From: Weinan Liu <[email protected]> Add unwind_next_frame_sframe() function to unwind by sframe info. Built with GNU Binutils 2.42 to verify that this sframe unwinder can backtrace correctly on arm64.
To support livepatch, we need to add arch_stack_walk_reliable to support reliable stacktrace according to https://docs.kernel.org/livepatch/reliable-stacktrace.html#requirements report stacktrace is not reliable if we are not able to unwind the stack by sframe unwinder and fallback to FP based unwinder Signed-off-by: Weinan Liu <[email protected]> Signed-off-by: Dylan Hatch <[email protected]> Reviewed-by: Prasanna Kumar T S M <[email protected]> --- arch/arm64/include/asm/stacktrace/common.h | 6 ++ arch/arm64/kernel/setup.c | 2 + arch/arm64/kernel/stacktrace.c | 102 +++++++++++++++++++++ 3 files changed, 110 insertions(+) diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h index 821a8fdd31af..26449cd402db 100644 --- a/arch/arm64/include/asm/stacktrace/common.h +++ b/arch/arm64/include/asm/stacktrace/common.h @@ -25,6 +25,8 @@ struct stack_info { * @stack: The stack currently being unwound. * @stacks: An array of stacks which can be unwound. * @nr_stacks: The number of stacks in @stacks. + * @cfa: The sp value at the call site of the current function. + * @unreliable: Stacktrace is unreliable. */ struct unwind_state { unsigned long fp; @@ -33,6 +35,10 @@ struct unwind_state { struct stack_info stack; struct stack_info *stacks; int nr_stacks; +#ifdef CONFIG_SFRAME_UNWINDER + unsigned long cfa; + bool unreliable; +#endif }; static inline struct stack_info stackinfo_get_unknown(void) diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 77c7926a4df6..ac1da45da532 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -32,6 +32,7 @@ #include <linux/sched/task.h> #include <linux/scs.h> #include <linux/mm.h> +#include <linux/sframe_lookup.h> #include <asm/acpi.h> #include <asm/fixmap.h> @@ -375,6 +376,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p) "This indicates a broken bootloader or old kernel\n", boot_args[1], boot_args[2], boot_args[3]); } + init_sframe_table(); } static inline bool cpu_can_disable(unsigned int cpu) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 3ebcf8c53fb0..72e78024d05e 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -14,6 +14,7 @@ #include <linux/sched/debug.h> #include <linux/sched/task_stack.h> #include <linux/stacktrace.h> +#include <linux/sframe_lookup.h> #include <asm/efi.h> #include <asm/irq.h> @@ -244,6 +245,53 @@ kunwind_next_frame_record(struct kunwind_state *state) return 0; } +#ifdef CONFIG_SFRAME_UNWINDER +/* + * Unwind to the next frame according to sframe. + */ +static __always_inline int +unwind_next_frame_sframe(struct unwind_state *state) +{ + unsigned long fp = state->fp, ip = state->pc; + unsigned long base_reg, cfa; + unsigned long pc_addr, fp_addr; + struct sframe_ip_entry entry; + struct stack_info *info; + struct frame_record *record = (struct frame_record *)fp; + + int err; + + /* frame record alignment 8 bytes */ + if (fp & 0x7) + return -EINVAL; + + info = unwind_find_stack(state, fp, sizeof(*record)); + if (!info) + return -EINVAL; + + err = sframe_find_pc(ip, &entry); + if (err) + return -EINVAL; + + unwind_consume_stack(state, info, fp, sizeof(*record)); + + base_reg = entry.use_fp ? fp : state->cfa; + + /* Set up the initial CFA using fp based info if CFA is not set */ + if (!state->cfa) + cfa = fp - entry.fp_offset; + else + cfa = base_reg + entry.cfa_offset; + fp_addr = cfa + entry.fp_offset; + pc_addr = cfa + entry.ra_offset; + state->cfa = cfa; + state->fp = READ_ONCE(*(unsigned long *)(fp_addr)); + state->pc = READ_ONCE(*(unsigned long *)(pc_addr)); + + return 0; +} +#endif + /* * Unwind from one frame record (A) to the next frame record (B). * @@ -263,7 +311,20 @@ kunwind_next(struct kunwind_state *state) case KUNWIND_SOURCE_CALLER: case KUNWIND_SOURCE_TASK: case KUNWIND_SOURCE_REGS_PC: +#ifdef CONFIG_SFRAME_UNWINDER + if (!state->common.unreliable) + err = unwind_next_frame_sframe(&state->common); + + /* Fallback to FP based unwinder */ + if (err || state->common.unreliable) { err = kunwind_next_frame_record(state); + /* Mark its stacktrace result as unreliable if it is unwindable via FP */ + if (!err) + state->common.unreliable = true; + } +#else + err = kunwind_next_frame_record(state); +#endif break; default: err = -EINVAL; @@ -350,6 +411,9 @@ kunwind_stack_walk(kunwind_consume_fn consume_state, .common = { .stacks = stacks, .nr_stacks = ARRAY_SIZE(stacks), +#ifdef CONFIG_SFRAME_UNWINDER + .cfa = 0, +#endif }, }; @@ -390,6 +454,43 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs); } +#ifdef CONFIG_SFRAME_UNWINDER +struct kunwind_reliable_consume_entry_data { + stack_trace_consume_fn consume_entry; + void *cookie; + bool unreliable; +}; + +static __always_inline bool +arch_kunwind_reliable_consume_entry(const struct kunwind_state *state, void *cookie) +{ + struct kunwind_reliable_consume_entry_data *data = cookie; + + if (state->common.unreliable) { + data->unreliable = true; + return false; + } + return data->consume_entry(data->cookie, state->common.pc); +} + +noinline notrace int arch_stack_walk_reliable( + stack_trace_consume_fn consume_entry, + void *cookie, struct task_struct *task) +{ + struct kunwind_reliable_consume_entry_data data = { + .consume_entry = consume_entry, + .cookie = cookie, + .unreliable = false, + }; + + kunwind_stack_walk(arch_kunwind_reliable_consume_entry, &data, task, NULL); + + if (data.unreliable) + return -EINVAL; + + return 0; +} +#else static __always_inline bool arch_reliable_kunwind_consume_entry(const struct kunwind_state *state, void *cookie) { @@ -419,6 +520,7 @@ noinline noinstr int arch_stack_walk_reliable(stack_trace_consume_fn consume_ent return kunwind_stack_walk(arch_reliable_kunwind_consume_entry, &data, task, NULL); } +#endif struct bpf_unwind_consume_entry_data { bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp); -- 2.51.0.355.g5224444f11-goog
