// 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>
#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;
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);