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Diffstat (limited to 'arch/mips/kernel/elf.c')
| -rw-r--r-- | arch/mips/kernel/elf.c | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c new file mode 100644 index 0000000000..7aa2c2360f --- /dev/null +++ b/arch/mips/kernel/elf.c @@ -0,0 +1,343 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2014 Imagination Technologies + * Author: Paul Burton <paul.burton@mips.com> + */ + +#include <linux/binfmts.h> +#include <linux/elf.h> +#include <linux/export.h> +#include <linux/sched.h> + +#include <asm/cpu-features.h> +#include <asm/cpu-info.h> +#include <asm/fpu.h> + +#ifdef CONFIG_MIPS_FP_SUPPORT + +/* Whether to accept legacy-NaN and 2008-NaN user binaries. */ +bool mips_use_nan_legacy; +bool mips_use_nan_2008; + +/* FPU modes */ +enum { + FP_FRE, + FP_FR0, + FP_FR1, +}; + +/** + * struct mode_req - ABI FPU mode requirements + * @single: The program being loaded needs an FPU but it will only issue + * single precision instructions meaning that it can execute in + * either FR0 or FR1. + * @soft: The soft(-float) requirement means that the program being + * loaded needs has no FPU dependency at all (i.e. it has no + * FPU instructions). + * @fr1: The program being loaded depends on FPU being in FR=1 mode. + * @frdefault: The program being loaded depends on the default FPU mode. + * That is FR0 for O32 and FR1 for N32/N64. + * @fre: The program being loaded depends on FPU with FRE=1. This mode is + * a bridge which uses FR=1 whilst still being able to maintain + * full compatibility with pre-existing code using the O32 FP32 + * ABI. + * + * More information about the FP ABIs can be found here: + * + * https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking#10.4.1._Basic_mode_set-up + * + */ + +struct mode_req { + bool single; + bool soft; + bool fr1; + bool frdefault; + bool fre; +}; + +static const struct mode_req fpu_reqs[] = { + [MIPS_ABI_FP_ANY] = { true, true, true, true, true }, + [MIPS_ABI_FP_DOUBLE] = { false, false, false, true, true }, + [MIPS_ABI_FP_SINGLE] = { true, false, false, false, false }, + [MIPS_ABI_FP_SOFT] = { false, true, false, false, false }, + [MIPS_ABI_FP_OLD_64] = { false, false, false, false, false }, + [MIPS_ABI_FP_XX] = { false, false, true, true, true }, + [MIPS_ABI_FP_64] = { false, false, true, false, false }, + [MIPS_ABI_FP_64A] = { false, false, true, false, true } +}; + +/* + * Mode requirements when .MIPS.abiflags is not present in the ELF. + * Not present means that everything is acceptable except FR1. + */ +static struct mode_req none_req = { true, true, false, true, true }; + +int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf, + bool is_interp, struct arch_elf_state *state) +{ + union { + struct elf32_hdr e32; + struct elf64_hdr e64; + } *ehdr = _ehdr; + struct elf32_phdr *phdr32 = _phdr; + struct elf64_phdr *phdr64 = _phdr; + struct mips_elf_abiflags_v0 abiflags; + bool elf32; + u32 flags; + int ret; + loff_t pos; + + elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32; + flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags; + + /* Let's see if this is an O32 ELF */ + if (elf32) { + if (flags & EF_MIPS_FP64) { + /* + * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it + * later if needed + */ + if (is_interp) + state->interp_fp_abi = MIPS_ABI_FP_OLD_64; + else + state->fp_abi = MIPS_ABI_FP_OLD_64; + } + if (phdr32->p_type != PT_MIPS_ABIFLAGS) + return 0; + + if (phdr32->p_filesz < sizeof(abiflags)) + return -EINVAL; + pos = phdr32->p_offset; + } else { + if (phdr64->p_type != PT_MIPS_ABIFLAGS) + return 0; + if (phdr64->p_filesz < sizeof(abiflags)) + return -EINVAL; + pos = phdr64->p_offset; + } + + ret = kernel_read(elf, &abiflags, sizeof(abiflags), &pos); + if (ret < 0) + return ret; + if (ret != sizeof(abiflags)) + return -EIO; + + /* Record the required FP ABIs for use by mips_check_elf */ + if (is_interp) + state->interp_fp_abi = abiflags.fp_abi; + else + state->fp_abi = abiflags.fp_abi; + + return 0; +} + +int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr, + struct arch_elf_state *state) +{ + union { + struct elf32_hdr e32; + struct elf64_hdr e64; + } *ehdr = _ehdr; + union { + struct elf32_hdr e32; + struct elf64_hdr e64; + } *iehdr = _interp_ehdr; + struct mode_req prog_req, interp_req; + int fp_abi, interp_fp_abi, abi0, abi1, max_abi; + bool elf32; + u32 flags; + + elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32; + flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags; + + /* + * Determine the NaN personality, reject the binary if not allowed. + * Also ensure that any interpreter matches the executable. + */ + if (flags & EF_MIPS_NAN2008) { + if (mips_use_nan_2008) + state->nan_2008 = 1; + else + return -ENOEXEC; + } else { + if (mips_use_nan_legacy) + state->nan_2008 = 0; + else + return -ENOEXEC; + } + if (has_interpreter) { + bool ielf32; + u32 iflags; + + ielf32 = iehdr->e32.e_ident[EI_CLASS] == ELFCLASS32; + iflags = ielf32 ? iehdr->e32.e_flags : iehdr->e64.e_flags; + + if ((flags ^ iflags) & EF_MIPS_NAN2008) + return -ELIBBAD; + } + + if (!IS_ENABLED(CONFIG_MIPS_O32_FP64_SUPPORT)) + return 0; + + fp_abi = state->fp_abi; + + if (has_interpreter) { + interp_fp_abi = state->interp_fp_abi; + + abi0 = min(fp_abi, interp_fp_abi); + abi1 = max(fp_abi, interp_fp_abi); + } else { + abi0 = abi1 = fp_abi; + } + + if (elf32 && !