void DwarfBuf::dwarf_cfa_sfp(uint8_t reg, int offset, int scale) {
DwarfBuf b;
byte(DW_CFA_val_expression);
byte(reg);
b.dwarf_sfp_expr(offset, scale);
/* this assumes expression fits in 127 bytes, else we have
to LEB128 encode size */
byte(b.size());
dwarf_sfp_expr(offset, scale);
}
bool ElfWriter::addFrameInfo(DwarfChunk* d) {
Dwarf_Error error = 0;
DwarfBuf& b = d->m_buf;
b.clear();
/* Define common set of rules for unwinding frames in the VM stack*/
/* Frame pointer (CFA) for previous frame is in RBP + 16 */
b.dwarf_cfa_def_cfa(RBP, CFA_OFFSET);
/* Previous RIP is at CFA - 1 . DWARF_DATA_ALIGN (8) */
b.dwarf_cfa_offset_extended_sf(RIP, -1);
/* Previous RBP is at CFA - 2 . DWARF_DATA_ALIGN (8) */
b.dwarf_cfa_offset_extended_sf(RBP, -2);
/*
* RSP is unchanged in VM frames, except for some rare cases with
* calls to functions that we assume don't throw. (Technically
* debug information will be wrong if we stop under one of those
* cases.)
*
* Note: if rVmSp is ever changed to refer to rsp, this code needs
* to change.
*/
b.dwarf_cfa_same_value(RSP);
/* register above rules in a CIE (common information entry) */
Dwarf_Signed cie_index = dwarf_add_frame_cie(
m_dwarfProducer,
"",
DWARF_CODE_ALIGN,
DWARF_DATA_ALIGN,
RIP,
(void *)b.getBuf(),
b.size(),
&error
);
if (cie_index == DW_DLV_NOCOUNT) {
logError("Unable to add CIE frame");
return false;
}
/* for each tracelet, register tracelet address ranges in
* an FDE (Frame Description entry) */
FuncPtrDB::iterator it;
for (it = d->m_functions.begin(); it != d->m_functions.end(); it++) {
Dwarf_P_Fde fde = dwarf_new_fde(m_dwarfProducer, &error);
if (reinterpret_cast<Dwarf_Addr>(fde) == DW_DLV_BADADDR) {
logError("Unable to create FDE");
return false;
}
DwarfBuf buf;
int err = dwarf_insert_fde_inst_bytes(
m_dwarfProducer, fde, buf.size(), buf.getBuf(), &error);
if (err == DW_DLV_ERROR) {
logError("Unable to add instructions to fde");
return false;
}
Dwarf_Unsigned fde_index = dwarf_add_frame_fde(
m_dwarfProducer, fde, 0, cie_index,
(Dwarf_Unsigned)((*it)->range.begin()),
(*it)->range.size(),
0, &error);
if (fde_index == DW_DLV_BADADDR) {
logError("Unable to add FDE");
return false;
}
}
return true;
}
