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arm64: stacktrace: factor out kernel unwind state
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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.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Puranjay Mohan <puranjay12@gmail.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20231124110511.2795958-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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Mark Rutland authored and willdeacon committed Dec 11, 2023
1 parent 2cc14f5 commit 1beef60
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Showing 3 changed files with 74 additions and 60 deletions.
19 changes: 1 addition & 18 deletions arch/arm64/include/asm/stacktrace/common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand All @@ -23,23 +22,13 @@ 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.
*/
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;
Expand All @@ -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();
}

Expand Down
2 changes: 1 addition & 1 deletion arch/arm64/include/asm/stacktrace/nvhe.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
113 changes: 72 additions & 41 deletions arch/arm64/kernel/stacktrace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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.
*
Expand All @@ -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;
}

/*
Expand All @@ -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);
}

/*
Expand All @@ -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 */

Expand All @@ -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;
}
Expand Down Expand Up @@ -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)
Expand Down

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