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Message-Id: <cover.1435602481.git.luto@kernel.org> Date: Mon, 29 Jun 2015 12:33:32 -0700 From: Andy Lutomirski <luto@...nel.org> To: x86@...nel.org, linux-kernel@...r.kernel.org Cc: Frédéric Weisbecker <fweisbec@...il.com>, Rik van Riel <riel@...hat.com>, Oleg Nesterov <oleg@...hat.com>, Denys Vlasenko <vda.linux@...glemail.com>, Borislav Petkov <bp@...en8.de>, Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, paulmck@...ux.vnet.ibm.com, Andy Lutomirski <luto@...nel.org> Subject: [PATCH v4 00/17] x86: Rewrite exit-to-userspace code This is the first big batch of x86 asm-to-C conversion patches. The exit-to-usermode code is copied in several places and is written in a nasty combination of asm and C. It's not at all clear what it's supposed to do, and the way it's structured makes it very hard to work with. For example, it's not even clear why syscall exit hooks are called only once per syscall right now. (It seems to be a side effect of the way that rdi and rdx are handled in the asm loop, and it seems reliable, but it's still pointlessly complicated.) The existing code also makes context tracking overly complicated and hard to understand. Finally, it's nearly impossible for anyone to change what happens on exit to usermode, since the existing code is so fragile. I tried to clean it up incrementally, but I decided it was too hard. Instead, this series just replaces the code. It seems to work. Context tracking in particular works very differently now. The low-level entry code checks that we're in CONTEXT_USER and switches to CONTEXT_KERNEL. The exit code does the reverse. There is no need to track what CONTEXT_XYZ state we came from, because we already know. Similarly, SCHEDULE_USER is gone, since we can reschedule if needed by simply calling schedule() from C code. The main things that are missing are that I haven't done the 32-bit parts (anyone want to help?) and therefore I haven't deleted the old C code. I also think this may break UML for trivial reasons. IRQ context tracking is still messy. One the cleanup progresses to the point that we can enter CONTEXT_KERNEL in syscalls before enabling interrupts, we can fully clean up IRQ context tracking. Once these land, I'll send some more :) Note: we might want to backport patches 1 and 2. Changes from v3: - Add the syscall_arg_fault_32 test. - Fix a pre-existing bad syscall arg buglet. - Fix an asm glitch due to a bad rebase. - Fix a CONFIG_PROVE_LOCKDEP warning. Borislav: the end result of this series differs from the v3.91 that I only in the removal of a single trailing tab. The badarg patch is in a different place now, though, since we might want to backport it. Changes from v2: Misplaced the actual list -- sorry. Changes from v1: - Fix bisection failure by squashing the 64-bit native and compat syscall conversions together. The intermediate state didn't built, and fixing it isn't worthwhile (the results will be harder to understand). - Replace context_tracking_assert_state with CT_WARN_ON and ct_state. - The last two patches are now. I incorrectly thought that we weren't ready for them yet on 32-bit kernels, but I was wrong. Andy Lutomirski (16): selftests/x86: Add a test for 32-bit fast syscall arg faults x86/entry/64/compat: Fix bad fast syscall arg failure path context_tracking: Add ct_state and CT_WARN_ON notifiers: Assert that RCU is watching in notify_die x86: Move C entry and exit code to arch/x86/entry/common.c x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries x86/entry: Add enter_from_user_mode and use it in syscalls x86/entry: Add new, comprehensible entry and exit hooks x86/entry/64: Really create an error-entry-from-usermode code path x86/entry/64: Migrate 64-bit and compat syscalls to new exit hooks x86/asm/entry/64: Save all regs on interrupt entry x86/asm/entry/64: Simplify irq stack pt_regs handling x86/asm/entry/64: Migrate error and interrupt exit work to C x86/entry: Remove exception_enter from most trap handlers x86/entry: Remove SCHEDULE_USER and asm/context-tracking.h x86/irq: Document how IRQ context tracking works and add an assertion Ingo Molnar (1): uml: Fix do_signal() prototype arch/um/include/shared/kern_util.h | 3 +- arch/um/kernel/process.c | 6 +- arch/um/kernel/signal.c | 8 +- arch/um/kernel/tlb.c | 2 +- arch/um/kernel/trap.c | 2 +- arch/x86/entry/Makefile | 1 + arch/x86/entry/common.c | 374 ++++++++++++++++++++++++ arch/x86/entry/entry_64.S | 180 +++--------- arch/x86/entry/entry_64_compat.S | 47 ++- arch/x86/include/asm/context_tracking.h | 10 - arch/x86/include/asm/signal.h | 1 + arch/x86/include/asm/traps.h | 4 +- arch/x86/kernel/cpu/mcheck/mce.c | 5 +- arch/x86/kernel/cpu/mcheck/p5.c | 5 +- arch/x86/kernel/cpu/mcheck/winchip.c | 4 +- arch/x86/kernel/irq.c | 15 + arch/x86/kernel/ptrace.c | 202 +------------ arch/x86/kernel/signal.c | 28 +- arch/x86/kernel/traps.c | 87 ++---- include/linux/context_tracking.h | 15 + include/linux/context_tracking_state.h | 1 + kernel/notifier.c | 2 + tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/syscall_arg_fault.c | 130 ++++++++ 24 files changed, 672 insertions(+), 462 deletions(-) create mode 100644 arch/x86/entry/common.c delete mode 100644 arch/x86/include/asm/context_tracking.h create mode 100644 tools/testing/selftests/x86/syscall_arg_fault.c -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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