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llext: basic x86 support
Adds basic x86 support for LLEXT. Signed-off-by: Lauren Murphy <[email protected]>
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7 files changed

+189
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‎arch/x86/core/CMakeLists.txt

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Original file line numberDiff line numberDiff line change
@@ -27,6 +27,8 @@ zephyr_library_sources_ifdef(CONFIG_X86_VERY_EARLY_CONSOLE early_serial.c)
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zephyr_library_sources_ifdef(CONFIG_THREAD_LOCAL_STORAGE tls.c)
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zephyr_library_sources_ifdef(CONFIG_LLEXT elf.c)
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if(CONFIG_X86_64)
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include(intel64.cmake)
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else()

‎arch/x86/core/elf.c

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@@ -0,0 +1,142 @@
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/*
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* Copyright (c) 2025 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/llext/elf.h>
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#include <zephyr/llext/llext.h>
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#include <zephyr/llext/llext_internal.h>
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#include <zephyr/llext/loader.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(elf, CONFIG_LLEXT_LOG_LEVEL);
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#ifdef CONFIG_64BIT
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#define R_X86_64_64 1
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#define R_X86_64_PC32 2
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#define R_X86_64_PLT32 4
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#define R_X86_64_32 10
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#define R_X86_64_32S 11
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/**
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* @brief Architecture specific function for relocating shared elf
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*
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* Elf files contain a series of relocations described in multiple sections.
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* These relocation instructions are architecture specific and each architecture
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* supporting modules must implement this.
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*
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* The relocation codes are well documented:
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*
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* https://refspecs.linuxfoundation.org/elf/x86_64-abi-0.95.pdf (intel64)
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*/
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int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
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const elf_shdr_t *shdr)
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{
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int ret = 0;
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const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
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elf_sym_t sym;
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uintptr_t sym_base_addr;
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const char *sym_name;
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ret = llext_read_symbol(ldr, ext, rel, &sym);
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if (ret != 0) {
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LOG_ERR("Could not read symbol from binary!");
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return ret;
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}
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sym_name = llext_symbol_name(ldr, ext, &sym);
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ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
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if (ret != 0) {
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LOG_ERR("Could not find symbol %s!", sym_name);
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return ret;
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}
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sym_base_addr += rel->r_addend;
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int reloc_type = ELF32_R_TYPE(rel->r_info);
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switch (reloc_type) {
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case R_X86_64_PC32:
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case R_X86_64_PLT32:
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*(uint32_t *)loc = sym_base_addr - loc;
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break;
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case R_X86_64_64:
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case R_X86_64_32:
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case R_X86_64_32S:
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*(uint32_t *)loc = sym_base_addr;
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break;
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default:
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LOG_ERR("unknown relocation: %u\n", reloc_type);
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ret = -ENOEXEC;
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break;
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}
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return ret;
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}
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#else
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#define R_386_32 1
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#define R_286_PC32 2
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/**
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* @brief Architecture specific function for relocating shared elf
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*
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* Elf files contain a series of relocations described in multiple sections.
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* These relocation instructions are architecture specific and each architecture
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* supporting modules must implement this.
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*
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* The relocation codes are well documented:
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*
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* https://docs.oracle.com/cd/E19683-01/817-3677/chapter6-26/index.html (ia32)
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*/
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int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
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const elf_shdr_t *shdr)
97+
{
98+
int ret = 0;
99+
const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
100+
elf_sym_t sym;
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uintptr_t sym_base_addr;
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const char *sym_name;
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/* x86 uses elf_rel_t records with no addends */
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uintptr_t addend = *(uintptr_t *)loc;
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ret = llext_read_symbol(ldr, ext, rel, &sym);
108+
109+
if (ret != 0) {
110+
LOG_ERR("Could not read symbol from binary!");
111+
return ret;
112+
}
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sym_name = llext_symbol_name(ldr, ext, &sym);
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ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
117+
118+
if (ret != 0) {
119+
LOG_ERR("Could not find symbol %s!", sym_name);
120+
return ret;
121+
}
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sym_base_addr += addend;
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int reloc_type = ELF32_R_TYPE(rel->r_info);
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switch (reloc_type) {
128+
case R_386_32:
129+
*(uint32_t *)loc = sym_base_addr;
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break;
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case R_286_PC32:
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*(uint32_t *)loc = sym_base_addr - loc;
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break;
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default:
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LOG_ERR("unknown relocation: %u\n", reloc_type);
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ret = -ENOEXEC;
137+
break;
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}
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return ret;
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}
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#endif