(flags & EF_MIPS_ABI2)) { + /* Default to a mode capable of running code expecting FR=0 */ + state->overall_fp_mode = cpu_has_mips_r6 ? FP_FRE : FP_FR0; + + /* Allow all ABIs we know about */ + max_abi = MIPS_ABI_FP_64A; + } else { + /* MIPS64 code always uses FR=1, thus the default is easy */ + state->overall_fp_mode = FP_FR1; + + /* Disallow access to the various FPXX & FP64 ABIs */ + max_abi = MIPS_ABI_FP_SOFT; + } + + if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) || + (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN)) + return -ELIBBAD; + + /* It's time to determine the FPU mode requirements */ + prog_req = (abi0 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi0]; + interp_req = (abi1 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi1]; + + /* + * Check whether the program's and interp's ABIs have a matching FPU + * mode requirement. + */ + prog_req.single = interp_req.single && prog_req.single; + prog_req.soft = interp_req.soft && prog_req.soft; + prog_req.fr1 = interp_req.fr1 && prog_req.fr1; + prog_req.frdefault = interp_req.frdefault && prog_req.frdefault; + prog_req.fre = interp_req.fre && prog_req.fre; + + /* + * Determine the desired FPU mode + * + * Decision making: + * + * - We want FR_FRE if FRE=1 and both FR=1 and FR=0 are false. This + * means that we have a combination of program and interpreter + * that inherently require the hybrid FP mode. + * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or + * fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU + * instructions so we don't care about the mode. We will simply use + * the one preferred by the hardware. In fpxx case, that ABI can + * handle both FR=1 and FR=0, so, again, we simply choose the one + * preferred by the hardware. Next, if we only use single-precision + * FPU instructions, and the default ABI FPU mode is not good + * (ie single + any ABI combination), we set again the FPU mode to the + * one is preferred by the hardware. Next, if we know that the code + * will only use single-precision instructions, shown by single being + * true but frdefault being false, then we again set the FPU mode to + * the one that is preferred by the hardware. + * - We want FP_FR1 if that's the only matching mode and the default one + * is not good. + * - Return with -ELIBADD if we can't find a matching FPU mode. + */ + if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1) + state->overall_fp_mode = FP_FRE; + else if ((prog_req.fr1 && prog_req.frdefault) || + (prog_req.single && !prog_req.frdefault)) + /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */ + state->overall_fp_mode = ((raw_current_cpu_data.fpu_id & MIPS_FPIR_F64) && + cpu_has_mips_r2_r6) ? + FP_FR1 : FP_FR0; + else if (prog_req.fr1) + state->overall_fp_mode = FP_FR1; + else if (!prog_req.fre && !prog_req.frdefault && + !prog_req.fr1 && !prog_req.single && !prog_req.soft) + return -ELIBBAD; + + return 0; +} + +static inline void set_thread_fp_mode(int hybrid, int regs32) +{ + if (hybrid) + set_thread_flag(TIF_HYBRID_FPREGS); + else + clear_thread_flag(TIF_HYBRID_FPREGS); + if (regs32) + set_thread_flag(TIF_32BIT_FPREGS); + else + clear_thread_flag(TIF_32BIT_FPREGS); +} + +void mips_set_personality_fp(struct arch_elf_state *state) +{ + /* + * This function is only ever called for O32 ELFs so we should + * not be worried about N32/N64 binaries. + */ + + if (!IS_ENABLED(CONFIG_MIPS_O32_FP64_SUPPORT)) + return; + + switch (state->overall_fp_mode) { + case FP_FRE: + set_thread_fp_mode(1, 0); + break; + case FP_FR0: + set_thread_fp_mode(0, 1); + break; + case FP_FR1: + set_thread_fp_mode(0, 0); + break; + default: + BUG(); + } +} + +/* + * Select the IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode + * in FCSR according to the ELF NaN personality. + */ +void mips_set_personality_nan(struct arch_elf_state *state) +{ + struct cpuinfo_mips *c = &boot_cpu_data; + struct task_struct *t = current; + + /* Do this early so t->thread.fpu.fcr31 won't be clobbered in case + * we are preempted before the lose_fpu(0) in start_thread. + */ + lose_fpu(0); + + t->thread.fpu.fcr31 = c->fpu_csr31; + switch (state->nan_2008) { + case 0: + break; + case 1: + if (!(c->fpu_msk31 & FPU_CSR_NAN2008)) + t->thread.fpu.fcr31 |= FPU_CSR_NAN2008; + if (!(c->fpu_msk31 & FPU_CSR_ABS2008)) + t->thread.fpu.fcr31 |= FPU_CSR_ABS2008; + break; + default: + BUG(); + } +} + +#endif /* CONFIG_MIPS_FP_SUPPORT */ + +int mips_elf_read_implies_exec(void *elf_ex, int exstack) +{ + /* + * Set READ_IMPLIES_EXEC only on non-NX systems that + * do not request a specific state via PT_GNU_STACK. + */ + return (!cpu_has_rixi && exstack == EXSTACK_DEFAULT); +} +EXPORT_SYMBOL(mips_elf_read_implies_exec); |