[PATCH 1/8] perf arm64: Send pointer auth masks to ring buffer
Arnaldo Carvalho de Melo
acme at kernel.org
Wed Aug 10 06:23:04 PDT 2022
Em Mon, Jul 04, 2022 at 03:53:25PM +0100, Andrew Kilroy escreveu:
> Perf report cannot produce callgraphs using dwarf on arm64 where pointer
> authentication is enabled. This is because libunwind and libdw cannot
> unmangle instruction pointers that have a pointer authentication code
> (PAC) embedded in them.
>
> libunwind and libdw need to be given an instruction mask which they can
> use to arrive at the correct return address that does not contain the
> PAC.
>
> The bits in the return address that contain the PAC can differ by
> process, so this patch adds a new sample field PERF_SAMPLE_ARCH_1
> to allow the kernel to send the masks up to userspace perf.
>
> This field can be used in a architecture specific fashion, but on
> aarch64, it contains the ptrauth mask information.
I'm not seeing this kernel patch applied to tip/master or
torvalds/master, what is the status of that part? Then I can look at the
tooling part.
- Arnaldo
> Signed-off-by: Andrew Kilroy <andrew.kilroy at arm.com>
> ---
> arch/arm64/include/asm/arch_sample_data.h | 38 +++++++++++++++++++++++
> arch/arm64/kernel/Makefile | 2 +-
> arch/arm64/kernel/arch_sample_data.c | 37 ++++++++++++++++++++++
> include/linux/perf_event.h | 24 ++++++++++++++
> include/uapi/linux/perf_event.h | 5 ++-
> kernel/events/core.c | 35 +++++++++++++++++++++
> 6 files changed, 139 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm64/include/asm/arch_sample_data.h
> create mode 100644 arch/arm64/kernel/arch_sample_data.c
>
> diff --git a/arch/arm64/include/asm/arch_sample_data.h b/arch/arm64/include/asm/arch_sample_data.h
> new file mode 100644
> index 000000000000..83fda293b1fc
> --- /dev/null
> +++ b/arch/arm64/include/asm/arch_sample_data.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _ASM_ARCH_SAMPLE_DATA_H
> +#define _ASM_ARCH_SAMPLE_DATA_H
> +
> +#include <linux/types.h>
> +
> +/*
> + * Structure holding masks to help userspace stack unwinding
> + * in the presence of arm64 pointer authentication.
> + */
> +struct ptrauth_info {
> + /*
> + * Bits 0, 1, 2, 3, 4 may be set to on, to indicate which keys are being used
> + * The APIAKEY, APIBKEY, APDAKEY, APDBKEY, or the APGAKEY respectively.
> + * Where all bits are off, pointer authentication is not in use for the
> + * process.
> + */
> + u64 enabled_keys;
> +
> + /*
> + * The on bits represent which bits in an instruction pointer
> + * constitute the pointer authentication code.
> + */
> + u64 insn_mask;
> +
> + /*
> + * The on bits represent which bits in a data pointer constitute the
> + * pointer authentication code.
> + */
> + u64 data_mask;
> +};
> +
> +struct arch_sample_data {
> + struct ptrauth_info ptrauth;
> +};
> +
> +#endif
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index fa7981d0d917..843c6e0e2393 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -44,7 +44,7 @@ obj-$(CONFIG_KUSER_HELPERS) += kuser32.o
> obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o
> obj-$(CONFIG_MODULES) += module.o
> obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o
> -obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o
> +obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o arch_sample_data.o
> obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o
> obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> obj-$(CONFIG_CPU_PM) += sleep.o suspend.o
> diff --git a/arch/arm64/kernel/arch_sample_data.c b/arch/arm64/kernel/arch_sample_data.c
> new file mode 100644
> index 000000000000..2d47e8db0dbe
> --- /dev/null
> +++ b/arch/arm64/kernel/arch_sample_data.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <asm/arch_sample_data.h>
> +#include <linux/perf_event.h>
> +
> +inline void perf_output_sample_arch_1(struct perf_output_handle *handle,
> + struct perf_event_header *header,
> + struct perf_sample_data *data,
> + struct perf_event *event)
> +{
> + perf_output_put(handle, data->arch.ptrauth.enabled_keys);
> + perf_output_put(handle, data->arch.ptrauth.insn_mask);
> + perf_output_put(handle, data->arch.ptrauth.data_mask);
> +}
> +
> +inline void perf_prepare_sample_arch_1(struct perf_event_header *header,
> + struct perf_sample_data *data,
> + struct perf_event *event,
> + struct pt_regs *regs)
> +{
> + struct task_struct *task = current;
> + int keys_result = ptrauth_get_enabled_keys(task);
