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Message-ID: <0f025687-8673-74e1-8f72-737298f931fe@linaro.org>
Date:   Thu, 13 Apr 2023 23:31:21 +0100
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Subject: Re: [PATCH v2 4/6] soc: qcom: Add Qualcomm minidump kernel driver
Content-Language: en-US
To:     Mukesh Ojha <quic_mojha@quicinc.com>, agross@kernel.org,
        andersson@kernel.org, konrad.dybcio@linaro.org, corbet@lwn.net,
        keescook@chromium.org, tony.luck@intel.com, gpiccoli@igalia.com,
        catalin.marinas@arm.com, will@kernel.org
Cc:     linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org
References: <1679491817-2498-1-git-send-email-quic_mojha@quicinc.com>
 <1679491817-2498-5-git-send-email-quic_mojha@quicinc.com>
From:   Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
In-Reply-To: <1679491817-2498-5-git-send-email-quic_mojha@quicinc.com>
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On 22/03/2023 13:30, Mukesh Ojha wrote:
> Minidump is a best effort mechanism to collect useful and predefined
> data for first level of debugging on end user devices running on
> Qualcomm SoCs. It is built on the premise that System on Chip (SoC)
> or subsystem part of SoC crashes, due to a range of hardware and
> software bugs. Hence, the ability to collect accurate data is only
> a best-effort. The data collected could be invalid or corrupted,
> data collection itself could fail, and so on.
> 
> Qualcomm devices in engineering mode provides a mechanism for
> generating full system ramdumps for post mortem debugging. But in some
> cases it's however not feasible to capture the entire content of RAM.
> The minidump mechanism provides the means for selecting region should
> be included in the ramdump. The solution supports extracting the
> ramdump/minidump produced either over USB or stored to an attached
> storage device.
> 
> The core of minidump feature is part of Qualcomm's boot firmware code.
> It initializes shared memory(SMEM), which is a part of DDR and
> allocates a small section of it to minidump table i.e also called
> global table of content (G-ToC). Each subsystem (APSS, ADSP, ...) has
> their own table of segments to be included in the minidump, all
> references from a descriptor in SMEM (G-ToC). Each segment/region has
> some details like name, physical address and it's size etc. and it
> could be anywhere scattered in the DDR.
> 
> Minidump kernel driver adds the capability to add linux region to be
> dumped as part of ram dump collection. It provides appropriate symbol
> to check its enablement and register client regions.
> 
> To simplify post mortem debugging, it creates and maintain an ELF
> header as first region that gets updated upon registration
> of a new region.
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
> ---
>   drivers/soc/qcom/Kconfig         |  14 +
>   drivers/soc/qcom/Makefile        |   1 +
>   drivers/soc/qcom/qcom_minidump.c | 537 +++++++++++++++++++++++++++++++++++++++
>   include/soc/qcom/minidump.h      |  40 +++
>   include/soc/qcom/qcom_minidump.h |  24 +-
>   5 files changed, 615 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/soc/qcom/qcom_minidump.c
>   create mode 100644 include/soc/qcom/minidump.h
> 
> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> index a8f2830..bb0bc32 100644
> --- a/drivers/soc/qcom/Kconfig
> +++ b/drivers/soc/qcom/Kconfig
> @@ -275,4 +275,18 @@ config QCOM_ICC_BWMON
>   	  the fixed bandwidth votes from cpufreq (CPU nodes) thus achieve high
>   	  memory throughput even with lower CPU frequencies.
>   
> +config QCOM_MINIDUMP
> +	tristate "QCOM Minidump Support"
> +	depends on ARCH_QCOM || COMPILE_TEST
> +	select QCOM_SMEM
> +	help
> +	  Enablement of core minidump feature is controlled from boot firmware
> +	  side, and this config allow linux to query and manages APPS minidump
> +	  table.
> +
> +	  Client drivers can register their internal data structures and debug
> +	  messages as part of the minidump region and when the SoC is crashed,
> +	  these selective regions will be dumped instead of the entire DDR.
> +	  This saves significant amount of time and/or storage space.

           To compile this driver as a module, choose M here: the
           module will be called qcom_minidump.

