327 lines
10 KiB
C
327 lines
10 KiB
C
/* Machine-dependent program header inspection for the ELF loader.
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Copyright (C) 2014-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _DL_MACHINE_REJECT_PHDR_H
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#define _DL_MACHINE_REJECT_PHDR_H 1
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#include <unistd.h>
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#include <sys/prctl.h>
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#if defined PR_GET_FP_MODE && defined PR_SET_FP_MODE
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# define HAVE_PRCTL_FP_MODE 1
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#else
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# define HAVE_PRCTL_FP_MODE 0
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#endif
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/* Reject an object with a debug message. */
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#define REJECT(str, args...) \
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{ \
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if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS)) \
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_dl_debug_printf (str, ##args); \
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return true; \
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}
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/* Search the program headers for the ABI Flags. */
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static inline const ElfW(Phdr) *
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find_mips_abiflags (const ElfW(Phdr) *phdr, ElfW(Half) phnum)
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{
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const ElfW(Phdr) *ph;
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for (ph = phdr; ph < &phdr[phnum]; ++ph)
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if (ph->p_type == PT_MIPS_ABIFLAGS)
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return ph;
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return NULL;
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}
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/* Cache the FP ABI value from the PT_MIPS_ABIFLAGS program header. */
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static bool
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cached_fpabi_reject_phdr_p (struct link_map *l)
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{
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if (l->l_mach.fpabi == 0)
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{
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const ElfW(Phdr) *ph = find_mips_abiflags (l->l_phdr, l->l_phnum);
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if (ph)
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{
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Elf_MIPS_ABIFlags_v0 * mips_abiflags;
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if (ph->p_filesz < sizeof (Elf_MIPS_ABIFlags_v0))
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REJECT (" %s: malformed PT_MIPS_ABIFLAGS found\n", l->l_name);
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mips_abiflags = (Elf_MIPS_ABIFlags_v0 *) (l->l_addr + ph->p_vaddr);
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if (__glibc_unlikely (mips_abiflags->flags2 != 0))
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REJECT (" %s: unknown MIPS.abiflags flags2: %u\n", l->l_name,
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mips_abiflags->flags2);
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l->l_mach.fpabi = mips_abiflags->fp_abi;
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l->l_mach.odd_spreg = (mips_abiflags->flags1
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& MIPS_AFL_FLAGS1_ODDSPREG) != 0;
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}
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else
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{
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l->l_mach.fpabi = -1;
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l->l_mach.odd_spreg = true;
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}
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}
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return false;
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}
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/* Return a description of the specified floating-point ABI. */
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static const char *
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fpabi_string (int fpabi)
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{
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switch (fpabi)
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{
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case Val_GNU_MIPS_ABI_FP_ANY:
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return "Hard or soft float";
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case Val_GNU_MIPS_ABI_FP_DOUBLE:
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return "Hard float (double precision)";
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case Val_GNU_MIPS_ABI_FP_SINGLE:
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return "Hard float (single precision)";
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case Val_GNU_MIPS_ABI_FP_SOFT:
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return "Soft float";
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case Val_GNU_MIPS_ABI_FP_OLD_64:
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return "Unsupported FP64";
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case Val_GNU_MIPS_ABI_FP_XX:
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return "Hard float (32-bit CPU, Any FPU)";
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case Val_GNU_MIPS_ABI_FP_64:
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return "Hard float (32-bit CPU, 64-bit FPU)";
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case Val_GNU_MIPS_ABI_FP_64A:
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return "Hard float compat (32-bit CPU, 64-bit FPU)";
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case -1:
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return "Double precision, single precision or soft float";
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default:
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return "Unknown FP ABI";
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}
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}
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/* A structure to describe the requirements of each FP ABI extension.
