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tinycc/x86_64-link.c
herman ten brugge 853a498f2c Fix boundschecking for signal/sigaction/fork 
The BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF is not working for
signal/sigaction/fork. The reason is that the code stops bound checking
for the whole application. This result in wrong handling of
__bound_local_new/__bound_local_delete and malloc/calloc/realloc/free.
Consider the following code:

void tst(int n) {
  int i, arr[n];
  for (i = 0; i < n; i++) arr[i] = 0;
}

void *some_thread(void *dummy) {
  while (running) { tst(10); tst(20); }
}

void signal_handler(int sig) { ... }

When the signal handler is called the some_thread code can be interrupted when
is just registered the arr[10] data. When the signal handler is leaved the
arr[10] is still registered and did not see the call to deregister arr[10] and
then register arr[20]. The code resumes when tst(20) is running. This results
in a bound checking error when i >= 10.

To solve the above problem I changed the bound checking code to use
tls (thread local storage) for the no_checking variable.
This also makes it now possible to redirect signal/sigaction/fork code
through the bound checking library and disable checking when a signal is
running and to correct the bounds_sem for the fork child process.
The BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF is not needed any more for
signal/sigaction/fork. In fact I could remove them from all my applications.

The use of the tls function code slows down the code by about 10%.
So if the slowdown due to bound checking was 5. It is now 5.5 times slower.

For x86_64/i386 I also allowed to use __thread variable in bcheck.c when
compiled with gcc with:
make x86_64-libtcc1-usegcc=yes
make i386-libtcc1-usegcc=yes
This makes code run faster due to use of gcc and __thread variable.
With the __thread variable there is no 10% slowdown.
For other targets this does not work because stabs is not supported.

Changes:

lib/bcheck.c:
- Add TRY_SEM
- Add HAVE_SIGNAL/HAVE_SIGACTION/HAVE_FORK/HAVE_TLS_FUNC/HAVE_TLS_VAR
  - HAVE_SIGNAL: redirect signal() call if set.
  - HAVE_SIGACTION: redirect sigaction() call if set.
  - HAVE_FORK: redirect fork() call if set.
  - HAVE_TLS_FUNC: If target has tls function calls.
  - HAVE_TLS_VAR: If target has __thread tls support.
- Replace all no_checking refecrences to NO_CHECKING_SET/NO_CHECKING_GET macros

tcc-doc.texi:
- Remove examples for signal/sigaction/fork code.
- Add some explanation for signal/sigaction/fork code.
- Add documentaion for __bounds_checking().

tccelf.c:
- Add support for SHF_TLS

tests/tests2/114_bound_signal.c:
- Remove BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF
- Add code to trigger failure when tls is not working.

x86_64-link.c:
- Add support for R_X86_64_TLSGD/R_X86_64_TLSLD/R_X86_64_DTPOFF32/R_X86_64_TPOFF32

i386-link.c:
- Add support for R_386_TLS_GD/R_386_TLS_LDM/R_386_TLS_LDO_32/R_386_TLS_LE
2020-09-08 14:31:58 +02:00

