1// See LICENSE for license details.
2
3#include "pk.h"
4#include "mtrap.h"
5#include "boot.h"
6#include "bits.h"
7#include "elf.h"
8#include <sys/stat.h>
9#include <fcntl.h>
10#include <string.h>
11#include "mmap.h"
12
13/**
14 * The protection flags are in the p_flags section of the program header.
15 * But rather annoyingly, they are the reverse of what mmap expects.
16 */
17static inline int get_prot(uint32_t p_flags)
18{
19  int prot_x = (p_flags & PF_X) ? PROT_EXEC  : PROT_NONE;
20  int prot_w = (p_flags & PF_W) ? PROT_WRITE : PROT_NONE;
21  int prot_r = (p_flags & PF_R) ? PROT_READ  : PROT_NONE;
22
23  return (prot_x | prot_w | prot_r);
24}
25
26void load_elf(const char* fn, elf_info* info)
27{
28  file_t* file = file_open(fn, O_RDONLY, 0);
29  if (IS_ERR_VALUE(file))
30    goto fail;
31
32  Elf_Ehdr eh;
33  ssize_t ehdr_size = file_pread(file, &eh, sizeof(eh), 0);
34  if (ehdr_size < (ssize_t)sizeof(eh) ||
35      !(eh.e_ident[0] == '\177' && eh.e_ident[1] == 'E' &&
36        eh.e_ident[2] == 'L'    && eh.e_ident[3] == 'F'))
37    goto fail;
38
39#if __riscv_xlen == 64
40  assert(IS_ELF64(eh));
41#else
42  assert(IS_ELF32(eh));
43#endif
44
45#ifndef __riscv_compressed
46  assert(!(eh.e_flags & EF_RISCV_RVC));
47#endif
48
49  size_t phdr_size = eh.e_phnum * sizeof(Elf_Phdr);
50  if (phdr_size > info->phdr_size)
51    goto fail;
52  ssize_t ret = file_pread(file, (void*)info->phdr, phdr_size, eh.e_phoff);
53  if (ret < (ssize_t)phdr_size)
54    goto fail;
55  info->phnum = eh.e_phnum;
56  info->phent = sizeof(Elf_Phdr);
57  Elf_Phdr* ph = (typeof(ph))info->phdr;
58
59  // compute highest VA in ELF
60  uintptr_t max_vaddr = 0;
61  for (int i = 0; i < eh.e_phnum; i++)
62    if (ph[i].p_type == PT_LOAD && ph[i].p_memsz)
63      max_vaddr = MAX(max_vaddr, ph[i].p_vaddr + ph[i].p_memsz);
64  max_vaddr = ROUNDUP(max_vaddr, RISCV_PGSIZE);
65
66  // don't load dynamic linker at 0, else we can't catch NULL pointer derefs
67  uintptr_t bias = 0;
68  if (eh.e_type == ET_DYN)
69    bias = RISCV_PGSIZE;
70
71  info->entry = eh.e_entry + bias;
72  int flags = MAP_FIXED | MAP_PRIVATE;
73  for (int i = eh.e_phnum - 1; i >= 0; i--) {
74    if(ph[i].p_type == PT_LOAD && ph[i].p_memsz) {
75      uintptr_t prepad = ph[i].p_vaddr % RISCV_PGSIZE;
76      uintptr_t vaddr = ph[i].p_vaddr + bias;
77      if (vaddr + ph[i].p_memsz > info->brk_min)
78        info->brk_min = vaddr + ph[i].p_memsz;
79      int flags2 = flags | (prepad ? MAP_POPULATE : 0);
80      int prot = get_prot(ph[i].p_flags);
81      if (__do_mmap(vaddr - prepad, ph[i].p_filesz + prepad, prot | PROT_WRITE, flags2, file, ph[i].p_offset - prepad) != vaddr - prepad)
82        goto fail;
83      memset((void*)vaddr - prepad, 0, prepad);
84      if (!(prot & PROT_WRITE))
85        if (do_mprotect(vaddr - prepad, ph[i].p_filesz + prepad, prot))
86          goto fail;
87      size_t mapped = ROUNDUP(ph[i].p_filesz + prepad, RISCV_PGSIZE) - prepad;
88      if (ph[i].p_memsz > mapped)
89        if (__do_mmap(vaddr + mapped, ph[i].p_memsz - mapped, prot, flags|MAP_ANONYMOUS, 0, 0) != vaddr + mapped)
90          goto fail;
91    }
92  }
93
94  file_decref(file);
95  return;
96
97fail:
98  panic("couldn't open ELF program: %s!", fn);
99}
100