> +
>   endmenu
> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
> index 6e88da8..dc7f0ab 100644
> --- a/drivers/soc/qcom/Makefile
> +++ b/drivers/soc/qcom/Makefile
> @@ -32,3 +32,4 @@ obj-$(CONFIG_QCOM_RPMHPD) += rpmhpd.o
>   obj-$(CONFIG_QCOM_RPMPD) += rpmpd.o
>   obj-$(CONFIG_QCOM_KRYO_L2_ACCESSORS) +=	kryo-l2-accessors.o
>   obj-$(CONFIG_QCOM_ICC_BWMON)	+= icc-bwmon.o
> +obj-$(CONFIG_QCOM_MINIDUMP) += qcom_minidump.o
> diff --git a/drivers/soc/qcom/qcom_minidump.c b/drivers/soc/qcom/qcom_minidump.c
> new file mode 100644
> index 0000000..44770ed
> --- /dev/null
> +++ b/drivers/soc/qcom/qcom_minidump.c
> @@ -0,0 +1,537 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#define pr_fmt(fmt) "Minidump: " fmt
> +
> +#include <linux/init.h>
> +#include <linux/export.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/elf.h>
> +#include <linux/errno.h>
> +#include <linux/io.h>
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <linux/printk.h>
> +#include <linux/soc/qcom/smem.h>
> +#include <soc/qcom/qcom_minidump.h>
> +#include <soc/qcom/minidump.h>
> +
 >snip<
> +/**
> + * DOC: Overview
> + *
> + *   +-----------------------------------------------+
> + *   |   DDR                       +-------------+   |
> + *   |                             |      SS0-ToC|   |
> + *   | +----------------+     +----------------+ |   |
> + *   | |Shared memory   |     |         SS1-ToC| |   |
> + *   | |(SMEM)          |     |                | |   |
> + *   | |                | +-->|--------+       | |   |
> + *   | |G-ToC           | |   | SS-ToC  \      | |   |
> + *   | |+-------------+ | |   | +-----------+  | |   |
> + *   | ||-------------| | |   | |-----------|  | |   |
> + *   | || SS0-ToC     | | | +-|<|SS1 region1|  | |   |
> + *   | ||-------------| | | | | |-----------|  | |   |
> + *   | || SS1-ToC     |-|>+ | | |SS1 region2|  | |   |
> + *   | ||-------------| |   | | |-----------|  | |   |
> + *   | || SS2-ToC     | |   | | |  ...      |  | |   |
> + *   | ||-------------| |   | | |-----------|  | |   |
> + *   | ||  ...        | |   |-|<|SS1 regionN|  | |   |
> + *   | ||-------------| |   | | |-----------|  | |   |
> + *   | || SSn-ToC     | |   | | +-----------+  | |   |
> + *   | |+-------------+ |   | |                | |   |
> + *   | |                |   | |----------------| |   |
> + *   | |                |   +>|  regionN       | |   |
> + *   | |                |   | |----------------| |   |
> + *   | +----------------+   | |                | |   |
> + *   |                      | |----------------| |   |
> + *   |                      +>|  region1       | |   |
> + *   |                        |----------------| |   |
> + *   |                        |                | |   |
> + *   |                        |----------------|-+   |
> + *   |                        |  region5       |     |
> + *   |                        |----------------|     |
> + *   |                        |                |     |
> + *   |  Region information    +----------------+     |
> + *   | +---------------+                             |
> + *   | |region name    |                             |
> + *   | |---------------|                             |
> + *   | |region address |                             |
> + *   | |---------------|                             |
> + *   | |region size    |                             |
> + *   | +---------------+                             |
> + *   +-----------------------------------------------+
> + *       G-ToC: Global table of content
> + *       SS-ToC: Subsystem table of content
> + *       SS0-SSn: Subsystem numbered from 0 to n
> + *
> + * The core of minidump feature is part of Qualcomm's boot firmware code.
> + * It initializes shared memory(SMEM), which is a part of DDR and
> + * allocates a small section of it to minidump table i.e also called
> + * global table of content (G-ToC).
> + *
> + * Each subsystem (APSS, ADSP, ...) has their own table of segments to be
> + * included in the minidump, all references from a descriptor in SMEM
> + * (G-ToC). Each segment/region has some details like name, physical
> + * address and it's size etc. and it could be anywhere scattered
> + * in the DDR.
> + *
> + * Qualcomm SoCs supports extracting the ramdump/minidump produced
> + * either over USB or stored to an attached storage device.
> + */
Isn't the above doc already available in the
  Documentation/admin-guide/qcom_minidump.rst, looks redundant.
