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Add Auth variants of TLSDESC generating GOT relocations
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Add static Auth equivalents of the existing relocations:
* R_AARCH64_TLSDESC_ADR_PAGE21
* R_AARCH64_TLSDESC_LD64_LO12
* R_AARCH64_TLSDESC_ADD_LO12

These are sufficient to implement the small code-model for TLSDESC
using the PAuthABI. Support for the tiny and large code-model is
not implemented for the PAuthABI, or for the normal ABI in both
clang and GCC so we defer from specifiying Auth variants of all
possible relocations.

I've followed the convention that non-zero addends are not
permitted for GOT generating relocations. As each unique S+A
combination needs its own pair of GOT slots indexed by S+A and
no static linker supports that.

Fixes ARM-software#293
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@smithp35
smithp35 committed Nov 29, 2024
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155 changes: 86 additions & 69 deletions pauthabielf64/pauthabielf64.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -243,6 +243,9 @@ changes to the content of the document for that release.
| | | - Add R_AARCH64_AUTH_GOT_ADR_PREL_LO21 relocation. |
| | | - Remove addend in GDAT relocation operation. |
+------------+-----------------------------+------------------------------------------------------------------+
| 2024Q1 | 5\ :sup:`th` November 2024 | - Add static Auth TLSDESC generating relocations |
| | | - Correct comment entry for R_AARCH64_AUTH_LD64_GOTOFF_LO15 |
+------------+-----------------------------+------------------------------------------------------------------+

References
----------
Expand Down Expand Up @@ -1103,80 +1106,94 @@ AUTH variant GOT Generating Relocations
``ENCD(value)`` is the encoding of the signing schema into the GOT
slot using the ``IA`` key for symbols of type STT_FUNC and the ``DA``
key for all other symbol types. The address of the GOT slot ``G`` is
used as a modifer.
used as a modifer. For ``ENCD(GTLSDESC(S)`` the encoding applies to
the first entry containing the pointer to the variable's TLS
descriptor resolver function.

The GOT entries must be relocated by AUTH variant dynamic relocations.

