Skip to content

[AAELF64] Simplify expressions used for relative relocations #337

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
pcc wants to merge 1 commit into
base: main
Choose a base branch
from
Open

[AAELF64] Simplify expressions used for relative relocations #337

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 3 additions & 5 deletions aaelf64-morello/aaelf64-morello.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -480,10 +480,8 @@ The following nomenclature is used in the descriptions of relocation operations:
the second entry holds a platform-specific offset or pointer. The pair of
pointer-sized entries will be relocated with ``R_MORELLO_TLSDESC(S+A)``.

- ``Delta(S)`` if ``S`` is a normal symbol, resolves to the difference between the
static link address of ``S`` and the execution address of ``S``. If ``S`` is the
null symbol (ELF symbol index 0), resolves to the difference between the static
link address of ``P`` and the execution address of ``P``.
- ``Delta`` resolves to the difference between the static link address of
``P`` and the execution address of ``P``.

- ``TPREL(S)`` resolves to a pair of two 64-bit values. The first value
contains the offset in the static TLS block of the thread-local symbol ``S``.
Expand Down Expand Up @@ -728,7 +726,7 @@ Dynamic Morello relocations
| 59400 | ``R_MORELLO_FUNC_RELATIVE`` | ``CAP_INIT(S, A, CAP_SIZE, CAP_PERM)`` | See note below. |
| | | | |
+-------+-----------------------------+-----------------------------------------+------------------------------------------+
| 59401 | ``R_AARCH64_FUNC_RELATIVE`` | ``Delta(S) + A`` | See note below. |
| 59401 | ``R_AARCH64_FUNC_RELATIVE`` | ``Delta + A`` | See note below. |
| | | | |
+-------+-----------------------------+-----------------------------------------+------------------------------------------+

Expand Down
10 changes: 5 additions & 5 deletions aaelf64/aaelf64.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1051,7 +1051,7 @@ The following nomenclature is used in the descriptions of relocation operations:

- ``G(expr)`` is the address of the GOT entry for the expression expr.

- ``Delta(S)`` if ``S`` is a normal symbol, resolves to the difference between the static link address of ``S`` and the execution address of ``S``. If ``S`` is the null symbol (ELF symbol index 0), resolves to the difference between the static link address of ``P`` and the execution address of ``P``.
- ``Delta`` resolves to the difference between the static link address of ``P`` and the execution address of ``P``.

- ``Indirect(expr)`` represents the result of calling expr as a function. The result is the return value from the function that is returned in ``r0``. The arguments passed to the function are defined by the platform ABI.

Expand Down Expand Up @@ -1802,7 +1802,7 @@ The dynamic relocations for those execution environments that support only a lim
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1026 | 182 | R\_<CLS>\_JUMP\_SLOT | S + A | See note below |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1027 | 183 | R\_<CLS>\_RELATIVE | Delta(S) + A | See note below |
| 1027 | 183 | R\_<CLS>\_RELATIVE | Delta + A | See note below |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1028 | 184 | R\_<CLS>\_TLS\_IMPDEF1 | | See note below |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
Expand All @@ -1816,9 +1816,9 @@ The dynamic relocations for those execution environments that support only a lim
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1031 | 187 | R\_<CLS>\_TLSDESC | TLSDESC(S+A) | Identifies a TLS descriptor to be filled |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1032 | 188 | R\_<CLS>\_IRELATIVE | Indirect(Delta(S) + A) | See note below. |
| 1032 | 188 | R\_<CLS>\_IRELATIVE | Indirect(Delta + A) | See note below. |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1041 | \- | R\_<CLS>\_AUTH\_RELATIVE | SIGN(DELTA(S) + A, SCHEMA(\*P)) | See note below. |
| 1041 | \- | R\_<CLS>\_AUTH\_RELATIVE | SIGN(Delta + A, SCHEMA(\*P)) | See note below. |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
| 1042 | \- | R\_AARCH64\_AUTH\_GLOB\_DAT | SIGN((S + A), SCHEMA(\*P)) | See note below. |
+------------+------------+-----------------------------+------------------------------------+-------------------------------------------+
Expand Down Expand Up @@ -1849,7 +1849,7 @@ The need for copy relocations can be avoided if a compiler generates all code re

- Because the initial value of the place is not related to the ultimate target of a ``R_<CLS>_JUMP_SLOT`` relocation the addend ``A`` of such a REL-type relocation shall be zero rather than the initial content of the place. A platform ABI shall prescribe whether or not the ``r_addend`` field of such a RELA-type relocation is honored. (There may be security-related reasons not to do so).

``R_<CLS>_RELATIVE`` represents a relative adjustment to the place based on the load address of the object relative to its original link address. All symbols defined in the same segment will have the same relative adjustment. If ``S`` is the null symbol (ELF symbol index 0) then the adjustment is based on the segment defining the place. On systems where all segments are mapped contiguously the adjustment will be the same for each relocation, thus adjustment never needs to resolve the symbol. This relocation represents an optimization; a static linker can use it to replace ``R_<CLS>_GLOB_DAT`` when the symbol is known at static link time to always resolve to the current link unit.
``R_<CLS>_RELATIVE`` represents a relative adjustment to the place based on the load address of the object relative to its original link address. All symbols defined in the same binary will have the same relative adjustment. This relocation represents an optimization; a static linker can use it to replace ``R_<CLS>_GLOB_DAT`` when the symbol is known at static link time to always resolve to the current link unit.

``R_<CLS>_IRELATIVE`` represents a dynamic selection of the place’s resolved value. The means by which this relocation is generated is platform specific, as are the conditions that must hold when resolving takes place.

Expand Down
2 changes: 1 addition & 1 deletion memtagabielf64/memtagabielf64.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -638,7 +638,7 @@ The relocations reference the following mnemonics:
+------------+--------------------+----------------+-------------------------------+
| 1025 | R_AARCH64_GLOB_DAT | S + A | LDG(S) + A |
+------------+--------------------+----------------+-------------------------------+
| 1027 | R_AARCH64_RELATIVE | Delta(S) + A | LDG(Delta(S) + A + \*P) - \*P |
| 1027 | R_AARCH64_RELATIVE | Delta + A | LDG(Delta + A + \*P) - \*P |
+------------+--------------------+----------------+-------------------------------+

``R_AARCH64_ABS64`` and ``R_AARCH64_GLOB_DAT`` are thus extended to materialize
Expand Down
2 changes: 1 addition & 1 deletion pauthabielf64/pauthabielf64.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -744,7 +744,7 @@ relocation.
+====================+==============================+====================================+
| 0x244 (580) | R\_AARCH64\_AUTH\_ABS64 | SIGN(S + A, SCHEMA(\*P)) |
+--------------------+------------------------------+------------------------------------+
| 0x411 (1041) | R\_AARCH64\_AUTH\_RELATIVE | SIGN(DELTA(S) + A, SCHEMA(\*P)) |
| 0x411 (1041) | R\_AARCH64\_AUTH\_RELATIVE | SIGN(DELTA + A, SCHEMA(\*P)) |
+--------------------+------------------------------+------------------------------------+

.. raw:: pdf
Expand Down