kernel supports MAP_HUGETLB
libhugetlbfs: WARNING: Hugepage size 536870912 unavailablelibhugetlbfs: WARNING: Hugepage size 536870912 unavailablelibhugetlbfs: INFO: HUGETLB_SHARE=1, sharing enabled for only read-only segments
libhugetlbfs: INFO: HUGETLB_NO_RESERVE=no, reservations enabled
libhugetlbfs: INFO: No segments were appropriate for remapping
Hello WorldHello WorldHello World[root@openEuler 2m]#

@buaixuebi @Charlie_Li pls check

@吴旭
改成512对齐后 有什么影响吗？

@吴旭
改成512对齐后 有什么影响吗？

@Charlie_Li 没影响，arm 64k页表，只支持512M大页

OK

2M的话设置一下这个 export HUGETLB_DEFAULT_PAGE_SIZE=2048kB