[PATCH 1/2] arm64: stacktrace: factor out kernel unwind state
Puranjay Mohan
puranjay12 at gmail.com
Tue Nov 28 00:52:14 PST 2023
Mark Rutland <mark.rutland at arm.com> writes:
> On arm64 we share some unwinding code between the regular kernel
> unwinder and the KVM hyp unwinder. Some of this common code only matters
> to the regular unwinder, e.g. the `kr_cur` and `task` fields in the
> common struct unwind_state.
>
> We're likely to add more state which only matters for regular kernel
> unwinding (or only for hyp unwinding). In preparation for such changes,
> this patch factors out the kernel-specific state into a new struct
> kunwind_state, and updates the kernel unwind code accordingly.
>
> There should be no functional change as a result of this patch.
>
Reviewed-by: Puranjay Mohan <puranjay12 at gmail.com>
Thanks,
Puranjay
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Kalesh Singh <kaleshsingh at google.com>
> Cc: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
> Cc: Mark Brown <broonie at kernel.org>
> Cc: Puranjay Mohan <puranjay12 at gmail.com>
> Cc: Will Deacon <will at kernel.org>
> ---
> arch/arm64/include/asm/stacktrace/common.h | 19 +---
> arch/arm64/include/asm/stacktrace/nvhe.h | 2 +-
> arch/arm64/kernel/stacktrace.c | 113 +++++++++++++--------
> 3 files changed, 74 insertions(+), 60 deletions(-)
>
> diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> index 508f734de46ee..f63dc654e545f 100644
> --- a/arch/arm64/include/asm/stacktrace/common.h
> +++ b/arch/arm64/include/asm/stacktrace/common.h
> @@ -9,7 +9,6 @@
> #ifndef __ASM_STACKTRACE_COMMON_H
> #define __ASM_STACKTRACE_COMMON_H
>
> -#include <linux/kprobes.h>
> #include <linux/types.h>
>
> struct stack_info {
> @@ -23,12 +22,6 @@ struct stack_info {
> * @fp: The fp value in the frame record (or the real fp)
> * @pc: The lr value in the frame record (or the real lr)
> *
> - * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
> - * associated with the most recently encountered replacement lr
> - * value.
> - *
> - * @task: The task being unwound.
> - *
> * @stack: The stack currently being unwound.
> * @stacks: An array of stacks which can be unwound.
> * @nr_stacks: The number of stacks in @stacks.
> @@ -36,10 +29,6 @@ struct stack_info {
> struct unwind_state {
> unsigned long fp;
> unsigned long pc;
> -#ifdef CONFIG_KRETPROBES
> - struct llist_node *kr_cur;
> -#endif
> - struct task_struct *task;
>
> struct stack_info stack;
> struct stack_info *stacks;
> @@ -66,14 +55,8 @@ static inline bool stackinfo_on_stack(const struct stack_info *info,
> return true;
> }
>
> -static inline void unwind_init_common(struct unwind_state *state,
> - struct task_struct *task)
> +static inline void unwind_init_common(struct unwind_state *state)
> {
> - state->task = task;
> -#ifdef CONFIG_KRETPROBES
> - state->kr_cur = NULL;
> -#endif
> -
> state->stack = stackinfo_get_unknown();
> }
>
> diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
> index 25ab83a315a76..44759281d0d43 100644
> --- a/arch/arm64/include/asm/stacktrace/nvhe.h
> +++ b/arch/arm64/include/asm/stacktrace/nvhe.h
> @@ -31,7 +31,7 @@ static inline void kvm_nvhe_unwind_init(struct unwind_state *state,
> unsigned long fp,
> unsigned long pc)
> {
> - unwind_init_common(state, NULL);
> + unwind_init_common(state);
>
> state->fp = fp;
> state->pc = pc;
> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
> index 17f66a74c745c..aafc89192787a 100644
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -8,6 +8,7 @@
> #include <linux/efi.h>
> #include <linux/export.h>
> #include <linux/ftrace.h>
> +#include <linux/kprobes.h>
> #include <linux/sched.h>
> #include <linux/sched/debug.h>
> #include <linux/sched/task_stack.h>
> @@ -18,6 +19,31 @@
> #include <asm/stack_pointer.h>
> #include <asm/stacktrace.h>
>
> +/*
> + * Kernel unwind state
> + *
> + * @common: Common unwind state.
> + * @task: The task being unwound.
> + * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
> + * associated with the most recently encountered replacement lr
> + * value.
> + */
> +struct kunwind_state {
> + struct unwind_state common;
> + struct task_struct *task;
> +#ifdef CONFIG_KRETPROBES
> + struct llist_node *kr_cur;
> +#endif
> +};
> +
> +static __always_inline void
> +kunwind_init(struct kunwind_state *state,
> + struct task_struct *task)
> +{
> + unwind_init_common(&state->common);
> + state->task = task;
> +}
> +
> /*
> * Start an unwind from a pt_regs.
> *
> @@ -26,13 +52,13 @@
> * The regs must be on a stack currently owned by the calling task.
> */
> static __always_inline void
> -unwind_init_from_regs(struct unwind_state *state,
> - struct pt_regs *regs)
> +kunwind_init_from_regs(struct kunwind_state *state,
> + struct pt_regs *regs)
> {
> - unwind_init_common(state, current);
> + kunwind_init(state, current);
>
> - state->fp = regs->regs[29];
> - state->pc = regs->pc;
> + state->common.fp = regs->regs[29];
> + state->common.pc = regs->pc;
> }
>
> /*
> @@ -44,12 +70,12 @@ unwind_init_from_regs(struct unwind_state *state,
> * The function which invokes this must be noinline.
