请教：strip是怎么工作的？
这两天碰到一个问题，在用strip来删除符号的时候，文件中的program header的虚拟地址被改动了，而起strip也报告如下错误：BFD: stDYGBBi: section cpu1_percpu_data lma 0x300000 overlaps previous sections
那位大侠知道，给讲一下，谢谢。
strip应该只删除某些符号section吧，program header又不是多余符号，为什么要修改呢？ 补充一下：刚才那个报告的错误应该是一些section的位置不对，如下，section cpu_percpu_data 的起始位置和大小都一样，好像不正常。
Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 00
[ 1] .text PROGBITS 0c010000 010000 0f0000 00AX0 0 65536
[ 2] .data PROGBITS 00200000 100000 100000 00WA0 0 16
[ 3] cpu0_percpu_dataPROGBITS 00300000 200000 010000 00WA0 04
[ 4] cpu1_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
[ 5] cpu2_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
[ 6] cpu3_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
[ 7] cpu4_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
[ 8] cpu5_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
[ 9] cpu6_percpu_dataNOBITS 00300000 210000 010000 00WA0 01
但是这也不应该影响到修改program header吧 是不是与你的编译参数有关系？
strip应该没什么错误阿 我运行strip的时候没有加任何参数。
不管怎样，strip都不应该修改program header吧，现在的结果是
strip之前
<unknown>: 8 0x000000 0x2c000000 0x2c000000 0x00000 0x4000000 RW0x8
strip之后
<unknown>: 8 0x000000 0x37f00000 0x2c000000 0x00000 0x4000000 RW0x8
奇怪吧？ 跟踪了一下strip，发现确实修改了vaddr，但是不知道所以然，谁能解释一下最后一段？
static bfd_boolean
copy_elf_program_header (bfd *ibfd, bfd *obfd)
{
Elf_Internal_Ehdr *iehdr;
struct elf_segment_map *map;
struct elf_segment_map *map_first;
struct elf_segment_map **pointer_to_map;
Elf_Internal_Phdr *segment;
unsigned int i;
unsigned int num_segments;
bfd_boolean phdr_included = FALSE;
bfd_boolean p_paddr_valid;
iehdr = elf_elfheader (ibfd);
map_first = NULL;
pointer_to_map = &map_first;
/* If all the segment p_paddr fields are zero, don't set
map->p_paddr_valid.*/
p_paddr_valid = FALSE;
num_segments = elf_elfheader (ibfd)->e_phnum;
for (i = 0, segment = elf_tdata (ibfd)->phdr;
i < num_segments;
i++, segment++)
if (segment->p_paddr != 0)
{
p_paddr_valid = TRUE;
break;
}
for (i = 0, segment = elf_tdata (ibfd)->phdr;
i < num_segments;
i++, segment++)
{
asection *section;
unsigned int section_count;
bfd_size_type amt;
Elf_Internal_Shdr *this_hdr;
asection *first_section = NULL;
asection *lowest_section = NULL;
/* Compute how many sections are in this segment.*/
for (section = ibfd->sections, section_count = 0;
section != NULL;
section = section->next)
{
this_hdr = &(elf_section_data(section)->this_hdr);
if (ELF_IS_SECTION_IN_SEGMENT_FILE (this_hdr, segment))
{
if (!first_section)
first_section = lowest_section = section;
if (section->lma < lowest_section->lma)
lowest_section = section;
section_count++;
}
}
/* Allocate a segment map big enough to contain
all of the sections we have selected.*/
amt = sizeof (struct elf_segment_map);
if (section_count != 0)
amt += ((bfd_size_type) section_count - 1) * sizeof (asection *);
map = bfd_zalloc (obfd, amt);
if (map == NULL)
return FALSE;
/* Initialize the fields of the output segment map with the
input segment.*/
map->next = NULL;
map->p_type = segment->p_type;
map->p_flags = segment->p_flags;
map->p_flags_valid = 1;
map->p_paddr = segment->p_paddr;
map->p_paddr_valid = p_paddr_valid;
map->p_align = segment->p_align;
map->p_align_valid = 1;
map->p_vaddr_offset = 0;
if (map->p_type == PT_GNU_RELRO)
{
/* The PT_GNU_RELRO segment may contain the first a few
bytes in the .got.plt section even if the whole .got.plt
section isn't in the PT_GNU_RELRO segment.We won't
change the size of the PT_GNU_RELRO segment.*/
map->p_size = segment->p_memsz;
map->p_size_valid = 1;
}
/* Determine if this segment contains the ELF file header
and if it contains the program headers themselves.*/
map->includes_filehdr = (segment->p_offset == 0
&& segment->p_filesz >= iehdr->e_ehsize);
map->includes_phdrs = 0;
if (! phdr_included || segment->p_type != PT_LOAD)
{
map->includes_phdrs =
(segment->p_offset <= (bfd_vma) iehdr->e_phoff
&& (segment->p_offset + segment->p_filesz
>= ((bfd_vma) iehdr->e_phoff
+ iehdr->e_phnum * iehdr->e_phentsize)));
if (segment->p_type == PT_LOAD && map->includes_phdrs)
phdr_included = TRUE;
}
if (map->includes_filehdr && first_section)
/* We need to keep the space used by the headers fixed.*/
map->header_size = first_section->vma - segment->p_vaddr;
if (!map->includes_phdrs
&& !map->includes_filehdr
&& map->p_paddr_valid)
/* There is some other padding before the first section.*/
map->p_vaddr_offset = ((lowest_section ? lowest_section->lma : 0)
- segment->p_paddr);
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