.. table:: PAuth GOT generating relocations

+-------------+----------------------------------------+----------------------------------+--------------------------+
| ELF 64 Code | Name | Operation | Comment |
+=============+========================================+==================================+==========================+
| 0x8110 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G0 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [15:0] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8111 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G0\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [15:0] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8112 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G1 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [31:16] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8113 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G1\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [31:16] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8114 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G2 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [47:32] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8115 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G2\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [47:32] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8116 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G3 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [63:48] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8117 | R\_AARCH64\_AUTH\_GOT\_LD\_PREL19 | G(ENCD(GDAT(S))) - P | Set a load-literal im- |
| | | | mediate field to bits |
| | | | [20:2] of X; check |
| | | | –2\ :sup:`20` <= |
| | | | X < 2 \ :sup:`20` |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8118 | R\_AARCH64\_AUTH\_LD64\_GOTOFF\_LO15 | G(ENCD(GDAT(S))) - GOT | Set the immediate |
| | | | value of an ADRP |
| | | | to bits [32:12] of X; |
| | | | check that –2\ :sup:`32` |
| | | | <= X < 2\ :sup:`32` |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x8119 | R\_AARCH64\_AUTH\_ADR\_GOT\_PAGE | G(ENCD(GDAT(S))) - Page(P) | Set the immediate |
| | | | value of an ADRP |
| | | | to bits [32:12] of X; |
| | | | check that –2\ :sup:`32` |
| | | | <= X < 2\ :sup:`32` |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x811A | R\_AARCH64\_AUTH\_LD64\_GOT\_LO12_NC | G(ENCD(GDAT(S))) | Set the LD/ST immediate |
| | | | field to bits [11:3] of |
| | | | X. No overflow check; |
| | | | check that X&7 = 0 |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x811B | R\_AARCH64\_AUTH\_LD64\_GOTPAGE\_LO15 | G(ENCD(GDAT(S))) - Page(GOT) | Set the LD/ST immediate |
| | | | field to bits [14:3] of |
| | | | X; check that 0 <= X < |
| | | | 2\ :sup:`15` |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x811C | R\AARCH64\_AUTH\_GOT\_ADD_LO12_NC | G(ENCD(GDAT(S))) | Set an ADD immediate |
| | | | value to bits [11:0] of |
| | | | X. No overflow check. |
+-------------+----------------------------------------+----------------------------------+--------------------------+
| 0x811D | R\AARCH64\_AUTH\_GOT\_ADR\_PREL\_LO21 | G(ENCD(GDAT(S))) - P | Set the immediate |
| | | | value to bits[20:0] of X;|
| | | | check that -2 :sup:`20` |
| | | | <= 2 :sup: `20` |
+-------------+----------------------------------------+----------------------------------+--------------------------+
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| ELF 64 Code | Name | Operation | Comment |
+=============+========================================+========================================+==========================+
| 0x8110 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G0 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [15:0] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8111 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G0\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [15:0] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8112 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G1 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [31:16] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8113 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G1\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [31:16] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8114 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G2 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [47:32] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8115 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G2\_NC | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [47:32] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8116 | R\_AARCH64\_AUTH\_MOVW\_GOTOFF\_G3 | G(ENCD(GDAT(S))) - GOT | Set a MOV[NZ] immediate |
| | | | field to bits [63:48] of |
| | | | X (see notes below) |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8117 | R\_AARCH64\_AUTH\_GOT\_LD\_PREL19 | G(ENCD(GDAT(S))) - P | Set a load-literal im- |
| | | | mediate field to bits |
| | | | [20:2] of X; check |
| | | | –2\ :sup:`20` <= |
| | | | X < 2 \ :sup:`20` |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8118 | R\_AARCH64\_AUTH\_LD64\_GOTOFF\_LO15 | G(ENCD(GDAT(S))) - GOT | Set a LD/ST immediate |
| | | | field to bits [14:3] of |
| | | | X. check that 0 <= X < |
| | | | 2\ :sup:`15`, X&7 = 0 |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8119 | R\_AARCH64\_AUTH\_ADR\_GOT\_PAGE | G(ENCD(GDAT(S))) - Page(P) | Set the immediate |
| | | | value of an ADRP |
| | | | to bits [32:12] of X; |
| | | | check that –2\ :sup:`32` |
| | | | <= X < 2\ :sup:`32` |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811A | R\_AARCH64\_AUTH\_LD64\_GOT\_LO12_NC | G(ENCD(GDAT(S))) | Set the LD/ST immediate |
| | | | field to bits [11:3] of |
| | | | X. No overflow check; |
| | | | check that X&7 = 0 |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811B | R\_AARCH64\_AUTH\_LD64\_GOTPAGE\_LO15 | G(ENCD(GDAT(S))) - Page(GOT) | Set the LD/ST immediate |
| | | | field to bits [14:3] of |
| | | | X; check that 0 <= X < |
| | | | 2\ :sup:`15` |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811C | R\_AARCH64\_AUTH\_GOT\_ADD_LO12_NC | G(ENCD(GDAT(S))) | Set an ADD immediate |
| | | | value to bits [11:0] of |
| | | | X. No overflow check. |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811D | R\_AARCH64\_AUTH\_GOT\_ADR\_PREL\_LO21 | G(ENCD(GDAT(S))) - P | Set the immediate |
| | | | value to bits[20:0] of X;|
| | | | check that -2 :sup:`20` |
| | | | <= 2 :sup: `20` |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811E | R\_AARCH64\_AUTH\_TLSDESC\_ADR\_PAGE21 | Page(G(ENCD(GTLSDESC(S)))) - Page(P) | Set an ADRP immediate |
| | | | field to bits [32:12] of |
| | | | X; check –2\ :sup:`20` |
| | | | <= X < 2 \ :sup:`20` |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x811F | R\_AARCH64\_AUTH\_TLSDESC\_LD64\_LO12 | G(ENCD(GTLSDESC(S))) | Set an LD offset to bits |
| | | | [11:3] of X. No overflow |
| | | | check; check X&7 = 0. |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
| 0x8120 | R\_AARCH64\_AUTH\_TLSDESC\_ADD\_LO12 | G(ENCD(GTLSDESC(S))) | Set an ADD immediate |
| | | | field to bits [11:0] of |
| | | | X. No overflow check. |
+-------------+----------------------------------------+----------------------------------------+--------------------------+
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