Summary:
Currently when --no-rosegment is specified or a linker script with SECTIONS command is used,
.rodata (A) .text (AX) are assigned the same rank and .rodata may be placed after .text .
This increases the gap between .text and .bss and can cause pc-relative relocation overflow (e.g. gcc crtbegin.o crtbegin.S have R_X86_64_PC32 relocation from .text to .bss).
This patch makes SingleRoRx affect only segment layout, not section layout. As a consequence, .rodata will be placed before .text regardless of SingleRoRx.
Reviewers: espindola, ruiu, grimar, echristo, javed.absar
Subscribers: emaste, arichardson, llvm-commits
Differential Revision: https://reviews.llvm.org/D48405
llvm-svn: 335627
* Move `REQUIRES:` line to the top
* llvm-mc ... -o %t -> llvm-mc ... -o %t.o
* Don't check "TEXT" "DATA" columns (they are bfd-style names that do
not fit into llvm well) in llvm-objdump output
llvm-svn: 335498
The ARM.exidx section contains a table of 8-byte entries with the first
word of each entry an offset to the function it describes and the second
word instructions for unwinding if an exception is thrown from that
function. The SHF_LINK_ORDER processing will order the table in ascending
order of the functions described by the exception table entries. As the
address range of an exception table entry is terminated by the next table
entry, it is possible to merge consecutive table entries that have
identical unwind instructions.
For this implementation we define a table entry to be identical if:
- Both entries are the special EXIDX_CANTUNWIND.
- Both entries have the same inline unwind instructions.
We do not attempt to establish if table entries that are references to
.ARM.extab sections are identical.
This implementation works at a granularity of a single .ARM.exidx
InputSection. If all entries in the InputSection are identical to the
previous table entry we can remove the InputSection. A more sophisticated
but more complex implementation would rewrite InputSection contents so that
duplicates within a .ARM.exidx InputSection can be merged.
Differential Revision: https://reviews.llvm.org/D40967
llvm-svn: 320803
The .ARM.exidx table has an entry for each function with the first entry
giving the start address of the function, the table is sorted in ascending
order of function address. Given a PC value, the unwinder will search the
table for the entry that contains the PC value.
If the table entry happens to be the last, the range of the addresses that
the final unwinding table describes will extend to the end of the address
space. To prevent an incorrect address outside the address range of the
program matching the last entry we follow ld.bfd's example and add a
sentinel EXIDX_CANTUNWIND entry at the end of the table. This gives the
final real table entry an upper bound.
In addition the llvm libunwind unwinder currently depends on the presence
of a sentinel entry (PR31091).
Differential revision: https://reviews.llvm.org/D26977
llvm-svn: 287869
Fangrui Song