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Each field says whether the ABI can be executed in that mode. The FR0 field
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is actually overloaded and means 'default' FR mode for the ABI. I.e. For
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O32 it is FR0 and for N32/N64 it is actually FR1. Since this logic is
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focussed on the intricacies of mode management for O32 we call the field
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FR0. */
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struct abi_req
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{
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bool single;
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bool soft;
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bool fr0;
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bool fr1;
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bool fre;
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};
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/* FP ABI requirements for all Val_GNU_MIPS_ABI_FP_* values. */
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static const struct abi_req reqs[Val_GNU_MIPS_ABI_FP_MAX + 1] =
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{{true, true, true, true, true}, /* Any */
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{false, false, true, false, true}, /* Double-float */
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{true, false, false, false, false}, /* Single-float */
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{false, true, false, false, false}, /* Soft-float */
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{false, false, false, false, false}, /* old-FP64 */
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{false, false, true, true, true}, /* FPXX */
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{false, false, false, true, false}, /* FP64 */
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{false, false, false, true, true}}; /* FP64A */
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/* FP ABI requirements for objects without a PT_MIPS_ABIFLAGS segment. */
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static const struct abi_req none_req = { true, true, true, false, true };
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/* Return true iff ELF program headers are incompatible with the running
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host. This verifies that floating-point ABIs are compatible and
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re-configures the hardware mode if necessary. This code handles both the
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DT_NEEDED libraries and the dlopen'ed libraries. It also accounts for the
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impact of dlclose. */
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static bool __attribute_used__
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elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
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const char *buf, size_t len, struct link_map *map,
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int fd)
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{
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const ElfW(Phdr) *ph = find_mips_abiflags (phdr, phnum);
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struct link_map *l;
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Lmid_t nsid;
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int in_abi = -1;
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struct abi_req in_req;
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Elf_MIPS_ABIFlags_v0 *mips_abiflags = NULL;
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bool perfect_match = false;
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#if _MIPS_SIM == _ABIO32
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unsigned int cur_mode = -1;
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# if HAVE_PRCTL_FP_MODE
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bool cannot_mode_switch = false;
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/* Get the current hardware mode. */
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cur_mode = __prctl (PR_GET_FP_MODE);
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# endif
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#endif
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/* Read the attributes section. */
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if (ph != NULL)
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{
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ElfW(Addr) size = ph->p_filesz;
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if (ph->p_offset + size <= len)
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mips_abiflags = (Elf_MIPS_ABIFlags_v0 *) (buf + ph->p_offset);
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else
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{
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mips_abiflags = alloca (size);
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__lseek (fd, ph->p_offset, SEEK_SET);
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if (__libc_read (fd, (void *) mips_abiflags, size) != size)
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REJECT (" unable to read PT_MIPS_ABIFLAGS\n");
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}
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if (size < sizeof (Elf_MIPS_ABIFlags_v0))
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REJECT (" contains malformed PT_MIPS_ABIFLAGS\n");
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if (__glibc_unlikely (mips_abiflags->flags2 != 0))
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REJECT (" unknown MIPS.abiflags flags2: %u\n", mips_abiflags->flags2);
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in_abi = mips_abiflags->fp_abi;
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}
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/* ANY is compatible with anything. */
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perfect_match |= (in_abi == Val_GNU_MIPS_ABI_FP_ANY);
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/* Unknown ABIs are rejected. */
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if (in_abi != -1 && in_abi > Val_GNU_MIPS_ABI_FP_MAX)
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REJECT (" uses unknown FP ABI: %u\n", in_abi);
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/* Obtain the initial requirements. */
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in_req = (in_abi == -1) ? none_req : reqs[in_abi];
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/* Check that the new requirement does not conflict with any currently
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loaded object. */
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for (nsid = 0; nsid < DL_NNS; ++nsid)
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for (l = GL(dl_ns)[nsid]._ns_loaded; l != NULL; l = l->l_next)
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{
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struct abi_req existing_req;
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if (cached_fpabi_reject_phdr_p (l))
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return true;
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#if _MIPS_SIM == _ABIO32
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/* A special case arises for O32 FP64 and FP64A where the kernel
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pre-dates PT_MIPS_ABIFLAGS. These ABIs will be blindly loaded even
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if the hardware mode is unavailable or disabled. In this
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circumstance the prctl call to obtain the current mode will fail.
