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 000000000..7aa2c2360
--- /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);