From 3316ec8ccd34e19690a12e65801d605d25155031 Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Sat, 3 Oct 2020 23:25:34 -0400 Subject: x86/elf: Use e_machine to check for x32/ia32 in setup_additional_pages() Since TIF_X32 is going away, avoid using it to find the ELF type when choosing which additional pages to set up. According to SysV AMD64 ABI Draft, an AMD64 ELF object using ILP32 must have ELFCLASS32 with (E_MACHINE == EM_X86_64), so use that ELF field to differentiate a x32 object from a IA32 object when executing setup_additional_pages() in compat mode. Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20201004032536.1229030-9-krisman@collabora.com --- arch/x86/entry/vdso/vma.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86/entry') diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 9185cb1d13b9..50e5d3a2e70a 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -413,10 +413,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) #ifdef CONFIG_COMPAT int compat_arch_setup_additional_pages(struct linux_binprm *bprm, - int uses_interp) + int uses_interp, bool x32) { #ifdef CONFIG_X86_X32_ABI - if (test_thread_flag(TIF_X32)) { + if (x32) { if (!vdso64_enabled) return 0; return map_vdso_randomized(&vdso_image_x32); -- cgit v1.2.3 From ff170cd0595398a7b66cb40f249eb2f10c29b66d Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Sat, 3 Oct 2020 23:25:35 -0400 Subject: x86/mm: Convert mmu context ia32_compat into a proper flags field The ia32_compat attribute is a weird thing. It mirrors TIF_IA32 and TIF_X32 and is used only in two very unrelated places: (1) to decide if the vsyscall page is accessible (2) for uprobes to find whether the patched instruction is 32 or 64 bit. In preparation to remove the TIF flags, a new mechanism is required for ia32_compat, but given its odd semantics, adding a real flags field which configures these specific behaviours is the best option. So, set_personality_x64() can ask for the vsyscall page, which is not available in x32/ia32 and set_personality_ia32() can configure the uprobe code as needed. uprobe cannot rely on other methods like user_64bit_mode() to decide how to patch, so it needs some specific flag like this. Signed-off-by: Gabriel Krisman Bertazi Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski Link: https://lore.kernel.org/r/20201004032536.1229030-10-krisman@collabora.com --- arch/x86/entry/vsyscall/vsyscall_64.c | 2 +- arch/x86/include/asm/mmu.h | 9 +++++++-- arch/x86/include/asm/mmu_context.h | 2 +- arch/x86/kernel/process_64.c | 17 +++++++++++------ 4 files changed, 20 insertions(+), 10 deletions(-) (limited to 'arch/x86/entry') diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c index 44c33103a955..1b40b9297083 100644 --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -316,7 +316,7 @@ static struct vm_area_struct gate_vma __ro_after_init = { struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { #ifdef CONFIG_COMPAT - if (!mm || mm->context.ia32_compat) + if (!mm || !(mm->context.flags & MM_CONTEXT_HAS_VSYSCALL)) return NULL; #endif if (vsyscall_mode == NONE) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 9257667d13c5..5d7494631ea9 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -6,6 +6,12 @@ #include #include #include +#include + +/* Uprobes on this MM assume 32-bit code */ +#define MM_CONTEXT_UPROBE_IA32 BIT(0) +/* vsyscall page is accessible on this MM */ +#define MM_CONTEXT_HAS_VSYSCALL BIT(1) /* * x86 has arch-specific MMU state beyond what lives in mm_struct. @@ -33,8 +39,7 @@ typedef struct { #endif #ifdef CONFIG_X86_64 - /* True if mm supports a task running in 32 bit compatibility mode. */ - unsigned short ia32_compat; + unsigned short flags; #endif struct mutex lock; diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index d98016b83755..054a79157323 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -177,7 +177,7 @@ static inline void arch_exit_mmap(struct mm_struct *mm) static inline bool is_64bit_mm(struct mm_struct *mm) { return !IS_ENABLED(CONFIG_IA32_EMULATION) || - !(mm->context.ia32_compat == TIF_IA32); + !(mm->context.flags & MM_CONTEXT_UPROBE_IA32); } #else static inline bool is_64bit_mm(struct mm_struct *mm) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 5fb4103101f5..d6efaf6623c9 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -646,10 +646,8 @@ void set_personality_64bit(void) /* Pretend that this comes from a 64bit execve */ task_pt_regs(current)->orig_ax = __NR_execve; current_thread_info()->status &= ~TS_COMPAT; - - /* Ensure the corresponding mm is not marked. */ if (current->mm) - current->mm->context.ia32_compat = 0; + current->mm->context.flags = MM_CONTEXT_HAS_VSYSCALL; /* TBD: overwrites user setup. Should have two bits. But 64bit processes have always behaved this way, @@ -664,7 +662,8 @@ static void __set_personality_x32(void) clear_thread_flag(TIF_IA32); set_thread_flag(TIF_X32); if (current->mm) - current->mm->context.ia32_compat = TIF_X32; + current->mm->context.flags = 0; + current->personality &= ~READ_IMPLIES_EXEC; /* * in_32bit_syscall() uses the presence of the x32 syscall bit @@ -684,8 +683,14 @@ static void __set_personality_ia32(void) #ifdef CONFIG_IA32_EMULATION set_thread_flag(TIF_IA32); clear_thread_flag(TIF_X32); - if (current->mm) - current->mm->context.ia32_compat = TIF_IA32; + if (current->mm) { + /* + * uprobes applied to this MM need to know this and + * cannot use user_64bit_mode() at that time. + */ + current->mm->context.flags = MM_CONTEXT_UPROBE_IA32; + } + current->personality |= force_personality32; /* Prepare the first "return" to user space */ task_pt_regs(current)->orig_ax = __NR_ia32_execve; -- cgit v1.2.3