| Message ID | 20250320171559.3423224-2-song@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: livepatch: Enable livepatch without sframe | expand |
On Thu, Mar 20, 2025 at 10:16 AM Song Liu <song@kernel.org> wrote: > > static __always_inline void > @@ -230,8 +231,26 @@ kunwind_next_frame_record(struct kunwind_state *state) > new_fp = READ_ONCE(record->fp); > new_pc = READ_ONCE(record->lr); > > - if (!new_fp && !new_pc) > - return kunwind_next_frame_record_meta(state); > + if (!new_fp && !new_pc) { > + int ret; > + > + ret = kunwind_next_frame_record_meta(state); The exception case kunwind_next_regs_pc() will return 0 when unwind success. Should we return a different value for the success case of kunwind_next_regs_pc()? > + if (ret < 0) { > + /* > + * This covers two different conditions: > + * 1. ret == -ENOENT, unwinding is done. > + * 2. ret == -EINVAL, unwinding hit error. > + */ > + return ret; > + } > + /* > + * Searching across exception boundaries. The stack is now > + * unreliable. > + */ > + if (state->end_on_unreliable) > + return -EINVAL; > + return 0; > + }
On Thu, Mar 20, 2025 at 10:46 AM Weinan Liu <wnliu@google.com> wrote: > > On Thu, Mar 20, 2025 at 10:16 AM Song Liu <song@kernel.org> wrote: > > > > static __always_inline void > > @@ -230,8 +231,26 @@ kunwind_next_frame_record(struct kunwind_state *state) > > new_fp = READ_ONCE(record->fp); > > new_pc = READ_ONCE(record->lr); > > > > - if (!new_fp && !new_pc) > > - return kunwind_next_frame_record_meta(state); > > + if (!new_fp && !new_pc) { > > + int ret; > > + > > + ret = kunwind_next_frame_record_meta(state); > > The exception case kunwind_next_regs_pc() will return 0 when unwind success. > Should we return a different value for the success case of kunwind_next_regs_pc()? I am assuming once the unwinder hits an exception boundary, the stack is not 100% reliable. This does mean we will return -EINVAL for some reliable stack walk, but this is safer and good enough for livepatch. IIUC, SFrame based unwinder should not have this limitation. Thanks, Song > > > + if (ret < 0) { > > + /* > > + * This covers two different conditions: > > + * 1. ret == -ENOENT, unwinding is done. > > + * 2. ret == -EINVAL, unwinding hit error. > > + */ > > + return ret; > > + } > > + /* > > + * Searching across exception boundaries. The stack is now > > + * unreliable. > > + */ > > + if (state->end_on_unreliable) > > + return -EINVAL; > > + return 0; > > + } >
On Thu, Mar 20, 2025 at 10:15:58AM -0700, Song Liu wrote: > With proper exception boundary detection, it is possible to implment > arch_stack_walk_reliable without sframe. > > Note that, arch_stack_walk_reliable does not guarantee getting reliable > stack in all scenarios. Instead, it can reliably detect when the stack > trace is not reliable, which is enough to provide reliable livepatching. > > Signed-off-by: Song Liu <song@kernel.org> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
On Thu, 20 Mar 2025, Song Liu wrote: > With proper exception boundary detection, it is possible to implment > arch_stack_walk_reliable without sframe. > > Note that, arch_stack_walk_reliable does not guarantee getting reliable > stack in all scenarios. Instead, it can reliably detect when the stack > trace is not reliable, which is enough to provide reliable livepatching. > > Signed-off-by: Song Liu <song@kernel.org> Looks good to me. Reviewed-by: Miroslav Benes <mbenes@suse.cz> M
Hi song, On 10:15 Thu 20 Mar , Song Liu wrote: > With proper exception boundary detection, it is possible to implment > arch_stack_walk_reliable without sframe. > > Note that, arch_stack_walk_reliable does not guarantee getting reliable > stack in all scenarios. Instead, it can reliably detect when the stack > trace is not reliable, which is enough to provide reliable livepatching. > > Signed-off-by: Song Liu <song@kernel.org> > --- > arch/arm64/Kconfig | 2 +- > arch/arm64/kernel/stacktrace.c | 66 +++++++++++++++++++++++++--------- > 2 files changed, 51 insertions(+), 17 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 701d980ea921..31d5e1ee6089 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -276,6 +276,7 @@ config ARM64 > select HAVE_SOFTIRQ_ON_OWN_STACK > select USER_STACKTRACE_SUPPORT > select VDSO_GETRANDOM > + select HAVE_RELIABLE_STACKTRACE > help > ARM 64-bit (AArch64) Linux support. > > @@ -2500,4 +2501,3 @@ endmenu # "CPU Power Management" > source "drivers/acpi/Kconfig" > > source "arch/arm64/kvm/Kconfig" > - > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 1d9d51d7627f..7e07911d8694 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -56,6 +56,7 @@ struct kunwind_state { > enum kunwind_source source; > union unwind_flags flags; > struct pt_regs *regs; > + bool end_on_unreliable; > }; > > static __always_inline void > @@ -230,8 +231,26 @@ kunwind_next_frame_record(struct kunwind_state *state) > new_fp = READ_ONCE(record->fp); > new_pc = READ_ONCE(record->lr); > > - if (!new_fp && !new_pc) > - return kunwind_next_frame_record_meta(state); > + if (!new_fp && !new_pc) { > + int ret; > + > + ret = kunwind_next_frame_record_meta(state); > + if (ret < 0) { > + /* > + * This covers two different conditions: > + * 1. ret == -ENOENT, unwinding is done. > + * 2. ret == -EINVAL, unwinding hit error. > + */ > + return ret; > + } > + /* > + * Searching across exception boundaries. The stack is now > + * unreliable. > + */ > + if (state->end_on_unreliable) > + return -EINVAL; > + return 0; > + } > > unwind_consume_stack(&state->common, info, fp, sizeof(*record)); > > @@ -277,21 +296,24 @@ kunwind_next(struct kunwind_state *state) > > typedef bool (*kunwind_consume_fn)(const struct kunwind_state *state, void *cookie); > > -static __always_inline void > +static __always_inline int > do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state, > void *cookie) > { > - if (kunwind_recover_return_address(state)) > - return; > + int ret; > > - while (1) { > - int ret; > + ret = kunwind_recover_return_address(state); > + if (ret) > + return ret; > > + while (1) { > if (!consume_state(state, cookie)) > - break; > + return -EINVAL; > ret = kunwind_next(state); > + if (ret == -ENOENT) > + return 0; > if (ret < 0) > - break; > + return ret; > } > } > > @@ -324,10 +346,10 @@ do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state, > : stackinfo_get_unknown(); \ > }) > > -static __always_inline void > +static __always_inline int > kunwind_stack_walk(kunwind_consume_fn consume_state, > void *cookie, struct task_struct *task, > - struct pt_regs *regs) > + struct pt_regs *regs, bool end_on_unreliable) > { > struct stack_info stacks[] = { > stackinfo_get_task(task), > @@ -348,11 +370,12 @@ kunwind_stack_walk(kunwind_consume_fn consume_state, > .stacks = stacks, > .nr_stacks = ARRAY_SIZE(stacks), > }, > + .end_on_unreliable = end_on_unreliable, > }; > > if (regs) { > if (task != current) > - return; > + return -EINVAL; > kunwind_init_from_regs(&state, regs); > } else if (task == current) { > kunwind_init_from_caller(&state); > @@ -360,7 +383,7 @@ kunwind_stack_walk(kunwind_consume_fn consume_state, > kunwind_init_from_task(&state, task); > } > > - do_kunwind(&state, consume_state, cookie); > + return do_kunwind(&state, consume_state, cookie); > } > > struct kunwind_consume_entry_data { > @@ -384,7 +407,18 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, > .cookie = cookie, > }; > > - kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs); > + kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs, false); > +} > + > +noinline noinstr int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, > + void *cookie, struct task_struct *task) > +{ > + struct kunwind_consume_entry_data data = { > + .consume_entry = consume_entry, > + .cookie = cookie, > + }; > + > + return kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, NULL, true); > } > > struct bpf_unwind_consume_entry_data { > @@ -409,7 +443,7 @@ noinline noinstr void arch_bpf_stack_walk(bool (*consume_entry)(void *cookie, u6 > .cookie = cookie, > }; > > - kunwind_stack_walk(arch_bpf_unwind_consume_entry, &data, current, NULL); > + kunwind_stack_walk(arch_bpf_unwind_consume_entry, &data, current, NULL, false); > } > > static const char *state_source_string(const struct kunwind_state *state) > @@ -456,7 +490,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, > return; > > printk("%sCall trace:\n", loglvl); > - kunwind_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs); > + kunwind_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs, false); > > put_task_stack(tsk); > } > -- > 2.47.1 > Tested-by: Andrea della Porta <andrea.porta@suse.com> Thanks, Andrea
