From 620b155034570f577470cf5309f741bac6a6e32b Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Wed, 6 May 2015 11:52:32 +0100 Subject: [PATCH] MIPS: fix FP mode selection in lieu of .MIPS.abiflags data Commit 46490b572544 ("MIPS: kernel: elf: Improve the overall ABI and FPU mode checks") reworked the ELF FP ABI mode selection logic, but when CONFIG_MIPS_O32_FP64_SUPPORT is enabled it breaks the use of binaries which have no PT_MIPS_ABIFLAGS program header & associated .MIPS.abiflags section. A default mode is selected based upon whether the ELF contains MIPS32 or MIPS64 code, but that selection is made in arch_elf_pt_proc. arch_elf_pt_proc only executes when a PT_MIPS_ABIFLAGS program header is found. If one is not found then arch_elf_pt_proc is never called, and no default overall_fp_mode value is selected. When arch_check_elf is called, both abi0 & abi1 are MIPS_ABI_FP_UNKNOWN which leads to both prog_req & interp_req being set to none_req. none_req matches none of the conditions for mode selection at the end of arch_check_elf, so overall_fp_mode is left untouched. Finally once mips_set_personality_fp is called the BUG() in the default case is then hit & the kernel likely panics. Fix this by moving the selection of a default overall mode to the start of arch_check_elf, which runs once per ELF executed regardless of whether it has a PT_MIPS_ABIFLAGS program header. Signed-off-by: Paul Burton Cc: Markos Chandras Cc: Matthew Fortune Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # v4.0+ Patchwork: http://patchwork.linux-mips.org/patch/9978/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/elf.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c index be4899f3c393..4a4d9e067c89 100644 --- a/arch/mips/kernel/elf.c +++ b/arch/mips/kernel/elf.c @@ -76,14 +76,6 @@ int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf, /* Lets see if this is an O32 ELF */ if (ehdr32->e_ident[EI_CLASS] == ELFCLASS32) { - /* FR = 1 for N32 */ - if (ehdr32->e_flags & EF_MIPS_ABI2) - state->overall_fp_mode = FP_FR1; - else - /* Set a good default FPU mode for O32 */ - state->overall_fp_mode = cpu_has_mips_r6 ? - FP_FRE : FP_FR0; - if (ehdr32->e_flags & EF_MIPS_FP64) { /* * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it @@ -104,9 +96,6 @@ int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf, (char *)&abiflags, sizeof(abiflags)); } else { - /* FR=1 is really the only option for 64-bit */ - state->overall_fp_mode = FP_FR1; - if (phdr64->p_type != PT_MIPS_ABIFLAGS) return 0; if (phdr64->p_filesz < sizeof(abiflags)) @@ -137,6 +126,7 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, struct elf32_hdr *ehdr = _ehdr; struct mode_req prog_req, interp_req; int fp_abi, interp_fp_abi, abi0, abi1, max_abi; + bool is_mips64; if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT)) return 0; @@ -152,10 +142,22 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, abi0 = abi1 = fp_abi; } - /* ABI limits. O32 = FP_64A, N32/N64 = FP_SOFT */ - max_abi = ((ehdr->e_ident[EI_CLASS] == ELFCLASS32) && - (!(ehdr->e_flags & EF_MIPS_ABI2))) ? - MIPS_ABI_FP_64A : MIPS_ABI_FP_SOFT; + is_mips64 = (ehdr->e_ident[EI_CLASS] == ELFCLASS64) || + (ehdr->e_flags & EF_MIPS_ABI2); + + if (is_mips64) { + /* 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; + } else { + /* 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; + } if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) || (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN)) -- 2.39.5