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#ifdef TARGET_DEFS_ONLY
#define EM_TCC_TARGET EM_X86_64
/* relocation type for 32 bit data relocation */
#define R_DATA_32 R_X86_64_32S
#define R_DATA_PTR R_X86_64_64
#define R_JMP_SLOT R_X86_64_JUMP_SLOT
#define R_GLOB_DAT R_X86_64_GLOB_DAT
#define R_COPY R_X86_64_COPY
#define R_RELATIVE R_X86_64_RELATIVE
#define R_NUM R_X86_64_NUM
#define ELF_START_ADDR 0x400000
#define ELF_PAGE_SIZE 0x200000
#define PCRELATIVE_DLLPLT 1
#define RELOCATE_DLLPLT 1
#else /* !TARGET_DEFS_ONLY */
#include "tcc.h"
#if !defined(ELF_OBJ_ONLY) || defined(TCC_TARGET_MACHO)
/* Returns 1 for a code relocation, 0 for a data relocation. For unknown
relocations, returns -1. */
int code_reloc (int reloc_type)
{
switch (reloc_type) {
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPC64:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_GOTTPOFF:
case R_X86_64_GOT32:
case R_X86_64_GOT64:
case R_X86_64_GLOB_DAT:
case R_X86_64_COPY:
case R_X86_64_RELATIVE:
case R_X86_64_GOTOFF64:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
return 0;
case R_X86_64_PC32:
case R_X86_64_PC64:
case R_X86_64_PLT32:
case R_X86_64_PLTOFF64:
case R_X86_64_JUMP_SLOT:
return 1;
}
return -1;
}
/* Returns an enumerator to describe whether and when the relocation needs a
GOT and/or PLT entry to be created. See tcc.h for a description of the
different values. */
int gotplt_entry_type (int reloc_type)
{
switch (reloc_type) {
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
case R_X86_64_COPY:
case R_X86_64_RELATIVE:
return NO_GOTPLT_ENTRY;
/* The following relocs wouldn't normally need GOT or PLT
slots, but we need them for simplicity in the link
editor part. See our caller for comments. */
case R_X86_64_32:
case R_X86_64_32S:
case R_X86_64_64:
case R_X86_64_PC32:
case R_X86_64_PC64:
return AUTO_GOTPLT_ENTRY;
case R_X86_64_GOTTPOFF:
return BUILD_GOT_ONLY;
case R_X86_64_GOT32:
case R_X86_64_GOT64:
case R_X86_64_GOTPC32:
case R_X86_64_GOTPC64:
case R_X86_64_GOTOFF64:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_PLT32:
case R_X86_64_PLTOFF64:
return ALWAYS_GOTPLT_ENTRY;
}
return -1;
}
#if !defined(TCC_TARGET_MACHO) || defined TCC_IS_NATIVE
ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
{
Section *plt = s1->plt;
uint8_t *p;
int modrm;
unsigned plt_offset, relofs;
modrm = 0x25;
/* empty PLT: create PLT0 entry that pushes the library identifier
(GOT + PTR_SIZE) and jumps to ld.so resolution routine
(GOT + 2 * PTR_SIZE) */
if (plt->data_offset == 0) {
p = section_ptr_add(plt, 16);
p[0] = 0xff; /* pushl got + PTR_SIZE */
p[1] = modrm + 0x10;
write32le(p + 2, PTR_SIZE);
p[6] = 0xff; /* jmp *(got + PTR_SIZE * 2) */
p[7] = modrm;
write32le(p + 8, PTR_SIZE * 2);
}
plt_offset = plt->data_offset;
/* The PLT slot refers to the relocation entry it needs via offset.
The reloc entry is created below, so its offset is the current
data_offset */
relofs = s1->got->reloc ? s1->got->reloc->data_offset : 0;
/* Jump to GOT entry where ld.so initially put the address of ip + 4 */
p = section_ptr_add(plt, 16);
p[0] = 0xff; /* jmp *(got + x) */
p[1] = modrm;
write32le(p + 2, got_offset);
p[6] = 0x68; /* push $xxx */
/* On x86-64, the relocation is referred to by _index_ */
write32le(p + 7, relofs / sizeof (ElfW_Rel));
p[11] = 0xe9; /* jmp plt_start */
write32le(p + 12, -(plt->data_offset));
return plt_offset;
}
/* relocate the PLT: compute addresses and offsets in the PLT now that final
address for PLT and GOT are known (see fill_program_header) */
ST_FUNC void relocate_plt(TCCState *s1)
{
uint8_t *p, *p_end;
if (!s1->plt)
return;
p = s1->plt->data;
p_end = p + s1->plt->data_offset;
if (p < p_end) {
int x = s1->got->sh_addr - s1->plt->sh_addr - 6;
add32le(p + 2, x);
add32le(p + 8, x - 6);
p += 16;
while (p < p_end) {
add32le(p + 2, x + (s1->plt->data - p));
p += 16;
}
}
}
#endif
#endif
void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
{
int sym_index, esym_index;
sym_index = ELFW(R_SYM)(rel->r_info);
switch (type) {
case R_X86_64_64:
if (s1->output_type == TCC_OUTPUT_DLL) {
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
qrel->r_offset = rel->r_offset;
if (esym_index) {
