Re: [PATCH v3 26/26] meminspect: Add debug kinfo compatible driver

[Petr Pavlu <petr.pavlu@suse.com>]

On 7/8/26 9:08 AM, Mukesh Ojha wrote:
> From: Eugen Hristev <eugen.hristev@linaro.org>
> 
> With this driver, the registered regions are copied to a shared memory
> zone at register time. The shared memory zone is supplied via OF. This
> driver will select only regions that are of interest, and keep only
> addresses. The format of the list is Kinfo compatible, with devices like
> Google Pixel phone. The firmware is only interested in some symbols'
> addresses.
> 
> Signed-off-by: Eugen Hristev <eugen.hristev@linaro.org>
> Signed-off-by: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>
> ---
[...]
> diff --git a/kernel/meminspect/kinfo.c b/kernel/meminspect/kinfo.c
> new file mode 100644
> index 000000000000..7451c13bc316
> --- /dev/null
> +++ b/kernel/meminspect/kinfo.c
> @@ -0,0 +1,257 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + *
> + * Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
> + * Copyright 2021 Google LLC
> + * Copyright 2025 Linaro Ltd. Eugen Hristev <eugen.hristev@linaro.org>
> + */
> +#include <linux/container_of.h>
> +#include <linux/kallsyms.h>
> +#include <linux/meminspect.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_reserved_mem.h>
> +#include <linux/platform_device.h>
> +#include <linux/utsname.h>
> +
> +#define BUILD_INFO_LEN		256
> +#define DEBUG_KINFO_MAGIC	0xcceeddff
> +
> +/*
> + * Header structure must be byte-packed, since the table is provided to
> + * bootloader.
> + */
> +struct kernel_info {
> +	/* For kallsyms */
> +	u8 enabled_all;
> +	u8 enabled_base_relative;
> +	u8 enabled_absolute_percpu;
> +	u8 enabled_cfi_clang;
> +	u32 num_syms;
> +	u16 name_len;
> +	u16 bit_per_long;
> +	u16 module_name_len;
> +	u16 symbol_len;
> +	u64 _relative_pa;
> +	u64 _text_pa;
> +	u64 _stext_pa;
> +	u64 _etext_pa;
> +	u64 _sinittext_pa;
> +	u64 _einittext_pa;
> +	u64 _end_pa;
> +	u64 _offsets_pa;
> +	u64 _names_pa;
> +	u64 _token_table_pa;
> +	u64 _token_index_pa;
> +	u64 _markers_pa;
> +	u64 _seqs_of_names_pa;
> +
> +	/* For frame pointer */
> +	u32 thread_size;
> +
> +	/* For virt_to_phys */
> +	u64 swapper_pg_dir_pa;
> +
> +	/* For linux banner */
> +	u8 last_uts_release[__NEW_UTS_LEN];
> +
> +	/* For module kallsyms */
> +	u32 enabled_modules_tree_lookup;
> +	u32 mod_mem_offset;
> +	u32 mod_kallsyms_offset;
> +} __packed;

Is this kinfo format documented anywhere? I was only able to find
a reference to the equivalent downstream Android driver [1] in the cover
letter. However, I don't quite understand what it is or what the
associated bootloader component does with this information. In
particular, I'm unclear about the purpose of the following
module-related fields:

module_name_len
enabled_modules_tree_lookup
mod_mem_offset
mod_kallsyms_offset

These appear to be exposed for reading the internals of the module
loader. Be aware that this data is not stable.

[1] https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/drivers/android/debug_kinfo.c

-- 
Thanks,
Petr