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Extend ELF coredump to support more than 65535 segments

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The ELF e_phnum field is only 16 bits wide. To support more than 65535 segments
(program headers), Sun's "Linker and Libraries Guide" table 7-7 (or 12-7,
depending on document version) prescribes a special first section header where
sh_info represents the real number of program headers.

Test code to follow, when it is ready.

Reference:	http://docs.oracle.com/cd/E18752_01/pdf/817-1984.pdf

Reviewed by:	emaste, markj
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D7255
This commit is contained in:
Conrad Meyer 2016-07-20 16:59:36 +00:00
parent 9f3391243b
commit c17b0bd2a6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=303099
1 changed files with 34 additions and 3 deletions
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37
sys/kern/imgact_elf.c
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@ -1323,6 +1323,8 @@ __elfN(coredump)(struct thread *td, struct vnode *vp, off_t limit, int flags)
* Collect info about the core file header area.
*/
hdrsize = sizeof(Elf_Ehdr) + sizeof(Elf_Phdr) * (1 + seginfo.count);
if (seginfo.count + 1 >= PN_XNUM)
hdrsize += sizeof(Elf_Shdr);
__elfN(prepare_notes)(td, &notelst, &notesz);
coresize = round_page(hdrsize + notesz) + seginfo.size;
@ -1618,10 +1620,10 @@ __elfN(puthdr)(struct thread *td, void *hdr, size_t hdrsize, int numsegs,
{
Elf_Ehdr *ehdr;
Elf_Phdr *phdr;
Elf_Shdr *shdr;
struct phdr_closure phc;
ehdr = (Elf_Ehdr *)hdr;
phdr = (Elf_Phdr *)((char *)hdr + sizeof(Elf_Ehdr));
ehdr->e_ident[EI_MAG0] = ELFMAG0;
ehdr->e_ident[EI_MAG1] = ELFMAG1;
@ -1645,14 +1647,43 @@ __elfN(puthdr)(struct thread *td, void *hdr, size_t hdrsize, int numsegs,
ehdr->e_flags = 0;
ehdr->e_ehsize = sizeof(Elf_Ehdr);
ehdr->e_phentsize = sizeof(Elf_Phdr);
ehdr->e_phnum = numsegs + 1;
ehdr->e_shentsize = sizeof(Elf_Shdr);
ehdr->e_shnum = 0;
ehdr->e_shstrndx = SHN_UNDEF;
if (numsegs + 1 < PN_XNUM) {
ehdr->e_phnum = numsegs + 1;
ehdr->e_shnum = 0;
} else {
ehdr->e_phnum = PN_XNUM;
ehdr->e_shnum = 1;
ehdr->e_shoff = ehdr->e_phoff +
(numsegs + 1) * ehdr->e_phentsize;
KASSERT(ehdr->e_shoff == hdrsize - sizeof(Elf_Shdr),
("e_shoff: %zu, hdrsize - shdr: %zu",
ehdr->e_shoff, hdrsize - sizeof(Elf_Shdr)));
shdr = (Elf_Shdr *)((char *)hdr + ehdr->e_shoff);
memset(shdr, 0, sizeof(*shdr));
/*
* A special first section is used to hold large segment and
* section counts. This was proposed by Sun Microsystems in
* Solaris and has been adopted by Linux; the standard ELF
* tools are already familiar with the technique.
*
* See table 7-7 of the Solaris "Linker and Libraries Guide"
* (or 12-7 depending on the version of the document) for more
* details.
*/
shdr->sh_type = SHT_NULL;
shdr->sh_size = ehdr->e_shnum;
shdr->sh_link = ehdr->e_shstrndx;
shdr->sh_info = numsegs + 1;
}
/*
* Fill in the program header entries.
*/
phdr = (Elf_Phdr *)((char *)hdr + ehdr->e_phoff);
/* The note segement. */
phdr->p_type = PT_NOTE;