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 701d980ea921..31d5e1ee6089 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -276,6 +276,7 @@ config ARM64 select HAVE_SOFTIRQ_ON_OWN_STACK select USER_STACKTRACE_SUPPORT select VDSO_GETRANDOM + select HAVE_RELIABLE_STACKTRACE help ARM 64-bit (AArch64) Linux support. @@ -2500,4 +2501,3 @@ endmenu # "CPU Power Management" source "drivers/acpi/Kconfig" source "arch/arm64/kvm/Kconfig" - diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 1d9d51d7627f..7e07911d8694 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -56,6 +56,7 @@ struct kunwind_state { enum kunwind_source source; union unwind_flags flags; struct pt_regs *regs; + bool end_on_unreliable; }; static __always_inline void @@ -230,8 +231,26 @@ kunwind_next_frame_record(struct kunwind_state *state) new_fp = READ_ONCE(record->fp); new_pc = READ_ONCE(record->lr); - if (!new_fp && !new_pc) - return kunwind_next_frame_record_meta(state); + if (!new_fp && !new_pc) { + int ret; + + ret = kunwind_next_frame_record_meta(state); + if (ret < 0) { + /* + * This covers two different conditions: + * 1. ret == -ENOENT, unwinding is done. + * 2. ret == -EINVAL, unwinding hit error. + */ + return ret; + } + /* + * Searching across exception boundaries. The stack is now + * unreliable. + */ + if (state->end_on_unreliable) + return -EINVAL; + return 0; + } unwind_consume_stack(&state->common, info, fp, sizeof(*record)); @@ -277,21 +296,24 @@ kunwind_next(struct kunwind_state *state) typedef bool (*kunwind_consume_fn)(const struct kunwind_state *state, void *cookie); -static __always_inline void +static __always_inline int do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state, void *cookie) { - if (kunwind_recover_return_address(state)) - return; + int ret; - while (1) { - int ret; + ret = kunwind_recover_return_address(state); + if (ret) + return ret; + while (1) { if (!consume_state(state, cookie)) - break; + return -EINVAL; ret = kunwind_next(state); + if (ret == -ENOENT) + return 0; if (ret < 0) - break; + return ret; } } @@ -324,10 +346,10 @@ do_kunwind(struct kunwind_state *state, kunwind_consume_fn consume_state, : stackinfo_get_unknown(); \ }) -static __always_inline void +static __always_inline int kunwind_stack_walk(kunwind_consume_fn consume_state, void *cookie, struct task_struct *task, - struct pt_regs *regs) + struct pt_regs *regs, bool end_on_unreliable) { struct stack_info stacks[] = { stackinfo_get_task(task), @@ -348,11 +370,12 @@ kunwind_stack_walk(kunwind_consume_fn consume_state, .stacks = stacks, .nr_stacks = ARRAY_SIZE(stacks), }, + .end_on_unreliable = end_on_unreliable, }; if (regs) { if (task != current) - return; + return -EINVAL; kunwind_init_from_regs(&state, regs); } else if (task == current) { kunwind_init_from_caller(&state); @@ -360,7 +383,7 @@ kunwind_stack_walk(kunwind_consume_fn consume_state, kunwind_init_from_task(&state, task); } - do_kunwind(&state, consume_state, cookie); + return do_kunwind(&state, consume_state, cookie); } struct kunwind_consume_entry_data { @@ -384,7 +407,18 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, .cookie = cookie, }; - kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs); + kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs, false); +} + +noinline noinstr int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, + void *cookie, struct task_struct *task) +{ + struct kunwind_consume_entry_data data = { + .consume_entry = consume_entry, + .cookie = cookie, + }; + + return kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, NULL, true); } struct bpf_unwind_consume_entry_data { @@ -409,7 +443,7 @@ noinline noinstr void arch_bpf_stack_walk(bool (*consume_entry)(void *cookie, u6 .cookie = cookie, }; - kunwind_stack_walk(arch_bpf_unwind_consume_entry, &data, current, NULL); + kunwind_stack_walk(arch_bpf_unwind_consume_entry, &data, current, NULL, false); } static const char *state_source_string(const struct kunwind_state *state) @@ -456,7 +490,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, return; printk("%sCall trace:\n", loglvl); - kunwind_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs); + kunwind_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs, false); put_task_stack(tsk); }
With proper exception boundary detection, it is possible to implment arch_stack_walk_reliable without sframe. Note that, arch_stack_walk_reliable does not guarantee getting reliable stack in all scenarios. Instead, it can reliably detect when the stack trace is not reliable, which is enough to provide reliable livepatching. Signed-off-by: Song Liu <song@kernel.org> --- arch/arm64/Kconfig | 2 +- arch/arm64/kernel/stacktrace.c | 66 +++++++++++++++++++++++++--------- 2 files changed, 51 insertions(+), 17 deletions(-)