/**
* @brief Checks access permissions to a memory area.
*
* @param addr Address to be checked.
* @param size Size of memory area.
* @param mask Access permissions mask.
*
* @returns Non-zero if access is authorized, and zero otherwise.
*/
PUBLIC int chkmem(const void *addr, size_t size, mode_t mask)
{
int ret; /* Return value. */
struct region *reg; /* Working memory region. */
struct pregion *preg; /* Working process region. */
/* Get associated process memory region. */
if ((preg = findreg(curr_proc, ADDR(addr))) == NULL)
return (-1);
lockreg(reg = preg->reg);
/* Not allowed. */
if (!(accessreg(curr_proc, reg) & mask))
{
unlockreg(reg);
return (-1);
}
ret = withinreg(preg, ADDR(addr));
ret &= withinreg(preg, ADDR(addr) + size);
unlockreg(reg);
return (ret);
}
/*
* Loads an ELF 32 executable.
*/
PRIVATE addr_t load_elf32(struct inode *inode)
{
int i; /* Loop index. */
addr_t addr; /* Region address. */
addr_t entry; /* Program entry point. */
struct elf32_fhdr *elf; /* ELF file header. */
struct elf32_phdr *seg; /* ELF Program header. */
block_t blk; /* Working block number. */
buffer_t header; /* File headers block buffer. */
struct region *reg; /* Working memory region. */
struct pregion *preg; /* Working process memory region. */
blk = block_map(inode, 0, 0);
/* Empty file. */
if (blk == BLOCK_NULL)
{
curr_proc->errno = -ENOEXEC;
return (0);
}
/* Read ELF file header. */
header = bread(inode->dev, blk);
elf = buffer_data(header);
/* Bad ELF file. */
if (!is_elf(elf))
{
brelse(header);
curr_proc->errno = -ENOEXEC;
return (0);
}
/* Bad ELF file. */
if (elf->e_phoff + elf->e_phnum*elf->e_phentsize > BLOCK_SIZE)
{
brelse(header);
curr_proc->errno = -ENOEXEC;
return (0);
}
seg = (struct elf32_phdr *)((char *)buffer_data(header) + elf->e_phoff);
/* Load segments. */
for (i = 0; i < elf->e_phnum; i++)
{
/* Not loadable. */
if (seg[i].p_type != PT_LOAD)
continue;
/* Broken executable. */
if (seg[i].p_filesz > seg[i].p_memsz)
{
kprintf("broken executable");
brelse(header);
curr_proc->errno = -ENOEXEC;
return (0);
}
addr = ALIGN(seg[i].p_vaddr, seg[i].p_align);
/* Text section. */
if (!(seg[i].p_flags ^ (PF_R | PF_X)))
{
preg = TEXT(curr_proc);
reg = allocreg(S_IRUSR | S_IXUSR, seg[i].p_memsz, 0);
}
/* Data section. */
else
{
preg = DATA(curr_proc);
reg = allocreg(S_IRUSR | S_IWUSR, seg[i].p_memsz, 0);
}
/* Failed to allocate region. */
if (reg == NULL)
{
brelse(header);
curr_proc->errno = -ENOMEM;
return (0);
}
/* Attach memory region. */
if (attachreg(curr_proc, preg, addr, reg))
{
freereg(reg);
brelse(header);
curr_proc->errno = -ENOMEM;
return (0);
}
loadreg(inode, reg, seg[i].p_offset, seg[i].p_filesz);
unlockreg(reg);
}
entry = elf->e_entry;
brelse(header);
return (entry);
}
/*
* Executes a program.
*/
PUBLIC int sys_execve(const char *filename, const char **argv, const char **envp)
{
int i; /* Loop index. */
struct inode *inode; /* File inode. */
struct region *reg; /* Process region. */
addr_t entry; /* Program entry point. */
addr_t sp; /* User stack pointer. */
char *name; /* File name. */
char stack[ARG_MAX]; /* Stack size. */
/* Get file name. */
if ((name = getname(filename)) == NULL)
return (curr_proc->errno);
/* Build arguments before freeing user memory. */
kmemset(stack, 0, ARG_MAX);
if (!(sp = buildargs(stack, ARG_MAX, argv, envp)))
{
putname(name);
return (curr_proc->errno);
}
/* Get file's inode. */
if ((inode = inode_name(name)) == NULL)
{
putname(name);
return (curr_proc->errno);
}
/* Not a regular file. */
if (!S_ISREG(inode->mode))
{
putname(name);
inode_put(inode);
return (-EACCES);
}
/* Not allowed. */
if (!permission(inode->mode, inode->uid, inode->gid, curr_proc, MAY_EXEC, 0))
{
putname(name);
inode_put(inode);
return (-EACCES);
}
/* Close file descriptors. */
for (i = 0; i < OPEN_MAX; i++)
{
if (curr_proc->close & (1 << i))
do_close(i);
}
/* Detach process memory regions. */
for (i = 0; i < NR_PREGIONS; i++)
detachreg(curr_proc, &curr_proc->pregs[i]);
/* Reset signal handlers. */
curr_proc->restorer = NULL;
for (i = 0; i < NR_SIGNALS; i++)
{
if (curr_proc->handlers[i] != SIG_DFL)
{
if (curr_proc->handlers[i] != SIG_IGN)
curr_proc->handlers[i] = SIG_DFL;
}
}
/* Load executable. */
if (!(entry = load_elf32(inode)))
goto die0;
/* Attach stack region. */
if ((reg = allocreg(S_IRUSR | S_IWUSR, PAGE_SIZE, REGION_DOWNWARDS)) == NULL)
goto die0;
if (attachreg(curr_proc, STACK(curr_proc), USTACK_ADDR - 1, reg))
goto die1;
unlockreg(reg);
/* Attach heap region. */
if ((reg = allocreg(S_IRUSR | S_IWUSR, PAGE_SIZE, REGION_UPWARDS)) == NULL)
goto die0;
if (attachreg(curr_proc, HEAP(curr_proc), UHEAP_ADDR, reg))
goto die1;
unlockreg(reg);
inode_put(inode);
putname(name);
kmemcpy((void *)(USTACK_ADDR - ARG_MAX), stack, ARG_MAX);
user_mode(entry, sp);
/* Will not return. */
return (0);
die1:
unlockreg(reg);
freereg(reg);
die0:
inode_put(inode);
putname(name);
die(((SIGSEGV & 0xff) << 16) | (1 << 9));
return (-1);
}
