From dcd497f99a1ef29a7c5e76142965be77e9dacabd Mon Sep 17 00:00:00 2001 From: Jesper Juhl Date: Thu, 23 Jun 2005 00:09:07 -0700 Subject: [PATCH] streamline preempt_count type across archs The preempt_count member of struct thread_info is currently either defined as int, unsigned int or __s32 depending on arch. This patch makes the type of preempt_count an int on all archs. Having preempt_count be an unsigned type prevents the catching of preempt_count < 0 bugs, and using int on some archs and __s32 on others is not exactely "neat" - much nicer when it's just int all over. A previous version of this patch was already ACK'ed by Robert Love, and the only change in this version of the patch compared to the one he ACK'ed is that this one also makes sure the preempt_count member is consistently commented. Signed-off-by: Jesper Juhl Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/thread_info.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/asm-um') diff --git a/include/asm-um/thread_info.h b/include/asm-um/thread_info.h index 1feaaf148ef..97267f059ef 100644 --- a/include/asm-um/thread_info.h +++ b/include/asm-um/thread_info.h @@ -17,7 +17,7 @@ struct thread_info { struct exec_domain *exec_domain; /* execution domain */ unsigned long flags; /* low level flags */ __u32 cpu; /* current CPU */ - __s32 preempt_count; /* 0 => preemptable, + int preempt_count; /* 0 => preemptable, <0 => BUG */ mm_segment_t addr_limit; /* thread address space: 0-0xBFFFFFFF for user -- cgit From 84dd8d7e9c080b4db66b00b8bc36ccf09a90f824 Mon Sep 17 00:00:00 2001 From: Paolo 'Blaisorblade' Giarrusso Date: Sat, 25 Jun 2005 14:55:26 -0700 Subject: [PATCH] uml: add profile_pc for i386 Cope with a conditional i386 definition, which is wrong for UML. Before we just used that one, but it wasn't defined for CONFIG_SMP, so in that case we got link errors. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Cc: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/ptrace-i386.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/asm-um') diff --git a/include/asm-um/ptrace-i386.h b/include/asm-um/ptrace-i386.h index 04222f35c43..fe882b9d917 100644 --- a/include/asm-um/ptrace-i386.h +++ b/include/asm-um/ptrace-i386.h @@ -32,6 +32,10 @@ #define PT_REGS_SYSCALL_RET(r) PT_REGS_EAX(r) #define PT_FIX_EXEC_STACK(sp) do ; while(0) +/* Cope with a conditional i386 definition. */ +#undef profile_pc +#define profile_pc(regs) PT_REGS_IP(regs) + #define user_mode(r) UPT_IS_USER(&(r)->regs) #endif -- cgit From d67b569f5f620c0fb95d5212642746b7ba9d29e4 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Thu, 7 Jul 2005 17:56:49 -0700 Subject: [PATCH] uml: skas0 - separate kernel address space on stock hosts UML has had two modes of operation - an insecure, slow mode (tt mode) in which the kernel is mapped into every process address space which requires no host kernel modifications, and a secure, faster mode (skas mode) in which the UML kernel is in a separate host address space, which requires a patch to the host kernel. This patch implements something very close to skas mode for hosts which don't support skas - I'm calling this skas0. It provides the security of the skas host patch, and some of the performance gains. The two main things that are provided by the skas patch, /proc/mm and PTRACE_FAULTINFO, are implemented in a way that require no host patch. For the remote address space changing stuff (mmap, munmap, and mprotect), we set aside two pages in the process above its stack, one of which contains a little bit of code which can call mmap et al. To update the address space, the system call information (system call number and arguments) are written to the stub page above the code. The %esp is set to the beginning of the data, the %eip is set the the start of the stub, and it repeatedly pops the information into its registers and makes the system call until it sees a system call number of zero. This is to amortize the cost of the context switch across multiple address space updates. When the updates are done, it SIGSTOPs itself, and the kernel process continues what it was doing. For a PTRACE_FAULTINFO replacement, we set up a SIGSEGV handler in the child, and let it handle segfaults rather than nullifying them. The handler is in the same page as the mmap stub. The second page is used as the stack. The handler reads cr2 and err from the sigcontext, sticks them at the base of the stack in a faultinfo struct, and SIGSTOPs itself. The kernel then reads the faultinfo and handles the fault. A complication on x86_64 is that this involves resetting the registers to the segfault values when the process is inside the kill system call. This breaks on x86_64 because %rcx will contain %rip because you tell SYSRET where to return to by putting the value in %rcx. So, this corrupts $rcx on return from the segfault. To work around this, I added an arch_finish_segv, which on x86 does nothing, but which on x86_64 ptraces the child back through the sigreturn. This causes %rcx to be restored by sigreturn and avoids the corruption. Ultimately, I think