‎cmake/compiler/gcc/target_x86.cmake

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@@ -15,6 +15,28 @@ else()
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endif()
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endif()
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# Flags not supported by llext linker
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# (regexps are supported and match whole word)
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set(LLEXT_REMOVE_FLAGS
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-fno-pic
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-fno-pie
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-ffunction-sections
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-fdata-sections
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-g.*
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-Os
27+
)
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# Force compiler and linker match
30+
if(CONFIG_X86_64)
31+
set(LLEXT_APPEND_FLAGS
32+
-m64
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)
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else()
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set(LLEXT_APPEND_FLAGS
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-m32
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)
38+
endif()
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# GNU Assembler, by default on non-Linux targets, treats slashes as
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# start of comments on i386.
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# (https://sourceware.org/binutils/docs-2.33.1/as/i386_002dChars.html#i386_002dChars)

‎subsys/llext/llext_link.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -389,7 +389,7 @@ static void llext_link_plt(struct llext_loader *ldr, struct llext *ext, elf_shdr
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int llext_link(struct llext_loader *ldr, struct llext *ext, const struct llext_load_param *ldr_parm)
390390
{
391391
uintptr_t sect_base = 0;
392-
elf_rela_t rel;
392+
elf_rela_t rel = {0};
393393
elf_word rel_cnt = 0;
394394
const char *name;
395395
int i, ret;

‎tests/subsys/llext/no_mem_protection.conf

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Original file line numberDiff line numberDiff line change
@@ -7,3 +7,4 @@ CONFIG_ARM_MPU=n
77
CONFIG_ARM_AARCH32_MMU=n
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CONFIG_RISCV_PMP=n
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CONFIG_ARC_MPU_ENABLE=n
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CONFIG_X86_MMU=n

‎tests/subsys/llext/src/syscalls_ext.c

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Original file line numberDiff line numberDiff line change
@@ -8,12 +8,25 @@
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* This code demonstrates syscall support.
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*/
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/* This include directive must appear first in the file.
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*
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* On x86 platforms with demand paging on, Zephyr generates a
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* .pinned_text section containing syscalls. The LLEXT loader
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* requires .text-like sections to appear close to .text at the
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* start of the object file, before .rodata, so they can be
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* grouped into a contiguous text region.
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*
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* Including syscalls_ext.h first ensures the first instance of
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* data to be placed in .pinned_text appears before the first instance
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* of data for .rodata. As a result, .pinned_text will appear
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* before .rodata.
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*/
24+
#include "syscalls_ext.h"
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1126
#include <zephyr/llext/symbol.h>
1227
#include <zephyr/sys/printk.h>
1328
#include <zephyr/ztest_assert.h>
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15-
#include "syscalls_ext.h"
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void test_entry(void)
1831
{
1932
int input = 41;

‎tests/subsys/llext/testcase.yaml

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@@ -39,6 +39,7 @@ tests:
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- arm
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- riscv
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- arc
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- x86
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filter: not CONFIG_MPU and not CONFIG_MMU
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extra_conf_files: ['no_mem_protection.conf']
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extra_configs:
@@ -56,6 +57,7 @@ tests:
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- arm64
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- arm
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- riscv
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- x86
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filter: CONFIG_MMU or CONFIG_RISCV_PMP
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integration_platforms:
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- qemu_cortex_a53 # ARM Cortex-A53 (ARMv8-A ISA)
@@ -68,6 +70,7 @@ tests:
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- xtensa
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- riscv
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- arc
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- x86
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integration_platforms:
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- qemu_xtensa/dc233c # Xtensa ISA
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filter: not CONFIG_MPU and not CONFIG_MMU
@@ -80,6 +83,7 @@ tests:
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- xtensa
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- riscv
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- arc
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- x86
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platform_exclude:
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- qemu_arc/qemu_arc_hs5x # See #80949
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- nsim/nsim_hs5x # See #80949
@@ -101,6 +105,7 @@ tests:
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- xtensa
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- riscv
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- arc
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- x86
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integration_platforms:
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- qemu_xtensa/dc233c # Xtensa ISA
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filter: not CONFIG_MPU and not CONFIG_MMU
@@ -114,6 +119,7 @@ tests:
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- xtensa
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- riscv
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- arc
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- x86
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platform_exclude:
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- qemu_arc/qemu_arc_hs5x # See #80949
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- nsim/nsim_hs5x # See #80949

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