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_64);
qrel->r_addend = rel->r_addend;
qrel++;
break;
} else {
qrel->r_info = ELFW(R_INFO)(0, R_X86_64_RELATIVE);
qrel->r_addend = read64le(ptr) + val;
qrel++;
}
}
add64le(ptr, val);
break;
case R_X86_64_32:
case R_X86_64_32S:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* XXX: this logic may depend on TCC's codegen
now TCC uses R_X86_64_32 even for a 64bit pointer */
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(0, R_X86_64_RELATIVE);
/* Use sign extension! */
qrel->r_addend = (int)read32le(ptr) + val;
qrel++;
}
add32le(ptr, val);
break;
case R_X86_64_PC32:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* DLL relocation */
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
if (esym_index) {
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_PC32);
/* Use sign extension! */
qrel->r_addend = (int)read32le(ptr) + rel->r_addend;
qrel++;
break;
}
}
goto plt32pc32;
case R_X86_64_PLT32:
/* fallthrough: val already holds the PLT slot address */
plt32pc32:
{
long long diff;
diff = (long long)val - addr;
if (diff < -2147483648LL || diff > 2147483647LL) {
tcc_error("internal error: relocation failed");
}
add32le(ptr, diff);
}
break;
case R_X86_64_PLTOFF64:
add64le(ptr, val - s1->got->sh_addr + rel->r_addend);
break;
case R_X86_64_PC64:
if (s1->output_type == TCC_OUTPUT_DLL) {
/* DLL relocation */
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
if (esym_index) {
qrel->r_offset = rel->r_offset;
qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_PC64);
qrel->r_addend = read64le(ptr) + rel->r_addend;
qrel++;
break;
}
}
add64le(ptr, val - addr);
break;
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
/* They don't need addend */
write64le(ptr, val - rel->r_addend);
break;
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_REX_GOTPCRELX:
add32le(ptr, s1->got->sh_addr - addr +
get_sym_attr(s1, sym_index, 0)->got_offset - 4);
break;
case R_X86_64_GOTPC32:
add32le(ptr, s1->got->sh_addr - addr + rel->r_addend);
break;
case R_X86_64_GOTPC64:
add64le(ptr, s1->got->sh_addr - addr + rel->r_addend);
break;
case R_X86_64_GOTTPOFF:
add32le(ptr, val - s1->got->sh_addr);
break;
case R_X86_64_GOT32:
/* we load the got offset */
add32le(ptr, get_sym_attr(s1, sym_index, 0)->got_offset);
break;
case R_X86_64_GOT64:
/* we load the got offset */
add64le(ptr, get_sym_attr(s1, sym_index, 0)->got_offset);
break;
case R_X86_64_GOTOFF64:
add64le(ptr, val - s1->got->sh_addr);
break;
case R_X86_64_TLSGD:
{
static const unsigned char expect[] = {
/* .byte 0x66; lea 0(%rip),%rdi */
0x66, 0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* .word 0x6666; rex64; call __tls_get_addr@PLT */
0x66, 0x66, 0x48, 0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* mov %fs:0,%rax */
0x64, 0x48, 0x8b, 0x04, 0x25, 0x00, 0x00, 0x00, 0x00,
/* lea -4(%rax),%rax */
0x48, 0x8d, 0x80, 0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-4, expect, sizeof(expect)) == 0) {
ElfW(Sym) *sym;
Section *sec;
int32_t x;
memcpy(ptr-4, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = sym->st_value - sec->sh_addr - sec->data_offset;
add32le(ptr + 8, x);
}
else
tcc_error("unexpected R_X86_64_TLSGD pattern");
}
break;
case R_X86_64_TLSLD:
{
static const unsigned char expect[] = {
/* lea 0(%rip),%rdi */
0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* call __tls_get_addr@PLT */
0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* data16 data16 data16 mov %fs:0,%rax */
0x66, 0x66, 0x66, 0x64, 0x48, 0x8b, 0x04, 0x25,
0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-3, expect, sizeof(expect)) == 0) {
memcpy(ptr-3, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
}
else
tcc_error("unexpected R_X86_64_TLSLD pattern");
}
break;
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
{
ElfW(Sym) *sym;
Section *sec;
int32_t x;
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = val - sec->sh_addr - sec->data_offset;
add32le(ptr, x);
}
break;
case R_X86_64_NONE:
break;
case R_X86_64_RELATIVE:
#ifdef TCC_TARGET_PE
add32le(ptr, val - s1->pe_imagebase);
#endif
/* do nothing */
break;
}
}
#endif /* !TARGET_DEFS_ONLY */
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