From 42501254901627d3aa77c25165bbdc6d95ad05c2 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 9 Dec 2019 16:08:03 +0100 Subject: [PATCH] BACKPORT: bpf, x86, arm64: Enable jit by default when not built as always-on After Spectre 2 fix via 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") most major distros use BPF_JIT_ALWAYS_ON configuration these days which compiles out the BPF interpreter entirely and always enables the JIT. Also given recent fix in e1608f3fa857 ("bpf: Avoid setting bpf insns pages read-only when prog is jited"), we additionally avoid fragmenting the direct map for the BPF insns pages sitting in the general data heap since they are not used during execution. Latter is only needed when run through the interpreter. Since both x86 and arm64 JITs have seen a lot of exposure over the years, are generally most up to date and maintained, there is more downside in !BPF_JIT_ALWAYS_ON configurations to have the interpreter enabled by default rather than the JIT. Add a ARCH_WANT_DEFAULT_BPF_JIT config which archs can use to set the bpf_jit_{enable,kallsyms} to 1. Back in the days the bpf_jit_kallsyms knob was set to 0 by default since major distros still had /proc/kallsyms addresses exposed to unprivileged user space which is not the case anymore. Hence both knobs are set via BPF_JIT_DEFAULT_ON which is set to 'y' in case of BPF_JIT_ALWAYS_ON or ARCH_WANT_DEFAULT_BPF_JIT. Change-Id: I7720d3f7742125680bb43c15d35eda21483b804e Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Acked-by: Will Deacon Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/f78ad24795c2966efcc2ee19025fa3459f622185.1575903816.git.daniel@iogearbox.net --- arch/arm64/Kconfig | 1 + arch/x86/Kconfig | 1 + init/Kconfig | 7 +++++++ kernel/bpf/core.c | 4 ++-- 4 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 8dfff319617c..33a6f20e7f17 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -73,6 +73,7 @@ config ARM64 select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG select ARCH_SUPPORTS_NUMA_BALANCING select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT + select ARCH_WANT_DEFAULT_BPF_JIT select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select ARCH_WANT_FRAME_POINTERS select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 0d438140d592..725e93af8084 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -96,6 +96,7 @@ config X86 select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH + select ARCH_WANT_DEFAULT_BPF_JIT if X86_64 select ARCH_WANTS_DYNAMIC_TASK_STRUCT select ARCH_WANT_HUGE_PMD_SHARE if X86_64 select ARCH_WANTS_THP_SWAP if X86_64 diff --git a/init/Kconfig b/init/Kconfig index 78d3b49b0354..ce9ef0cd1b7e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1669,6 +1669,9 @@ config BPF_SYSCALL Enable the bpf() system call that allows to manipulate eBPF programs and maps via file descriptors. +config ARCH_WANT_DEFAULT_BPF_JIT + bool + config BPF_JIT_ALWAYS_ON bool "Permanently enable BPF JIT and remove BPF interpreter" depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT @@ -1686,6 +1689,10 @@ config BPF_UNPRIV_DEFAULT_OFF disable it by setting it to 1 (from which no other transition to 0 is possible anymore). +config BPF_JIT_DEFAULT_ON + def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON + depends on HAVE_EBPF_JIT && BPF_JIT + config USERFAULTFD bool "Enable userfaultfd() system call" depends on MMU diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index bb2a00379d88..88a7d28ca112 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -529,9 +529,9 @@ void bpf_prog_kallsyms_del_all(struct bpf_prog *fp) #ifdef CONFIG_BPF_JIT /* All BPF JIT sysctl knobs here. */ -int bpf_jit_enable __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_ALWAYS_ON); +int bpf_jit_enable __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON); +int bpf_jit_kallsyms __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON); int bpf_jit_harden __read_mostly; -int bpf_jit_kallsyms __read_mostly; long bpf_jit_limit __read_mostly; long bpf_jit_limit_max __read_mostly;