Re: [PATCH bpf-next v3 3/5] error-injection: Separate error-injection from kprobe

Josef Bacik
2018-01-10T15:36:15Z

On Wed, Jan 10, 2018 at 07:18:05PM +0900, Masami Hiramatsu wrote:
> Since error-injection framework is not limited to be used
> by kprobes, nor bpf. Other kernel subsystems can use it
> freely for checking safeness of error-injection, e.g.
> livepatch, ftrace etc.
> So this separate error-injection framework from kprobes.
>
> Some differences has been made:
>
> - "kprobe" word is removed from any APIs/structures.
> - BPF_ALLOW_ERROR_INJECTION() is renamed to
> ALLOW_ERROR_INJECTION() since it is not limited for BPF too.
> - CONFIG_FUNCTION_ERROR_INJECTION is the config item of this
> feature. It is automatically enabled if the arch supports
> error injection feature for kprobe or ftrace etc.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
> Changes in v3:
> - Fix a build error for asmlinkage on i386 by including compiler.h
> - Fix "CONFIG_FUNCTION_ERROR_INJECT" typo.
> - Separate CONFIG_MODULES dependent code
> - Add CONFIG_KPROBES dependency for arch_deref_entry_point()
> - Call error-injection init function in late_initcall stage.
> - Fix read-side mutex lock
> - Some cosmetic cleanups
> ---
> arch/Kconfig | 2
> arch/x86/Kconfig | 2
> arch/x86/include/asm/error-injection.h | 13 ++
> arch/x86/kernel/kprobes/core.c | 14 --
> arch/x86/lib/Makefile | 1
> arch/x86/lib/error-inject.c | 19 +++
> fs/btrfs/disk-io.c | 2
> fs/btrfs/free-space-cache.c | 2
> include/asm-generic/error-injection.h | 20 +++
> include/asm-generic/vmlinux.lds.h | 14 +-
> include/linux/bpf.h | 12 --
> include/linux/error-injection.h | 21 +++
> include/linux/kprobes.h | 1
> include/linux/module.h | 6 -
> kernel/kprobes.c | 163 ------------------------
> kernel/module.c | 8 +
> kernel/trace/Kconfig | 2
> kernel/trace/bpf_trace.c | 2
> kernel/trace/trace_kprobe.c | 3
> lib/Kconfig.debug | 4 +
> lib/Makefile | 1
> lib/error-inject.c | 213 ++++++++++++++++++++++++++++++++
> 22 files changed, 315 insertions(+), 210 deletions(-)
> create mode 100644 arch/x86/include/asm/error-injection.h
> create mode 100644 arch/x86/lib/error-inject.c
> create mode 100644 include/asm-generic/error-injection.h
> create mode 100644 include/linux/error-injection.h
> create mode 100644 lib/error-inject.c
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index d3f4aaf9cb7a..97376accfb14 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -196,7 +196,7 @@ config HAVE_OPTPROBES
> config HAVE_KPROBES_ON_FTRACE
> bool
>
> -config HAVE_KPROBE_OVERRIDE
> +config HAVE_FUNCTION_ERROR_INJECTION
> bool
>
> config HAVE_NMI
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 45dc6233f2b9..366b19cb79b7 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -154,7 +154,7 @@ config X86
> select HAVE_KERNEL_XZ
> select HAVE_KPROBES
> select HAVE_KPROBES_ON_FTRACE
> - select HAVE_KPROBE_OVERRIDE
> + select HAVE_FUNCTION_ERROR_INJECTION
> select HAVE_KRETPROBES
> select HAVE_KVM
> select HAVE_LIVEPATCH if X86_64
> diff --git a/arch/x86/include/asm/error-injection.h b/arch/x86/include/asm/error-injection.h
> new file mode 100644
> index 000000000000..47b7a1296245
> --- /dev/null
> +++ b/arch/x86/include/asm/error-injection.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_ERROR_INJECTION_H
> +#define _ASM_ERROR_INJECTION_H
> +
> +#include <linux/compiler.h>
> +#include <linux/linkage.h>
> +#include <asm/ptrace.h>
> +#include <asm-generic/error-injection.h>
> +
> +asmlinkage void just_return_func(void);
> +void override_function_with_return(struct pt_regs *regs);
> +
> +#endif /* _ASM_ERROR_INJECTION_H */
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index b02a377d5905..bd36f3c33cd0 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -1183,17 +1183,3 @@ int arch_trampoline_kprobe(struct kprobe *p)
> {
> return 0;
> }
> -
> -asmlinkage void override_func(void);
> -asm(
> - ".type override_func, @function\n"
> - "override_func:\n"
> - " ret\n"
> - ".size override_func, .-override_func\n"
> -);
> -
> -void arch_kprobe_override_function(struct pt_regs *regs)
> -{
> - regs->ip = (unsigned long)&override_func;
> -}
> -NOKPROBE_SYMBOL(arch_kprobe_override_function);
> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> index 7b181b61170e..171377b83be1 100644
> --- a/arch/x86/lib/Makefile
> +++ b/arch/x86/lib/Makefile
> @@ -26,6 +26,7 @@ lib-y += memcpy_$(BITS).o
> lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
> lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-eval.o
> lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
> +lib-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
>
> obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