I will replace this with the trick of having it send itself a blocked signal which will be unblocked by the sigreturn. This will allow it to be stopped just after the sigreturn, and PTRACE_SYSCALLed without all the back-and-forth of PTRACE_SYSCALLing it through sigreturn. This runs on a stock host, so theoretically (and hopefully), tt mode isn't needed any more. We need to make sure that this is better in every way than tt mode, though. I'm concerned about the speed of address space updates and page fault handling, since they involve extra round-trips to the child. We can amortize the round-trip cost for large address space updates by writing all of the operations to the data page and having the child execute them all at the same time. This will help fork and exec, but not page faults, since they involve only one page. I can't think of any way to help page faults, except to add something like PTRACE_FAULTINFO to the host. There is PTRACE_SIGINFO, but UML doesn't use siginfo for SIGSEGV (or anything else) because there isn't enough information in the siginfo struct to handle page faults (the faulting operation type is missing). Adding that would make PTRACE_SIGINFO a usable equivalent to PTRACE_FAULTINFO. As for the code itself: - The system call stub is in arch/um/kernel/sys-$(SUBARCH)/stub.S. It is put in its own section of the binary along with stub_segv_handler in arch/um/kernel/skas/process.c. This is manipulated with run_syscall_stub in arch/um/kernel/skas/mem_user.c. syscall_stub will execute any system call at all, but it's only used for mmap, munmap, and mprotect. - The x86_64 stub calls sigreturn by hand rather than allowing the normal sigreturn to happen, because the normal sigreturn is a SA_RESTORER in UML's address space provided by libc. Needless to say, this is not available in the child's address space. Also, it does a couple of odd pops before that which restore the stack to the state it was in at the time the signal handler was called. - There is a new field in the arch mmu_context, which is now a union. This is the pid to be manipulated rather than the /proc/mm file descriptor. Code which deals with this now checks proc_mm to see whether it should use the usual skas code or the new code. - userspace_tramp is now used to create a new host process for every UML process, rather than one per UML processor. It checks proc_mm and ptrace_faultinfo to decide whether to map in the pages above its stack. - start_userspace now makes CLONE_VM conditional on proc_mm since we need separate address spaces now. - switch_mm_skas now just sets userspace_pid[0] to the new pid rather than PTRACE_SWITCH_MM. There is an addition to userspace which updates its idea of the pid being manipulated each time around the loop. This is important on exec, when the pid will change underneath userspace(). - The stub page has a pte, but it can't be mapped in using tlb_flush because it is part of tlb_flush. This is why it's required for it to be mapped in by userspace_tramp. Other random things: - The stub section in uml.lds.S is page aligned. This page is written out to the backing vm file in setup_physmem because it is mapped from there into user processes. - There's some confusion with TASK_SIZE now that there are a couple of extra pages that the process can't use. TASK_SIZE is considered by the elf code to be the usable process memory, which is reasonable, so it is decreased by two pages. This confuses the definition of USER_PGDS_IN_LAST_PML4, making it too small because of the rounding down of the uneven division. So we round it to the nearest PGDIR_SIZE rather than the lower one. - I added a missing PT_SYSCALL_ARG6_OFFSET macro. - um_mmu.h was made into a userspace-usable file. - proc_mm and ptrace_faultinfo are globals which say whether the host supports these features. - There is a bad interaction between the mm.nr_ptes check at the end of exit_mmap, stack randomization, and skas0. exit_mmap will stop freeing pages at the PGDIR_SIZE boundary after the last vma. If the stack isn't on the last page table page, the last pte page won't be freed, as it should be since the stub ptes are there, and exit_mmap will BUG because there is an unfreed page. To get around this, TASK_SIZE is set to the next lowest PGDIR_SIZE boundary and mm->nr_ptes is decremented after the calls to init_stub_pte. This ensures that we know the process stack (and all other process mappings) will be below the top page table page, and thus we know that mm->nr_ptes will be one too many, and can be decremented. Things that need fixing: - We may need better assurrences that the stub code is PIC. - The stub pte is set up in init_new_context_skas. - alloc_pgdir is probably the right place. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/mmu_context.