> +
> +/**
> + * struct minidump_elfhdr - Minidump table elf header
> + * @ehdr: Elf main header
> + * @shdr: Section header
> + * @phdr: Program header
> + * @elf_offset: Section offset in elf
> + * @strtable_idx: String table current index position
> + */
> +struct minidump_elfhdr {
> +	struct elfhdr		*ehdr;
> +	struct elf_shdr		*shdr;
> +	struct elf_phdr		*phdr;
> +	size_t			elf_offset;
> +	size_t			strtable_idx;
> +};
> +
> +/**
> + * struct minidump - Minidump driver private data
> + * @md_gbl_toc	: Global TOC pointer
> + * @md_ss_toc	: High level OS TOC pointer
> + * @md_regions	: High level OS region base pointer
> + * @elf		: Minidump elf header
> + * @init_done	: Minidump is initialized or not
> + * @ready	: If minidump is ready for the clients.
> + */
> +struct minidump {
> +	struct minidump_global_toc	*md_gbl_toc;
> +	struct minidump_subsystem	*md_ss_toc;
> +	struct minidump_region		*md_regions;
> +	struct minidump_elfhdr		elf;
> +	bool				init_done;
> +	bool				ready;
> +};
> +
> +/*
> + * In some of the Old Qualcomm devices, boot firmware statically allocates 300
> + * as total number of supported region (including all co-processors) in
> + * minidump table out of which linux was using 200. In future, this limitation
> + * from boot firmware might get removed by allocating the region dynamically.
> + * So, keep it compatible with older devices, we can the current limit for Linux
> + * to 200.
> + */
> +#define MAX_NUM_ENTRIES	  200
> +#define MAX_STRTBL_SIZE	  (MAX_NUM_ENTRIES * MAX_REGION_NAME_LENGTH)
> +
> +static struct minidump minidump;
> +static DEFINE_MUTEX(minidump_lock);
> +
> +static struct elf_shdr *elf_shdr_entry_addr(struct elfhdr *ehdr, int idx)
> +{
> +	struct elf_shdr *eshdr = (struct elf_shdr *)((size_t)ehdr + ehdr->e_shoff);
> +
> +	return &eshdr[idx];
> +}
> +
> +static struct elf_phdr *elf_phdr_entry_addr(struct elfhdr *ehdr, int idx)
> +{
> +	struct elf_phdr *ephdr = (struct elf_phdr *)((size_t)ehdr + ehdr->e_phoff);
> +
> +	return &ephdr[idx];
> +}
> +
> +static char *elf_str_table_start(struct elfhdr *ehdr)
> +{
> +	struct elf_shdr *eshdr;
> +
> +	if (ehdr->e_shstrndx == SHN_UNDEF)
> +		return NULL;
> +
> +	eshdr = elf_shdr_entry_addr(ehdr, ehdr->e_shstrndx);
> +	return (char *)ehdr + eshdr->sh_offset;
> +}
> +
> +static unsigned int append_str_to_strtable(const char *name)
> +{
> +	char *strtab = elf_str_table_start(minidump.elf.ehdr);
> +	unsigned int old_idx = minidump.elf.strtable_idx;
> +	unsigned int ret;
> +
> +	if (!strtab || !name)
> +		return 0;
> +
> +	ret = old_idx;
> +	old_idx += strscpy((strtab + old_idx), name, MAX_REGION_NAME_LENGTH);
> +	minidump.elf.strtable_idx = old_idx + 1;
> +	return ret;
> +}
> +
> +static int get_minidump_region_index(const struct qcom_minidump_region *region)
> +{
> +	struct minidump_region *mdr;
> +	unsigned int i;
> +	unsigned int count;
> +
> +	count = le32_to_cpu(minidump.md_ss_toc->region_count);
> +	for (i = 0; i < count; i++) {
> +		mdr = &minidump.md_regions[i];
> +		if (!strcmp(mdr->name, region->name))
> +			return i;
> +	}
> +	return -ENOENT;
> +}
> +

> +/* Update ELF header */

TBH, these type of comments are not adding any value.

