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// See LICENSE for license details.
#include "pk.h"
#include "mtrap.h"
#include "boot.h"
#include "bits.h"
#include "elf.h"
#include "usermem.h"
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include "mmap.h"
/**
* The protection flags are in the p_flags section of the program header.
* But rather annoyingly, they are the reverse of what mmap expects.
*/
static inline int get_prot(uint32_t p_flags)
{
int prot_x = (p_flags & PF_X) ? PROT_EXEC : PROT_NONE;
int prot_w = (p_flags & PF_W) ? PROT_WRITE : PROT_NONE;
int prot_r = (p_flags & PF_R) ? PROT_READ : PROT_NONE;
return (prot_x | prot_w | prot_r);
}
void load_elf(const char* fn, elf_info* info)
{
file_t* file = file_open(fn, O_RDONLY, 0);
if (IS_ERR_VALUE(file))
goto fail;
Elf_Ehdr eh;
ssize_t ehdr_size = file_pread(file, &eh, sizeof(eh), 0);
if (ehdr_size < (ssize_t)sizeof(eh) ||
!(eh.e_ident[0] == '\177' && eh.e_ident[1] == 'E' &&
eh.e_ident[2] == 'L' && eh.e_ident[3] == 'F'))
goto fail;
#if __riscv_xlen == 64
assert(IS_ELF64(eh));
#else
assert(IS_ELF32(eh));
#endif
#ifndef __riscv_compressed
assert(!(eh.e_flags & EF_RISCV_RVC));
#endif
size_t phdr_size = eh.e_phnum * sizeof(Elf_Phdr);
if (phdr_size > info->phdr_size)
goto fail;
ssize_t ret = file_pread(file, (void*)info->phdr, phdr_size, eh.e_phoff);
if (ret < (ssize_t)phdr_size)
goto fail;
info->phnum = eh.e_phnum;
info->phent = sizeof(Elf_Phdr);
Elf_Phdr* ph = (typeof(ph))info->phdr;
// compute highest VA in ELF
uintptr_t max_vaddr = 0;
for (int i = 0; i < eh.e_phnum; i++)
if (ph[i].p_type == PT_LOAD && ph[i].p_memsz)
max_vaddr = MAX(max_vaddr, ph[i].p_vaddr + ph[i].p_memsz);
max_vaddr = ROUNDUP(max_vaddr, RISCV_PGSIZE);
// don't load dynamic linker at 0, else we can't catch NULL pointer derefs
uintptr_t bias = 0;
if (eh.e_type == ET_DYN)
bias = RISCV_PGSIZE;
info->entry = eh.e_entry + bias;
int flags = MAP_FIXED | MAP_PRIVATE;
for (int i = eh.e_phnum - 1; i >= 0; i--) {
if(ph[i].p_type == PT_INTERP) {
panic("not a statically linked ELF program");
}
if(ph[i].p_type == PT_LOAD && ph[i].p_memsz) {
if (ph[i].p_filesz > ph[i].p_memsz)
goto fail;
uintptr_t prepad = ph[i].p_vaddr % RISCV_PGSIZE;
uintptr_t vaddr = ph[i].p_vaddr + bias;
if (vaddr + ph[i].p_memsz > info->brk_min)
info->brk_min = vaddr + ph[i].p_memsz;
int flags2 = flags | (prepad ? MAP_POPULATE : 0);
int prot = get_prot(ph[i].p_flags);
if (__do_mmap(vaddr - prepad, ph[i].p_filesz + prepad, prot | PROT_WRITE, flags2, file, ph[i].p_offset - prepad) != vaddr - prepad)
goto fail;
memset_user((void*)vaddr - prepad, 0, prepad);
if (!(prot & PROT_WRITE))
if (do_mprotect(vaddr - prepad, ph[i].p_filesz + prepad, prot))
goto fail;
size_t mapped = ROUNDUP(ph[i].p_filesz + prepad, RISCV_PGSIZE) - prepad;
if (ph[i].p_memsz > mapped)
if (__do_mmap(vaddr + mapped, ph[i].p_memsz - mapped, prot, flags|MAP_ANONYMOUS, 0, 0) != vaddr + mapped)
goto fail;
}
}
file_decref(file);
info->brk = ROUNDUP(info->brk_min, RISCV_PGSIZE);
return;
fail:
panic("couldn't open ELF program: %s!", fn);
}
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