From 696025802ec3273fde5cbf82c215a3d795435c1a Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 12 Jan 2015 15:24:20 +0100 Subject: gas: allow labeling of CFI instructions When runtime patching code (like e.g. done by the Linux kernel) there may be cases where the set of stack frame alterations differs between unpatched and patched code. Consequently the corresponding unwind data needs patching too. Locating the right places within an FDE, however, is rather cumbersome without a way to insert labels in the resulting section. Hence this patch introduces a new directive, .cfi_label. Note that with the way CFI data gets emitted currently (at the end of the assembly process) this can't support local FB- and dollar-labels. gas/ 2015-01-12 Jan Beulich * gas/dw2gencfi.c (cfi_add_label, dot_cfi_label): New. (cfi_pseudo_table): Add "cfi_label". (output_cfi_insn): Handle CFI_label. (select_cie_for_fde): Als terminate CIE when encountering CFI_label. * dw2gencfi.h (cfi_add_label): Declare. (struct cfi_insn_data): New member "sym_name". (CFI_label): New. * read.c (read_symbol_name): Drop "static". * read.h (read_symbol_name): Declare. gas/testsuite/ 2015-01-12 Jan Beulich gas/cfi/cfi-label.d, gas/cfi/cfi-label.s: New. gas/cfi/cfi.exp: Run new tests. --- gas/dw2gencfi.c | 41 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 40 insertions(+), 1 deletion(-) (limited to 'gas/dw2gencfi.c') diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c index 939c41a..6a80d0b 100644 --- a/gas/dw2gencfi.c +++ b/gas/dw2gencfi.c @@ -440,6 +440,19 @@ cfi_add_advance_loc (symbolS *label) frchain_now->frch_cfi_data->last_address = label; } +/* Add a CFI insn to label the current position in the CFI segment. */ + +void +cfi_add_label (const char *name) +{ + unsigned int len = strlen (name) + 1; + struct cfi_insn_data *insn = alloc_cfi_insn_data (); + + insn->insn = CFI_label; + obstack_grow (¬es, name, len); + insn->u.sym_name = (char *) obstack_finish (¬es); +} + /* Add a DW_CFA_offset record to the CFI data. */ void @@ -550,6 +563,7 @@ static void dot_cfi_endproc (int); static void dot_cfi_personality (int); static void dot_cfi_lsda (int); static void dot_cfi_val_encoded_addr (int); +static void dot_cfi_label (int); const pseudo_typeS cfi_pseudo_table[] = { @@ -575,6 +589,7 @@ const pseudo_typeS cfi_pseudo_table[] = { "cfi_personality", dot_cfi_personality, 0 }, { "cfi_lsda", dot_cfi_lsda, 0 }, { "cfi_val_encoded_addr", dot_cfi_val_encoded_addr, 0 }, + { "cfi_label", dot_cfi_label, 0 }, { NULL, NULL, 0 } }; @@ -1016,6 +1031,25 @@ dot_cfi_val_encoded_addr (int ignored ATTRIBUTE_UNUSED) demand_empty_rest_of_line (); } +static void +dot_cfi_label (int ignored ATTRIBUTE_UNUSED) +{ + char *name = read_symbol_name (); + + if (name == NULL) + return; + + /* If the last address was not at the current PC, advance to current. */ + if (symbol_get_frag (frchain_now->frch_cfi_data->last_address) != frag_now + || S_GET_VALUE (frchain_now->frch_cfi_data->last_address) + != frag_now_fix ()) + cfi_add_advance_loc (symbol_temp_new_now ()); + + cfi_add_label (name); + + demand_empty_rest_of_line (); +} + /* By default emit .eh_frame only, not .debug_frame. */ #define CFI_EMIT_eh_frame (1 << 0) #define CFI_EMIT_debug_frame (1 << 1) @@ -1386,6 +1420,10 @@ output_cfi_insn (struct cfi_insn_data *insn) } break; + case CFI_label: + colon (insn->u.sym_name); + break; + default: abort (); } @@ -1761,7 +1799,8 @@ select_cie_for_fde (struct fde_entry *fde, bfd_boolean eh_frame, if (i->insn == DW_CFA_advance_loc || i->insn == DW_CFA_remember_state || i->insn == CFI_escape - || i->insn == CFI_val_encoded_addr) + || i->insn == CFI_val_encoded_addr + || i->insn == CFI_label) break; cie->last = i; -- cgit v1.1