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nuttx/include/elf.h
Marco Casaroli 1aa32bbc07 libs/libc/elf: Place an FDPIC object's segments independently. 
An ET_DYN object is loaded into one allocation with its data behind its
text, because its data references sit at a fixed distance from the code
that makes them.  An FDPIC object does not work that way: it reaches its
data through a base register, so the two segments can be placed wherever
suits, and the point of the format is that the read-only one is left on
the media and executed there while only the writable one is copied.  One
copy of the text then serves every instance.

So libelf_load() grows a second case.  The object announces itself in the
OS/ABI byte, which is noted once in libelf_loadhdrs() rather than
re-derived; e_flags cannot be used for this, as an FDPIC object's are an
unremarkable EABI version and testing them would reject every valid
module.  Text is taken from the media address plus the segment's own file
offset -- the same arithmetic the ET_REL path already does with
sh_offset -- and libelf_loadfile() does not read it.  If the filesystem
cannot show its media, the loader copies the text to RAM instead.  The
module then loses the shared text and the flash saving, but it runs.

Obtaining that address needs two mechanisms, and they are not
interchangeable.  A compacting filesystem can move a file's blocks, so it
hands out an address only with a pin that holds them still and expects
the pin back; xipfs is the one in tree.  A filesystem whose layout never
changes has nothing to hold and answers FIOC_XIPBASE with a bare address;
romfs and tmpfs are those.  libelf_xipacquire() asks for the pin first,
because a filesystem that needs one is not safe without it, and
libelf_unload() gives it back.  The loader asks for a pin only if it can
hold one, or the pin would stay for ever.

The pin is thus not specific to FDPIC.  Any module that executes in place
from a compacting filesystem takes one, and gives it back at unload.

mmap() is not used, though both filesystems implement it.  The mapping
would be recorded against whichever task called the loader, while the
release happens when the module's own task exits, which is a different
group -- so the pin would outlive the module and the extent would never
become movable again.

Unloading has to change with placement: the existing path frees only
textalloc because ET_DYN had a single allocation, which would leak an
FDPIC object's data and free media the filesystem only lent us.

Nothing here runs for a non-FDPIC object; every branch is behind the flag
and the single-allocation path is untouched.  Built and booted
mps3-an547:picostest, which is CONFIG_ELF with CONFIG_PIC, with no change
in behaviour.

Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
2026-09-08 16:31:16 -03:00

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/****************************************************************************
* include/elf.h
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
#ifndef __INCLUDE_ELF_H
#define __INCLUDE_ELF_H
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#define EI_NIDENT 16 /* Size of e_ident[] */
/* NOTE: elf64.h and elf32.h refer EI_NIDENT defined above */
#ifdef CONFIG_ARCH_64BIT
# include <elf64.h>
#else
# include <elf32.h>
#endif
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Values for Elf_Ehdr::e_type */
#define ET_NONE 0 /* No file type */
#define ET_REL 1 /* Relocatable file */
#define ET_EXEC 2 /* Executable file */
#define ET_DYN 3 /* Shared object file */
#define ET_CORE 4 /* Core file */
#define ET_LOPROC 0xff00 /* Processor-specific */
#define ET_HIPROC 0xffff /* Processor-specific */
/* Values for Elf_Ehdr::e_machine (most of this were not included in the
* original SCO document but have been gleaned from elsewhere).
*/
#define EM_NONE 0 /* No machine */
#define EM_M32 1 /* AT&T WE 32100 */
#define EM_SPARC 2 /* SPARC */
#define EM_386 3 /* Intel 80386 */
#define EM_68K 4 /* Motorola 68000 */
#define EM_88K 5 /* Motorola 88000 */
#define EM_486 6 /* Intel 486+ */
#define EM_860 7 /* Intel 80860 */
#define EM_MIPS 8 /* MIPS R3000 Big-Endian */
#define EM_MIPS_RS4_BE 10 /* MIPS R4000 Big-Endian */
#define EM_PARISC 15 /* HPPA */
#define EM_SPARC32PLUS 18 /* Sun's "v8plus" */
#define EM_PPC 20 /* PowerPC */
#define EM_PPC64 21 /* PowerPC64 */
#define EM_ARM 40 /* ARM */
#define EM_SH 42 /* SuperH */
#define EM_SPARCV9 43 /* SPARC v9 64-bit */
#define EM_H8_300 46
#define EM_IA_64 50 /* HP/Intel IA-64 */
#define EM_X86_64 62 /* AMD x86-64 */
#define EM_S390 22 /* IBM S/390 */
#define EM_CRIS 76 /* Axis Communications 32-bit embedded processor */
#define EM_V850 87 /* NEC v850 */
#define EM_M32R 88 /* Renesas M32R */
#define EM_XTENSA 94 /* Tensilica Xtensa */
#define EM_AARCH64 183 /* ARM-64 Architecture */
#define EM_RISCV 243 /* RISC-V */
#define EM_ALPHA 0x9026
#define EM_CYGNUS_V850 0x9080
#define EM_CYGNUS_M32R 0x9041
#define EM_S390_OLD 0xa390
#define EM_FRV 0x5441
/* Values for Elf_Ehdr::e_version */
#define EV_NONE 0 /* Invalid version */
#define EV_CURRENT 1 /* The current version */
/* Table 2. Ehe ELF identifier */
#define EI_MAG0 0 /* File identification */
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4 /* File class */
#define EI_DATA 5 /* Data encoding */
#define EI_VERSION 6 /* File version */
#define EI_OSABI 7 /* OS ABI */
#define EI_PAD 8 /* Start of padding bytes */
/* EI_NIDENT is defined in "Included Files" section */
#define EI_MAGIC_SIZE 4
#define EI_MAGIC {0x7f, 'E', 'L', 'F'}
#define ELFMAG0 0x7f /* EI_MAG */
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'
#define ELFMAG "\177ELF"
/* Table 3. Values for EI_CLASS */
#define ELFCLASSNONE 0 /* Invalid class */
#define ELFCLASS32 1 /* 32-bit objects */
#define ELFCLASS64 2 /* 64-bit objects */
/* Table 4. Values for EI_DATA */
#define ELFDATANONE 0 /* Invalid data encoding */
#define ELFDATA2LSB 1 /* Least significant byte occupying the lowest address */
#define ELFDATA2MSB 2 /* Most significant byte occupying the lowest address */
/* Table 6. Values for EI_OSABI */
#define ELFOSABI_NONE 0 /* UNIX System V ABI */
#define ELFOSABI_SYSV 0 /* Alias. */
#define ELFOSABI_HPUX 1 /* HP-UX */
#define ELFOSABI_NETBSD 2 /* NetBSD. */
#define ELFOSABI_GNU 3 /* Object uses GNU ELF extensions. */
#define ELFOSABI_LINUX ELFOSABI_GNU
/* Compatibility alias. */
#define ELFOSABI_SOLARIS 6 /* Sun Solaris. */
#define ELFOSABI_AIX 7 /* IBM AIX. */
#define ELFOSABI_IRIX 8 /* SGI Irix. */
#define ELFOSABI_FREEBSD 9 /* FreeBSD. */
#define ELFOSABI_TRU64 10 /* Compaq TRU64 UNIX. */
#define ELFOSABI_MODESTO 11 /* Novell Modesto. */
#define ELFOSABI_OPENBSD 12 /* OpenBSD. */
#define ELFOSABI_ARM_AEABI 64 /* ARM EABI */
#define ELFOSABI_ARM_FDPIC 65 /* ARM FDPIC */