>
> diff --git a/arch/x86/lib/error-inject.c b/arch/x86/lib/error-inject.c
> new file mode 100644
> index 000000000000..7b881d03d0dd
> --- /dev/null
> +++ b/arch/x86/lib/error-inject.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/error-injection.h>
> +#include <linux/kprobes.h>
> +
> +asmlinkage void just_return_func(void);
> +
> +asm(
> + ".type just_return_func, @function\n"
> + "just_return_func:\n"
> + " ret\n"
> + ".size just_return_func, .-just_return_func\n"
> +);
> +
> +void override_function_with_return(struct pt_regs *regs)
> +{
> + regs->ip = (unsigned long)&just_return_func;
> +}
> +NOKPROBE_SYMBOL(override_function_with_return);
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 5da18ebc9222..5c540129ad81 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3124,7 +3124,7 @@ int open_ctree(struct super_block *sb,
> goto fail_block_groups;
> goto retry_root_backup;
> }
> -BPF_ALLOW_ERROR_INJECTION(open_ctree);
> +ALLOW_ERROR_INJECTION(open_ctree);
>
> static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
> {
> diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
> index fb1382893bfc..2a75e088b215 100644
> --- a/fs/btrfs/free-space-cache.c
> +++ b/fs/btrfs/free-space-cache.c
> @@ -333,7 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,
>
> return 0;
> }
> -BPF_ALLOW_ERROR_INJECTION(io_ctl_init);
> +ALLOW_ERROR_INJECTION(io_ctl_init);
>
> static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
> {
> diff --git a/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
> new file mode 100644
> index 000000000000..08352c9d9f97
> --- /dev/null
> +++ b/include/asm-generic/error-injection.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_GENERIC_ERROR_INJECTION_H
> +#define _ASM_GENERIC_ERROR_INJECTION_H
> +
> +#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
> +#ifdef CONFIG_FUNCTION_ERROR_INJECTION
> +/*
> + * Whitelist ganerating macro. Specify functions which can be
> + * error-injectable using this macro.
> + */
> +#define ALLOW_ERROR_INJECTION(fname) \
> +static unsigned long __used \
> + __attribute__((__section__("_error_injection_whitelist"))) \
> + _eil_addr_##fname = (unsigned long)fname;
> +#else
> +#define ALLOW_ERROR_INJECTION(fname)
> +#endif
> +#endif
> +
> +#endif /* _ASM_GENERIC_ERROR_INJECTION_H */
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index a2e8582d094a..f2068cca5206 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -136,13 +136,13 @@
> #define KPROBE_BLACKLIST()
> #endif
>
> -#ifdef CONFIG_BPF_KPROBE_OVERRIDE
> -#define ERROR_INJECT_LIST() . = ALIGN(8); \
> - VMLINUX_SYMBOL(__start_kprobe_error_inject_list) = .; \
> - KEEP(*(_kprobe_error_inject_list)) \
> - VMLINUX_SYMBOL(__stop_kprobe_error_inject_list) = .;
> +#ifdef CONFIG_FUNCTION_ERROR_INJECTION
> +#define ERROR_INJECT_WHITELIST() . = ALIGN(8); \
> + VMLINUX_SYMBOL(__start_error_injection_whitelist) = .;\
> + KEEP(*(_error_injection_whitelist)) \
> + VMLINUX_SYMBOL(__stop_error_injection_whitelist) = .;
> #else
> -#define ERROR_INJECT_LIST()
> +#define ERROR_INJECT_WHITELIST()
> #endif
>
> #ifdef CONFIG_EVENT_TRACING
> @@ -573,7 +573,7 @@
> FTRACE_EVENTS() \
> TRACE_SYSCALLS() \
> KPROBE_BLACKLIST() \
> - ERROR_INJECT_LIST() \
> + ERROR_INJECT_WHITELIST() \
> MEM_DISCARD(init.rodata) \
> CLK_OF_TABLES() \
> RESERVEDMEM_OF_TABLES() \
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 9e03046d1df2..ea865bb9f676 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -16,6 +16,7 @@
> #include <linux/rbtree_latch.h>
> #include <linux/numa.h>
> #include <linux/wait.h>
> +#include <linux/error-injection.h>
>

I assume you did this because we include linux/bpf.h for the
BPF_ALLOW_ERROR_INJECTION() stuff in btrfs. Can we just drop this include here,
and change the users of ALLOW_ERROR_INJECTION() to include error-injection.h
instead?

<snip>

> +/*
> + * error_injection/whitelist -- shows which functions can be overridden for
> + * error injection.
> + */
> +static void *ei_seq_start(struct seq_file *m, loff_t *pos)
> +{
> + mutex_lock(&ei_mutex);
> + return seq_list_start(&error_injection_list, *pos);
> +}
> +
> +static void ei_seq_stop(struct seq_file *m, void *v)
> +{
> + mutex_unlock(&ei_mutex);
> +}
> +
> +static void *ei_seq_next(struct seq_file *m, void *v, loff_t *pos)
> +{
> + return seq_list_next(v, &error_injection_list, pos);
> +}
> +
> +static int ei_seq_show(struct seq_file *m, void *v)
> +{
> + struct ei_entry *ent = list_entry(v, struct ei_entry, list);
> +
> + seq_printf(m, "%pf\n", (void *)ent->start_addr);

Can we bring back the sprint_symbol() thing I did originally here so it's nice
and easy to sanity check stuff is working? Thanks

Josef