diff options
Diffstat (limited to 'src/elf.c')
| -rw-r--r-- | src/elf.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/src/elf.c b/src/elf.c new file mode 100644 index 0000000..da47502 --- /dev/null +++ b/src/elf.c @@ -0,0 +1,156 @@ +/* SPDX-License-Identifier: copyleft-next-0.3.1 */ +/* Copyright 2021 - 2022, Kim Kuparinen < kimi.h.kuparinen@gmail.com > */ + +/** + * @file elf.c + * Handle elf executables, set up requested memory mappings etc. + */ + +#include <kmi/elf.h> +#include <kmi/vmem.h> +#include <kmi/bits.h> +#include <kmi/string.h> +#include <kmi/assert.h> + +/** + * Convert ELF flags to page flags. + * + * @param elf_flags ELF flags to convert. + * @return Corresponding page flags. + */ +static uint8_t __elf_to_uvflags(uint8_t elf_flags) +{ + uint8_t uvflags = VM_V | VM_U; + if (elf_flags & PF_X) + uvflags |= VM_X; + + if (elf_flags & PF_W) + uvflags |= VM_W; + + if (elf_flags & PF_R) + uvflags |= VM_R; + + return uvflags; +} + +/** + * Map ELF executable. + * + * @param t Thread space to work in. + * @param bin Address of binary to map. + * @param ei_c ELF identity class. + * @param phstart Program header start. + * @param phnum Number of program header entries. + * @param phsize Size of page header entry. + */ +static void __map_exec(struct tcb *t, vm_t bin, uint8_t ei_c, vm_t phstart, + size_t phnum, size_t phsize) +{ + hard_assert(t && is_proc(t), RETURN_VOID); + + /** \todo take alignment into consideration? */ + /** \todo take overlapping memory regions into account, probably mostly + * by keeping track of previously allocated area and seeing if the + * segment fits into it */ + /** \todo check if p_memsz is larger than p_filesz, the segment should be + * filled with zeroes. */ + /** \todo in general, make this a lot more clean. */ + /* useful bit of info: all segments are sorted in ascending order of p_vaddr */ + vm_t runner = phstart; + vmflags_t default_flags = VM_V | VM_R | VM_W | VM_X | VM_U; + for (size_t i = 0; i < phnum; ++i, runner += phsize) { + if (program_header_prop(ei_c, runner, p_type) != PT_LOAD) + continue; + + vm_t va = program_header_prop(ei_c, runner, p_vaddr); + size_t vsz = program_header_prop(ei_c, runner, p_memsz); + + vm_t start = alloc_fixed_region(&t->sp_r, va, vsz, &vsz, + default_flags); + if (!start) + return; /* out of memory or something */ + + uint8_t elf_flags = program_header_prop(ei_c, runner, p_flags); + uint8_t uvflags = __elf_to_uvflags(elf_flags); + + map_allocd_region(t->proc.vmem, start, vsz, default_flags, 0); + memset((void *)start, 0, vsz); + + vm_t vo = bin + program_header_prop(ei_c, runner, p_offset); + vm_t vfz = program_header_prop(ei_c, runner, p_filesz); + memcpy((void *)va, (void *)vo, vfz); + + /* skip while testing + * \todo: also fix, this modifies only the first region. Create new + * function? + * + pm_t paddr = 0; + stat_vpage(t->b_r, va, &paddr, 0, 0); + mod_vpage(t->b_r, va, paddr, uvflags); + */ + } +} + +/** + * Map ELF dynamic object. + * + * @param t Thread space to work in. + * @param bin Address of binary to map. + * @param ei_c ELF identity class. + * @param phstart Program header start. + * @param phnum Number of program header entries. + * @param phsize Size of page header entry. + * @return Base of dynamic mapping. + */ +static vm_t __map_dyn(struct tcb *t, vm_t bin, uint8_t ei_c, vm_t phstart, + size_t phnum, size_t phsize) +{ + /** \todo this path should only be taken when no PT_INTERP is defined, as + * making sure ld is loaded should be done in userspace. Maybe a bit + * hacky, I know.*/ +} + +/** + * Map binary and optional interpreter. + * + * \todo Implement interpeter handling. + * + * @param t Thread space to work in. + * @param ei_c ELF identity class. (Of binary, should do one for interp?) + * @param elf ELF binary. + * @param interp ELF interpeter. + * @return Entry address. + */ +static vm_t __prepare_proc(struct tcb *t, uint8_t ei_c, vm_t elf, vm_t interp) +{ + short e_type = elf_header_prop(ei_c, elf, e_type); + if (e_type != ET_DYN && e_type != ET_EXEC) + return 0; + + vm_t phstart = ptradd(elf, elf_header_prop(ei_c, elf, e_phoff)); + size_t phnum = elf_header_prop(ei_c, elf, e_phnum); + size_t phsize = elf_header_prop(ei_c, elf, e_phentsize); + + vm_t entry = elf_header_prop(ei_c, elf, e_entry); + if (e_type == ET_EXEC) { + __map_exec(t, elf, ei_c, phstart, phnum, phsize); + return entry; + } else { + vm_t o = __map_dyn(t, elf, ei_c, phstart, phnum, phsize); + return o + entry; + } +} + +/* sets up all memory regions etc, returns the entry address */ +vm_t load_elf(struct tcb *t, vm_t elf, vm_t interp) +{ + struct elf_ident *i = (struct elf_ident *)elf; + if (i->ei_magic != cpu_to_be32(EI_MAGIC)) + return 0; + + if (i->ei_class != ELFCLASS32 && i->ei_class != ELFCLASS64) + return 0; + + /* more sanity checks? */ + return __prepare_proc(t, i->ei_class, elf, interp); +} |