#define ELFOSABI_ARM 97 /* ARM */
#define ELFOSABI_STANDALONE 255 /* Standalone (embedded) application */
#ifndef ELF_OSABI
#define ELF_OSABI ELFOSABI_NONE
#endif
/* Table 7: Special Section Indexes */
#define SHN_UNDEF 0
#define SHN_LOPROC 0xff00
#define SHN_HIPROC 0xff1f
#define SHN_ABS 0xfff1
#define SHN_COMMON 0xfff2
/* Figure 4-9: Section Types, sh_type */
#define SHT_NULL 0
#define SHT_PROGBITS 1
#define SHT_SYMTAB 2
#define SHT_STRTAB 3
#define SHT_RELA 4
#define SHT_HASH 5
#define SHT_DYNAMIC 6
#define SHT_NOTE 7
#define SHT_NOBITS 8
#define SHT_REL 9
#define SHT_SHLIB 10
#define SHT_DYNSYM 11
#define SHT_INIT_ARRAY 14
#define SHT_FINI_ARRAY 15
#define SHT_PREINIT_ARRAY 16
#define SHT_LOPROC 0x70000000
#define SHT_HIPROC 0x7fffffff
#define SHT_LOUSER 0x80000000
#define SHT_HIUSER 0xffffffff
/* Figure 4-11: Section Attribute Flags, sh_flags */
#define SHF_WRITE 1
#define SHF_ALLOC 2
#define SHF_EXECINSTR 4
#define SHF_INFO_LINK 0x40
#define SHF_MASKPROC 0xf0000000
/* Figure 4-16: Symbol Binding, ELF_ST_BIND */
#define STB_LOCAL 0
#define STB_GLOBAL 1
#define STB_WEAK 2
#define STB_LOPROC 13
#define STB_HIPROC 15
/* Figure 4-17: Symbol Types, ELF_ST_TYPE */
#define STT_NOTYPE 0
#define STT_OBJECT 1
#define STT_FUNC 2
#define STT_SECTION 3
#define STT_FILE 4
#define STT_LOPROC 13
#define STT_HIPROC 15
/* Table 7-21 ELF Symbol Visibility */
#define STV_DEFAULT 0
#define STV_INTERNAL 1
#define STV_HIDDEN 2
#define STV_PROTECTED 3
/* Figure 5-2: Segment Types, p_type */
#define PT_NULL 0
#define PT_LOAD 1
#define PT_DYNAMIC 2
#define PT_INTERP 3
#define PT_NOTE 4
#define PT_SHLIB 5
#define PT_PHDR 6
/* GCC specific */
#define PT_GNU_EH_FRAME 0x6474e550 /* GCC exception handler frame */
#define PT_GNU_STACK 0x6474e551 /* Stack executability */
#define PT_GNU_RELRO 0x6474e552 /* Read-only after relocation */
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff
/* Figure 5-3: Segment Flag Bits, p_flags */
#define PF_X 1 /* Execute */
#define PF_W 2 /* Write */
#define PF_R 4 /* Read */
#define PF_MASKOS 0x0ff00000 /* All bits included in the PF_MASKOS
* mask are reserved for operating system-specific
* semantics.
*/
#define PF_REGISTER 0x00100000 /* Register, need pointer aligned access */
#define PF_MASKPROC 0xf0000000 /* Unspecified */
/* Figure 5-10: Dynamic Array Tags, d_tag */
#define DT_NULL 0 /* d_un=ignored */
#define DT_NEEDED 1 /* d_un=d_val */
#define DT_PLTRELSZ 2 /* d_un=d_val */
#define DT_PLTGOT 3 /* d_un=d_ptr */
#define DT_HASH 4 /* d_un=d_ptr */
#define DT_STRTAB 5 /* d_un=d_ptr */
#define DT_SYMTAB 6 /* d_un=d_ptr */
#define DT_RELA 7 /* d_un=d_ptr */
#define DT_RELASZ 8 /* d_un=d_val */
#define DT_RELAENT 9 /* d_un=d_val */
#define DT_STRSZ 10 /* d_un=d_val */
#define DT_SYMENT 11 /* d_un=d_val */
#define DT_INIT 12 /* d_un=d_ptr */
#define DT_FINI 13 /* d_un=d_ptr */
#define DT_SONAME 14 /* d_un=d_val */
#define DT_RPATH 15 /* d_un=d_val */
#define DT_SYMBOLIC 16 /* d_un=ignored */
#define DT_REL 17 /* d_un=d_ptr */
#define DT_RELSZ 18 /* d_un=d_val */
#define DT_RELENT 19 /* d_un=d_val */
#define DT_PLTREL 20 /* d_un=d_val */
#define DT_DEBUG 21 /* d_un=d_ptr */
#define DT_TEXTREL 22 /* d_un=ignored */
#define DT_JMPREL 23 /* d_un=d_ptr */
#define DT_BINDNOW 24 /* d_un=ignored */
#define DT_LOPROC 0x70000000 /* d_un=unspecified */
#define DT_HIPROC 0x7fffffff /* d_un= unspecified */
/* Legal values for note segment descriptor types for core files. */
#define NT_PRSTATUS 1 /* Contains copy of prstatus struct */
#define NT_PRFPREG 2 /* Contains copy of fpregset struct. */
#define NT_FPREGSET 2 /* Contains copy of fpregset struct */
#define NT_PRPSINFO 3 /* Contains copy of prpsinfo struct */
#define NT_PRXREG 4 /* Contains copy of prxregset struct */
#define NT_TASKSTRUCT 4 /* Contains copy of task structure */
#define NT_PLATFORM 5 /* String from sysinfo(SI_PLATFORM) */
#define NT_AUXV 6 /* Contains copy of auxv array */
#define NT_GWINDOWS 7 /* Contains copy of gwindows struct */
#define NT_ASRS 8 /* Contains copy of asrset struct */