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/asm-um') diff --git a/include/asm-um/mmu_context.h b/include/asm-um/mmu_context.h index 89bff310b7a..7529c9c853d 100644 --- a/include/asm-um/mmu_context.h +++ b/include/asm-um/mmu_context.h @@ -7,7 +7,9 @@ #define __UM_MMU_CONTEXT_H #include "linux/sched.h" +#include "linux/config.h" #include "choose-mode.h" +#include "um_mmu.h" #define get_mmu_context(task) do ; while(0) #define activate_context(tsk) do ; while(0) @@ -18,8 +20,6 @@ static inline void activate_mm(struct mm_struct *old, struct mm_struct *new) { } -extern void switch_mm_skas(int mm_fd); - static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk) { @@ -30,7 +30,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, cpu_set(cpu, next->cpu_vm_mask); if(next != &init_mm) CHOOSE_MODE((void) 0, - switch_mm_skas(next->context.skas.mm_fd)); + switch_mm_skas(&next->context.skas.id)); } } -- cgit From c40504e87e28c52258458a53fefcd63f58e11a42 Mon Sep 17 00:00:00 2001 From: Benjamin LaHaise Date: Tue, 12 Jul 2005 13:58:22 -0700 Subject: [PATCH] uml: tlb flushing fix This patch fixes a fairly serious tlb flushing bug that makes aio use under uml very unreliable -- SEGVs, Oops and panic()s occur as a result of stale tlb entires being used by uml when aio switches mms due to the fact that uml does not implement the activate_mm() hook. This patch introduces a simple but correct approach (read: hammer) for implementing activate_mm() in uml by doing a force_flush_all() if the new mm is different from old. With this patch in place, uml is able to succeed at the aio test case that was randomly faulting for me before. Cc: Jeff Dike Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/mmu_context.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/asm-um') diff --git a/include/asm-um/mmu_context.h b/include/asm-um/mmu_context.h index 7529c9c853d..095bb627b96 100644 --- a/include/asm-um/mmu_context.h +++ b/include/asm-um/mmu_context.h @@ -16,8 +16,12 @@ #define deactivate_mm(tsk,mm) do { } while (0) +extern void force_flush_all(void); + static inline void activate_mm(struct mm_struct *old, struct mm_struct *new) { + if (old != new) + force_flush_all(); } static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, -- cgit From 2e5e55923e315e8198f46f24f7ca37e1fd9aa102 Mon Sep 17 00:00:00 2001 From: Paolo 'Blaisorblade' Giarrusso Date: Thu, 14 Jul 2005 00:33:37 -0700 Subject: [PATCH] uml: consolidate modify_ldt *) Reorganize the two cases of sys_modify_ldt to share all the reasonably common code. *) Avoid memory allocation when unneeded (i.e. when we are writing and the passed buffer size is known), thus not returning ENOMEM (which isn't allowed for this syscall, even if there is no strict "specification"). *) Add copy_{from,to}_user to modify_ldt for TT mode. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Cc: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/ldt.h | 5 +++++ 1 file changed, 5 insertions(+) create mode 100644 include/asm-um/ldt.h (limited to 'include/asm-um') diff --git a/include/asm-um/ldt.h b/include/asm-um/ldt.h new file mode 100644 index 00000000000..e908439d338 --- /dev/null +++ b/include/asm-um/ldt.h @@ -0,0 +1,5 @@ +#ifndef __UM_LDT_H +#define __UM_LDT_H + +#include "asm/arch/ldt.h" +#endif -- cgit From 7c9034735eccbf82608a4602c59aaf6053ea9416 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Tue, 26 Jul 2005 11:29:55 -0600 Subject: [PATCH] Add emergency_restart() When the kernel is working well and we want to restart cleanly kernel_restart is the function to use. But in many instances the kernel wants to reboot when thing are expected to be working very badly such as from panic or a software watchdog handler. This patch adds the function emergency_restart() so that callers can be clear what semantics they expect when calling restart. emergency_restart() is expected to be callable from interrupt context and possibly reliable in even more trying circumstances. This is an initial generic implementation for all architectures. Signed-off-by: Eric W. Biederman Signed-off-by: Linus Torvalds --- include/asm-um/emergency-restart.h | 6 ++++++ 1 file changed, 6 insertions(+) create mode 100644 include/asm-um/emergency-restart.h (limited to 'include/asm-um') diff --git a/include/asm-um/emergency-restart.h b/include/asm-um/emergency-restart.h new file mode 100644 index 00000000000..108d8c48e42 --- /dev/null +++ b/include/asm-um/emergency-restart.h @@ -0,0 +1,6 @@ +#ifndef _ASM_EMERGENCY_RESTART_H +#define _ASM_EMERGENCY_RESTART_H + +#include + +#endif /* _ASM_EMERGENCY_RESTART_H */ -- cgit From 6f313b12335abf010802751c45249e7a0007a232 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Thu, 28 Jul 2005 21:16:05 -0700 Subject: [PATCH] uml: vm86 compile fix We added an include of asm/vm86.h in include/asm-i386/ptrace.h. Since UML includes the underlying arch's ptrace.h, it needs an asm/vm86.h in order to build. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-um/vm86.h | 6 ++++++ 1 file changed, 6 insertions(+) create mode 100644 include/asm-um/vm86.h (limited to 'include/asm-um') diff --git a/include/asm-um/vm86.h b/include/asm-um/vm86.h new file mode 100644 index 00000000000..7801f82de1f --- /dev/null +++ b/include/asm-um/vm86.h @@ -0,0 +1,6 @@ +#ifndef __UM_VM86_H +#define __UM_VM86_H + +#include "asm/arch/vm86.h" + +#endif -- cgit