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Detect this situation here and reject everything. This will
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effectively prevent dynamically linked applications from failing in
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unusual ways but there is nothing we can do to help static
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applications. */
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if ((l->l_mach.fpabi == Val_GNU_MIPS_ABI_FP_64A
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|| l->l_mach.fpabi == Val_GNU_MIPS_ABI_FP_64)
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&& cur_mode == -1)
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REJECT (" found %s running in the wrong mode\n",
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fpabi_string (l->l_mach.fpabi));
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#endif
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/* Found a perfect match, success. */
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perfect_match |= (in_abi == l->l_mach.fpabi);
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/* Unknown ABIs are rejected. */
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if (l->l_mach.fpabi != -1 && l->l_mach.fpabi > Val_GNU_MIPS_ABI_FP_MAX)
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REJECT (" found unknown FP ABI: %u\n", l->l_mach.fpabi);
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existing_req = (l->l_mach.fpabi == -1 ? none_req
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: reqs[l->l_mach.fpabi]);
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/* Merge requirements. */
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in_req.soft &= existing_req.soft;
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in_req.single &= existing_req.single;
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in_req.fr0 &= existing_req.fr0;
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in_req.fr1 &= existing_req.fr1;
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in_req.fre &= existing_req.fre;
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/* If there is at least one mode which is still usable then the new
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object can be loaded. */
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if (in_req.single || in_req.soft || in_req.fr1 || in_req.fr0
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|| in_req.fre)
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{
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#if _MIPS_SIM == _ABIO32 && HAVE_PRCTL_FP_MODE
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/* Account for loaded ABIs which prohibit mode switching. */
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if (l->l_mach.fpabi == Val_GNU_MIPS_ABI_FP_XX)
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cannot_mode_switch |= l->l_mach.odd_spreg;
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#endif
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}
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else
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REJECT (" uses %s, already loaded %s\n",
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fpabi_string (in_abi),
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fpabi_string (l->l_mach.fpabi));
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}
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#if _MIPS_SIM == _ABIO32
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/* At this point we know that the newly loaded object is compatible with all
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existing objects but the hardware mode may not be correct. */
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if ((in_req.fr1 || in_req.fre || in_req.fr0)
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&& !perfect_match)
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{
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if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS))
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_dl_debug_printf (" needs %s%s mode\n", in_req.fr0 ? "FR0 or " : "",
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(in_req.fre && !in_req.fr1) ? "FRE" : "FR1");
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/* If the PR_GET_FP_MODE is not supported then only FR0 is available.
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If the overall requirements cannot be met by FR0 then reject the
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object. */
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if (cur_mode == -1)
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return !in_req.fr0;
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# if HAVE_PRCTL_FP_MODE
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{
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unsigned int fr1_mode = PR_FP_MODE_FR;
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/* It is not possible to change the mode of a thread which may be
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executing FPXX code with odd-singles. If an FPXX object with
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odd-singles is loaded then just check the current mode is OK. This
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can be either the FR1 mode or FR0 if the requirements are met by
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FR0. */
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if (cannot_mode_switch)
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return (!(in_req.fre && cur_mode == (PR_FP_MODE_FR | PR_FP_MODE_FRE))
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&& !(in_req.fr1 && cur_mode == PR_FP_MODE_FR)
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&& !(in_req.fr0 && cur_mode == 0));
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/* If the overall requirements can be satisfied by FRE but not FR1 then
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fr1_mode must become FRE. */
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if (in_req.fre && !in_req.fr1)
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fr1_mode |= PR_FP_MODE_FRE;
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/* Set the new mode. Use fr1_mode if the requirements cannot be met by
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FR0. */
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if (!in_req.fr0)
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return __prctl (PR_SET_FP_MODE, fr1_mode) != 0;
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else if (__prctl (PR_SET_FP_MODE, /* fr0_mode */ 0) != 0)
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{
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/* Setting FR0 can validly fail on an R6 core so retry with the FR1
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mode as a fall back. */
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if (errno != ENOTSUP)
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return true;
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return __prctl (PR_SET_FP_MODE, fr1_mode) != 0;
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}
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}
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# endif /* HAVE_PRCTL_FP_MODE */
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}
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#endif /* _MIPS_SIM == _ABIO32 */
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return false;
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}
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#endif /* dl-machine-reject-phdr.h */
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