#define NT_PSTATUS 10 /* Contains copy of pstatus struct */
#define NT_PSINFO 13 /* Contains copy of psinfo struct */
#define NT_PRCRED 14 /* Contains copy of prcred struct */
#define NT_UTSNAME 15 /* Contains copy of utsname struct */
#define NT_LWPSTATUS 16 /* Contains copy of lwpstatus struct */
#define NT_LWPSINFO 17 /* Contains copy of lwpinfo struct */
#define NT_PRFPXREG 20 /* Contains copy of fprxregset struct */
#define NT_SIGINFO 0x53494749
/* Contains copy of siginfo_t,
* size might increase
*/
#define NT_FILE 0x46494c45
/* Contains information about mapped
* files
*/
#define NT_PRXFPREG 0x46e62b7f
/* Contains copy of user_fxsr_struct */
#define NT_PPC_VMX 0x100 /* PowerPC Altivec/VMX registers */
#define NT_PPC_SPE 0x101 /* PowerPC SPE/EVR registers */
#define NT_PPC_VSX 0x102 /* PowerPC VSX registers */
#define NT_PPC_TAR 0x103 /* Target Address Register */
#define NT_PPC_PPR 0x104 /* Program Priority Register */
#define NT_PPC_DSCR 0x105 /* Data Stream Control Register */
#define NT_PPC_EBB 0x106 /* Event Based Branch Registers */
#define NT_PPC_PMU 0x107 /* Performance Monitor Registers */
#define NT_PPC_TM_CGPR 0x108 /* TM checkpointed GPR Registers */
#define NT_PPC_TM_CFPR 0x109 /* TM checkpointed FPR Registers */
#define NT_PPC_TM_CVMX 0x10a /* TM checkpointed VMX Registers */
#define NT_PPC_TM_CVSX 0x10b /* TM checkpointed VSX Registers */
#define NT_PPC_TM_SPR 0x10c /* TM Special Purpose Registers */
#define NT_PPC_TM_CTAR 0x10d /* TM checkpointed Target Address
* Register
*/
#define NT_PPC_TM_CPPR 0x10e /* TM checkpointed Program Priority
* Register
*/
#define NT_PPC_TM_CDSCR 0x10f /* TM checkpointed Data Stream Control
* Register
*/
#define NT_PPC_PKEY 0x110 /* Memory Protection Keys
* registers.
*/
#define NT_386_TLS 0x200 /* i386 TLS slots (struct user_desc) */
#define NT_386_IOPERM 0x201 /* x86 io permission bitmap (1=deny) */
#define NT_X86_XSTATE 0x202 /* x86 extended state using xsave */
#define NT_S390_HIGH_GPRS 0x300 /* s390 upper register halves */
#define NT_S390_TIMER 0x301 /* s390 timer register */
#define NT_S390_TODCMP 0x302 /* s390 TOD clock comparator register */
#define NT_S390_TODPREG 0x303 /* s390 TOD programmable register */
#define NT_S390_CTRS 0x304 /* s390 control registers */
#define NT_S390_PREFIX 0x305 /* s390 prefix register */
#define NT_S390_LAST_BREAK 0x306 /* s390 breaking event address */
#define NT_S390_SYSTEM_CALL 0x307 /* s390 system call restart data */
#define NT_S390_TDB 0x308 /* s390 transaction diagnostic block */
#define NT_S390_VXRS_LOW 0x309 /* s390 vector registers 0-15
* upper half.
*/
#define NT_S390_VXRS_HIGH 0x30a /* s390 vector registers 16-31. */
#define NT_S390_GS_CB 0x30b /* s390 guarded storage registers. */
#define NT_S390_GS_BC 0x30c /* s390 guarded storage
* broadcast control block.
*/
#define NT_S390_RI_CB 0x30d /* s390 runtime instrumentation. */
#define NT_ARM_VFP 0x400 /* ARM VFP/NEON registers */
#define NT_ARM_TLS 0x401 /* ARM TLS register */
#define NT_ARM_HW_BREAK 0x402 /* ARM hardware breakpoint registers */
#define NT_ARM_HW_WATCH 0x403 /* ARM hardware watchpoint registers */
#define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */
#define NT_ARM_SVE 0x405 /* ARM Scalable Vector Extension
* registers
*/
#define NT_ARM_PAC_MASK 0x406 /* ARM pointer authentication
* code masks.
*/
#define NT_ARM_PACA_KEYS 0x407 /* ARM pointer authentication
* address keys.
*/
#define NT_ARM_PACG_KEYS 0x408 /* ARM pointer authentication
* generic key.
*/
#define NT_VMCOREDD 0x700 /* Vmcore Device Dump Note. */
#define NT_MIPS_DSP 0x800 /* MIPS DSP ASE registers. */
#define NT_MIPS_FP_MODE 0x801 /* MIPS floating-point mode. */
#define NT_MIPS_MSA 0x802 /* MIPS SIMD registers. */
/* Legal values for the note segment descriptor types for object files. */
#define NT_VERSION 1 /* Contains a version string. */
#ifdef CONFIG_ENDIAN_BIG
# define ELF_DATA ELFDATA2MSB
#else
# define ELF_DATA ELFDATA2LSB
#endif
#endif /* __INCLUDE_ELF_H */
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