> + u64 user_pac_mask = keys_result > 0 ? ptrauth_user_pac_mask() : 0;
> +
> + data->arch.ptrauth.enabled_keys = keys_result > 0 ? keys_result : 0;
> + data->arch.ptrauth.insn_mask = user_pac_mask;
> + data->arch.ptrauth.data_mask = user_pac_mask;
> +
> + header->size += (3 * sizeof(u64));
> +}
> +
> +inline int perf_event_open_request_arch_1(void)
> +{
> + return 0;
> +}
> +
> +
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index da759560eec5..8a99942989ce 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -999,6 +999,29 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
> extern u64 perf_event_read_value(struct perf_event *event,
> u64 *enabled, u64 *running);
>
> +void perf_output_sample_arch_1(struct perf_output_handle *handle,
> + struct perf_event_header *header,
> + struct perf_sample_data *data,
> + struct perf_event *event);
> +
> +void perf_prepare_sample_arch_1(struct perf_event_header *header,
> + struct perf_sample_data *data,
> + struct perf_event *event,
> + struct pt_regs *regs);
> +
> +int perf_event_open_request_arch_1(void);
> +
> +#if IS_ENABLED(CONFIG_ARM64)
> +
> +#define HAS_ARCH_SAMPLE_DATA
> +#include <asm/arch_sample_data.h>
> +
> +#endif
> +
> +#ifndef HAS_ARCH_SAMPLE_DATA
> +struct arch_sample_data {
> +};
> +#endif
>
> struct perf_sample_data {
> /*
> @@ -1041,6 +1064,7 @@ struct perf_sample_data {
> u64 cgroup;
> u64 data_page_size;
> u64 code_page_size;
> + struct arch_sample_data arch;
> } ____cacheline_aligned;
>
> /* default value for data source */
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index d37629dbad72..821bf5ff6a19 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -162,12 +162,15 @@ enum perf_event_sample_format {
> PERF_SAMPLE_DATA_PAGE_SIZE = 1U << 22,
> PERF_SAMPLE_CODE_PAGE_SIZE = 1U << 23,
> PERF_SAMPLE_WEIGHT_STRUCT = 1U << 24,
> + PERF_SAMPLE_ARCH_1 = 1U << 25,
>
> - PERF_SAMPLE_MAX = 1U << 25, /* non-ABI */
> + PERF_SAMPLE_MAX = 1U << 26, /* non-ABI */
>
> __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /* non-ABI; internal use */
> };
>
> +#define PERF_SAMPLE_ARM64_PTRAUTH PERF_SAMPLE_ARCH_1
> +
> #define PERF_SAMPLE_WEIGHT_TYPE (PERF_SAMPLE_WEIGHT | PERF_SAMPLE_WEIGHT_STRUCT)
> /*
> * values to program into branch_sample_type when PERF_SAMPLE_BRANCH is set
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 80782cddb1da..89ab8120f4f0 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6957,6 +6957,29 @@ static inline bool perf_sample_save_hw_index(struct perf_event *event)
> return event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX;
> }
>
> +#ifndef HAS_ARCH_SAMPLE_DATA
> +
> +inline void perf_output_sample_arch_1(struct perf_output_handle *handle __maybe_unused,
> + struct perf_event_header *header __maybe_unused,
> + struct perf_sample_data *data __maybe_unused,
> + struct perf_event *event __maybe_unused)
> +{
> +}
> +
> +inline void perf_prepare_sample_arch_1(struct perf_event_header *header __maybe_unused,
> + struct perf_sample_data *data __maybe_unused,
> + struct perf_event *event __maybe_unused,
> + struct pt_regs *regs __maybe_unused)
> +{
> +}
> +
> +inline int perf_event_open_request_arch_1(void)
> +{
> + return -EINVAL;
> +}
> +
> +#endif
> +
> void perf_output_sample(struct perf_output_handle *handle,
> struct perf_event_header *header,
> struct perf_sample_data *data,
> @@ -7125,6 +7148,9 @@ void perf_output_sample(struct perf_output_handle *handle,
> perf_aux_sample_output(event, handle, data);
> }
>
> + if (sample_type & PERF_SAMPLE_ARCH_1)
> + perf_output_sample_arch_1(handle, header, data, event);
> +
> if (!event->attr.watermark) {
> int wakeup_events = event->attr.wakeup_events;
>
> @@ -7427,6 +7453,9 @@ void perf_prepare_sample(struct perf_event_header *header,
> if (sample_type & PERF_SAMPLE_CODE_PAGE_SIZE)
> data->code_page_size = perf_get_page_size(data->ip);
>
> + if (sample_type & PERF_SAMPLE_ARCH_1)
> + perf_prepare_sample_arch_1(header, data, event, regs);
> +
> if (sample_type & PERF_SAMPLE_AUX) {
> u64 size;
>
> @@ -12074,6 +12103,12 @@ SYSCALL_DEFINE5(perf_event_open,
> return err;
> }
>
> + if (attr.sample_type & PERF_SAMPLE_ARCH_1) {
> + err = perf_event_open_request_arch_1();
> + if (err)
> + return err;
> + }
> +
> /*
> * In cgroup mode, the pid argument is used to pass the fd
> * opened to the cgroup directory in cgroupfs. The cpu argument
> --
> 2.17.1
--
- Arnaldo
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