> */
> static __always_inline void
> -unwind_init_from_caller(struct unwind_state *state)
> +kunwind_init_from_caller(struct kunwind_state *state)
> {
> - unwind_init_common(state, current);
> + kunwind_init(state, current);
>
> - state->fp = (unsigned long)__builtin_frame_address(1);
> - state->pc = (unsigned long)__builtin_return_address(0);
> + state->common.fp = (unsigned long)__builtin_frame_address(1);
> + state->common.pc = (unsigned long)__builtin_return_address(0);
> }
>
> /*
> @@ -63,35 +89,38 @@ unwind_init_from_caller(struct unwind_state *state)
> * call this for the current task.
> */
> static __always_inline void
> -unwind_init_from_task(struct unwind_state *state,
> - struct task_struct *task)
> +kunwind_init_from_task(struct kunwind_state *state,
> + struct task_struct *task)
> {
> - unwind_init_common(state, task);
> + kunwind_init(state, task);
>
> - state->fp = thread_saved_fp(task);
> - state->pc = thread_saved_pc(task);
> + state->common.fp = thread_saved_fp(task);
> + state->common.pc = thread_saved_pc(task);
> }
>
> static __always_inline int
> -unwind_recover_return_address(struct unwind_state *state)
> +kunwind_recover_return_address(struct kunwind_state *state)
> {
> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> if (state->task->ret_stack &&
> - (state->pc == (unsigned long)return_to_handler)) {
> + (state->common.pc == (unsigned long)return_to_handler)) {
> unsigned long orig_pc;
> - orig_pc = ftrace_graph_ret_addr(state->task, NULL, state->pc,
> - (void *)state->fp);
> - if (WARN_ON_ONCE(state->pc == orig_pc))
> + orig_pc = ftrace_graph_ret_addr(state->task, NULL,
> + state->common.pc,
> + (void *)state->common.fp);
> + if (WARN_ON_ONCE(state->common.pc == orig_pc))
> return -EINVAL;
> - state->pc = orig_pc;
> + state->common.pc = orig_pc;
> }
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> #ifdef CONFIG_KRETPROBES
> - if (is_kretprobe_trampoline(state->pc)) {
> - state->pc = kretprobe_find_ret_addr(state->task,
> - (void *)state->fp,
> - &state->kr_cur);
> + if (is_kretprobe_trampoline(state->common.pc)) {
> + unsigned long orig_pc;
> + orig_pc = kretprobe_find_ret_addr(state->task,
> + (void *)state->common.fp,
> + &state->kr_cur);
> + state->common.pc = orig_pc;
> }
> #endif /* CONFIG_KRETPROBES */
>
> @@ -106,38 +135,38 @@ unwind_recover_return_address(struct unwind_state *state)
> * and the location (but not the fp value) of B.
> */
> static __always_inline int
> -unwind_next(struct unwind_state *state)
> +kunwind_next(struct kunwind_state *state)
> {
> struct task_struct *tsk = state->task;
> - unsigned long fp = state->fp;
> + unsigned long fp = state->common.fp;
> int err;
>
> /* Final frame; nothing to unwind */
> if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
> return -ENOENT;
>
> - err = unwind_next_frame_record(state);
> + err = unwind_next_frame_record(&state->common);
> if (err)
> return err;
>
> - state->pc = ptrauth_strip_kernel_insn_pac(state->pc);
> + state->common.pc = ptrauth_strip_kernel_insn_pac(state->common.pc);
>
> - return unwind_recover_return_address(state);
> + return kunwind_recover_return_address(state);
> }
>
> static __always_inline void
> -unwind(struct unwind_state *state, stack_trace_consume_fn consume_entry,
> - void *cookie)
> +do_kunwind(struct kunwind_state *state, stack_trace_consume_fn consume_entry,
> + void *cookie)
> {
> - if (unwind_recover_return_address(state))
> + if (kunwind_recover_return_address(state))
> return;
>
> while (1) {
> int ret;
>
> - if (!consume_entry(cookie, state->pc))
> + if (!consume_entry(cookie, state->common.pc))
> break;
> - ret = unwind_next(state);
> + ret = kunwind_next(state);
> if (ret < 0)
> break;
> }
> @@ -190,22 +219,24 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
> STACKINFO_EFI,
> #endif
> };
> - struct unwind_state state = {
> - .stacks = stacks,
> - .nr_stacks = ARRAY_SIZE(stacks),
> + struct kunwind_state state = {
> + .common = {
> + .stacks = stacks,
> + .nr_stacks = ARRAY_SIZE(stacks),
> + },
> };
>
> if (regs) {
> if (task != current)
> return;
> - unwind_init_from_regs(&state, regs);
> + kunwind_init_from_regs(&state, regs);
> } else if (task == current) {
> - unwind_init_from_caller(&state);
> + kunwind_init_from_caller(&state);
> } else {
> - unwind_init_from_task(&state, task);
> + kunwind_init_from_task(&state, task);
> }
>
> - unwind(&state, consume_entry, cookie);
> + do_kunwind(&state, consume_entry, cookie);
> }
>
> static bool dump_backtrace_entry(void *arg, unsigned long where)
> --
> 2.30.2
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