From ac028085563082ba9262a5fbd050c3422c7fcff0 Mon Sep 17 00:00:00 2001 From: Konstantin Baladurin Date: Tue, 17 Oct 2017 21:27:53 +0300 Subject: [PATCH] dwarf/Gparser: fix crash during unwinding (#44) We should update locations of the registers after all of them will be restored. Otherwise some locations will be incorrect. For example if function stores ebp, edi, esi and ebx registers on stack in its prologue, compiler can generate following unwind info: DW_CFA_expression: r5 (ebp) (DW_OP_breg5 (ebp): 0) DW_CFA_expression: r7 (edi) (DW_OP_breg5 (ebp): -4) DW_CFA_expression: r6 (esi) (DW_OP_breg5 (ebp): -8) DW_CFA_expression: r3 (ebx) (DW_OP_breg5 (ebp): -12) In this case locations of the ebx and ebp will be calculated using current ebp but locations of the esi and edi will be calculated using previous (restored) one. Due to it their locations will be incorrect and it could lead to crash if we will try to get esi or edi value. This patch fixes this problem. --- src/dwarf/Gparser.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c index 3a47255c..455124b5 100644 --- a/src/dwarf/Gparser.c +++ b/src/dwarf/Gparser.c @@ -776,40 +776,45 @@ apply_reg_state (struct dwarf_cursor *c, struct dwarf_reg_state *rs) cfa = DWARF_GET_LOC (cfa_loc); } + dwarf_loc_t new_loc[DWARF_NUM_PRESERVED_REGS]; + memcpy(new_loc, c->loc, sizeof(new_loc)); + for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i) { switch ((dwarf_where_t) rs->reg[i].where) { case DWARF_WHERE_UNDEF: - c->loc[i] = DWARF_NULL_LOC; + new_loc[i] = DWARF_NULL_LOC; break; case DWARF_WHERE_SAME: break; case DWARF_WHERE_CFAREL: - c->loc[i] = DWARF_MEM_LOC (c, cfa + rs->reg[i].val); + new_loc[i] = DWARF_MEM_LOC (c, cfa + rs->reg[i].val); break; case DWARF_WHERE_REG: - c->loc[i] = DWARF_REG_LOC (c, dwarf_to_unw_regnum (rs->reg[i].val)); + new_loc[i] = DWARF_REG_LOC (c, dwarf_to_unw_regnum (rs->reg[i].val)); break; case DWARF_WHERE_EXPR: addr = rs->reg[i].val; - if ((ret = eval_location_expr (c, as, a, addr, c->loc + i, arg)) < 0) + if ((ret = eval_location_expr (c, as, a, addr, new_loc + i, arg)) < 0) return ret; break; case DWARF_WHERE_VAL_EXPR: addr = rs->reg[i].val; - if ((ret = eval_location_expr (c, as, a, addr, c->loc + i, arg)) < 0) + if ((ret = eval_location_expr (c, as, a, addr, new_loc + i, arg)) < 0) return ret; - c->loc[i] = DWARF_VAL_LOC (c, DWARF_GET_LOC (c->loc[i])); + new_loc[i] = DWARF_VAL_LOC (c, DWARF_GET_LOC (new_loc[i])); break; } } + memcpy(c->loc, new_loc, sizeof(new_loc)); + c->cfa = cfa; /* DWARF spec says undefined return address location means end of stack. */ if (DWARF_IS_NULL_LOC (c->loc[c->ret_addr_column]))