> +static void minidump_update_elf_header(const struct qcom_minidump_region *region)
> +{
> +	struct elfhdr *ehdr = minidump.elf.ehdr;
> +	struct elf_shdr *shdr;
> +	struct elf_phdr *phdr;
> +
> +	shdr = elf_shdr_entry_addr(ehdr, ehdr->e_shnum++);
> +	phdr = elf_phdr_entry_addr(ehdr, ehdr->e_phnum++);
> +
> +	shdr->sh_type = SHT_PROGBITS;
> +	shdr->sh_name = append_str_to_strtable(region->name);
> +	shdr->sh_addr = (elf_addr_t)region->virt_addr;
> +	shdr->sh_size = region->size;
> +	shdr->sh_flags = SHF_WRITE;
> +	shdr->sh_offset = minidump.elf.elf_offset;
> +	shdr->sh_entsize = 0;
> +
> +	phdr->p_type = PT_LOAD;
> +	phdr->p_offset = minidump.elf.elf_offset;
> +	phdr->p_vaddr = (elf_addr_t)region->virt_addr;
> +	phdr->p_paddr = region->phys_addr;
> +	phdr->p_filesz = phdr->p_memsz = region->size;
> +	phdr->p_flags = PF_R | PF_W;
> +	minidump.elf.elf_offset += shdr->sh_size;
> +}
> +
> +/* Add region in subsystem ToC */
> +static void minidump_ss_add_region(const struct qcom_minidump_region *region)
> +{
> +	struct minidump_region *mdr;
> +	unsigned int region_cnt = le32_to_cpu(minidump.md_ss_toc->region_count);
> +
> +	mdr = &minidump.md_regions[region_cnt];
> +	strscpy(mdr->name, region->name, sizeof(mdr->name));
> +	mdr->address = cpu_to_le64(region->phys_addr);
> +	mdr->size = cpu_to_le64(region->size);
> +	mdr->valid = cpu_to_le32(MINIDUMP_REGION_VALID);
> +	region_cnt++;
> +	minidump.md_ss_toc->region_count = cpu_to_le32(region_cnt);
> +}
> +
> +static bool qcom_minidump_valid_region(const struct qcom_minidump_region *region)
> +{
> +	return region &&
> +		strnlen(region->name, MAX_NAME_LENGTH) < MAX_NAME_LENGTH &&
> +		region->virt_addr &&
> +		region->size &&
> +		IS_ALIGNED(region->size, 4);
> +}
> +
> +static int minidump_add_elf_header(void)
> +{
> +	struct qcom_minidump_region elfregion;
> +	struct elfhdr *ehdr;
> +	struct elf_shdr *shdr;
> +	struct elf_phdr *phdr;
> +	unsigned int  elfh_size;
> +	unsigned int strtbl_off;
> +	unsigned int phdr_off;
> +	char *banner;
> +	unsigned int banner_len;
> +
> +	banner_len = strlen(linux_banner);
> +	/*
> +	 * Header buffer contains:
> +	 * ELF header, (MAX_NUM_ENTRIES + 4) of Section and Program ELF headers,
> +	 * where, 4 additional entries, one for empty header, one for string table
> +	 * one for minidump table and one for linux banner.
> +	 *
> +	 * Linux banner is stored in minidump to aid post mortem tools to determine
> +	 * the kernel version.
> +	 */
> +	elfh_size = sizeof(*ehdr);
> +	elfh_size += MAX_STRTBL_SIZE;
> +	elfh_size += banner_len + 1;
> +	elfh_size += ((sizeof(*shdr) + sizeof(*phdr)) * (MAX_NUM_ENTRIES + 4));
> +	elfh_size = ALIGN(elfh_size, 4);
> +
> +	minidump.elf.ehdr = kzalloc(elfh_size, GFP_KERNEL);
> +	if (!minidump.elf.ehdr)
> +		return -ENOMEM;
> +
> +	/* Register ELF header as first region */
> +	strscpy(elfregion.name, "KELF_HEADER", sizeof(elfregion.name));
> +	elfregion.virt_addr = minidump.elf.ehdr;
> +	elfregion.phys_addr = virt_to_phys(minidump.elf.ehdr);
> +	elfregion.size = elfh_size;
> +	minidump_ss_add_region(&elfregion);
> +
> +	ehdr = minidump.elf.ehdr;
> +	/* Assign Section/Program headers offset */
> +	minidump.elf.shdr = shdr = (struct elf_shdr *)(ehdr + 1);
> +	minidump.elf.phdr = phdr = (struct elf_phdr *)(shdr + MAX_NUM_ENTRIES);
> +	phdr_off = sizeof(*ehdr) + (sizeof(*shdr) * MAX_NUM_ENTRIES);
> +
> +	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
> +	ehdr->e_ident[EI_CLASS] = ELF_CLASS;
> +	ehdr->e_ident[EI_DATA] = ELF_DATA;
> +	ehdr->e_ident[EI_VERSION] = EV_CURRENT;
> +	ehdr->e_ident[EI_OSABI] = ELF_OSABI;
> +	ehdr->e_type = ET_CORE;
> +	ehdr->e_machine  = ELF_ARCH;
> +	ehdr->e_version = EV_CURRENT;
> +	ehdr->e_ehsize = sizeof(*ehdr);
> +	ehdr->e_phoff = phdr_off;
> +	ehdr->e_phentsize = sizeof(*phdr);
> +	ehdr->e_shoff = sizeof(*ehdr);
> +	ehdr->e_shentsize = sizeof(*shdr);
> +	ehdr->e_shstrndx = 1;
> +
> +	minidump.elf.elf_offset = elfh_size;
> +
> +	/*
> +	 * The zeroth index of the section header is reserved and is rarely used.
