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dwarf2: Align relocation within .debug_line section

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All relocations specify a byte address.  As dwarf debug information is
organized in octets, some relocations may not be aligned.  While it
might be possible to define special relocations that operate at an
octet offset from their address, it's easier to ensure the relocations
are aligned by padding with "nop" statements.

In most dwarf sections this requirement is already fulfilled, only
relocations for symbol address within the .debug_line section can be
misaligned.

	* dwarf2dbg.c (out_set_addr): Align relocation within .debug_line.
This commit is contained in:
Christian Eggers 2019-03-10 19:21:58 +01:00 committed by Alan Modra
parent 145c4477d2
commit 204f543cae
2 changed files with 19 additions and 3 deletions
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4
gas/ChangeLog
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@ -1,3 +1,7 @@
2019-03-13 Christian Eggers <ceggers@gmx.de>
* dwarf2dbg.c (out_set_addr): Align relocation within .debug_line.
2019-03-13 Christian Eggers <ceggers@gmx.de>
* dwarf2dbg.c (out_debug_line): Pad size of .debug_line section.

18
gas/dwarf2dbg.c
View File

@ -1108,16 +1108,28 @@ get_frag_fix (fragS *frag, segT seg)
/* Set an absolute address (may result in a relocation entry). */
static void
out_inc_line_addr (int line_delta, addressT addr_delta);
static void
out_set_addr (symbolS *sym)
{
expressionS exp;
addressT expr_addr, expr_addr_aligned;
memset (&exp, 0, sizeof exp);
out_opcode (DW_LNS_extended_op);
out_uleb128 (sizeof_address + 1);
out_opcode (DW_LNE_set_address);
/* The expression at the bottom must be aligned to OCTETS_PER_BYTE. The
statements after the for loop will contribute 3 more octets. */
expr_addr = frag_now_fix_octets () + 3;
expr_addr_aligned = (expr_addr + OCTETS_PER_BYTE - 1) & -OCTETS_PER_BYTE;
for ( ; expr_addr != expr_addr_aligned; expr_addr++)
out_inc_line_addr (0, 0); /* NOP */
out_opcode (DW_LNS_extended_op); /* 1 octet */
out_uleb128 (sizeof_address + 1); /* 1 octet */
out_opcode (DW_LNE_set_address); /* 1 octet */
exp.X_op = O_symbol;
exp.X_add_symbol = sym;
exp.X_add_number = 0;