> +	 * Set the section header as null (SHN_UNDEF) and move to the next one.
> +	 * 2nd Section is String table.
> +	 */
> +	minidump.elf.strtable_idx = 1;
> +	strtbl_off = sizeof(*ehdr) + ((sizeof(*phdr) + sizeof(*shdr)) * MAX_NUM_ENTRIES);
> +	shdr++;
> +	shdr->sh_type = SHT_STRTAB;
> +	shdr->sh_offset = (elf_addr_t)strtbl_off;
> +	shdr->sh_size = MAX_STRTBL_SIZE;
> +	shdr->sh_entsize = 0;
> +	shdr->sh_flags = 0;
> +	shdr->sh_name = append_str_to_strtable("STR_TBL");
> +	shdr++;
> +
> +	/* 3rd Section is for Minidump_table VA, used by parsers */
> +	shdr->sh_type = SHT_PROGBITS;
> +	shdr->sh_entsize = 0;
> +	shdr->sh_flags = 0;
> +	shdr->sh_addr = (elf_addr_t)&minidump;
> +	shdr->sh_name = append_str_to_strtable("minidump_table");
> +	shdr++;
> +
> +	/* 4th Section is Linux banner */
> +	banner = (char *)ehdr + strtbl_off + MAX_STRTBL_SIZE;
> +	memcpy(banner, linux_banner, banner_len);
> +
> +	shdr->sh_type = SHT_PROGBITS;
> +	shdr->sh_offset = (elf_addr_t)(strtbl_off + MAX_STRTBL_SIZE);
> +	shdr->sh_size = banner_len + 1;
> +	shdr->sh_addr = (elf_addr_t)linux_banner;
> +	shdr->sh_entsize = 0;
> +	shdr->sh_flags = SHF_WRITE;
> +	shdr->sh_name = append_str_to_strtable("linux_banner");
> +
> +	phdr->p_type = PT_LOAD;
> +	phdr->p_offset = (elf_addr_t)(strtbl_off + MAX_STRTBL_SIZE);
> +	phdr->p_vaddr = (elf_addr_t)linux_banner;
> +	phdr->p_paddr = virt_to_phys(linux_banner);
> +	phdr->p_filesz = phdr->p_memsz = banner_len + 1;
> +	phdr->p_flags = PF_R | PF_W;
> +
> +	/* Update the program header/section header count added above */
> +	ehdr->e_phnum = 1;
> +	ehdr->e_shnum = 4;
> +
> +	return 0;
> +}
> +
> +static int qcom_minidump_init(void)
> +{
> +	struct minidump_subsystem *mdsstoc;
> +
> +	mdsstoc = qcom_minidump_subsystem_desc(MINIDUMP_APSS_DESC);
> +	if (IS_ERR(mdsstoc))
> +		return -EINVAL;
> +
> +	minidump.md_regions = kcalloc(MAX_NUM_ENTRIES,
> +			      sizeof(struct minidump_region), GFP_KERNEL);
> +	if (!minidump.md_regions)
> +		return -ENOMEM;
> +
> +	minidump.md_ss_toc = mdsstoc;
> +	/* Share memory table update */
> +	mdsstoc->regions_baseptr = cpu_to_le64(virt_to_phys(minidump.md_regions));
> +	/* Tell bootloader not to encrypt the regions of this subsystem */
> +	mdsstoc->encryption_status = cpu_to_le32(MINIDUMP_SS_ENCR_DONE);
> +	mdsstoc->encryption_required = cpu_to_le32(MINIDUMP_SS_ENCR_NOTREQ);
> +
> +	mdsstoc->enabled = cpu_to_le32(MINIDUMP_SS_ENABLED);
> +	mdsstoc->status = cpu_to_le32(1);
> +	mdsstoc->region_count = cpu_to_le32(0);
> +
> +	return 0;
> +}
> +
> +/**
> + * qcom_minidump_ready - Check, if minidump is ready for client registration or not.
> + *
> + * Return: zero on success and negative on failure.
> + *
> + * Qualcomm minidump feature is dependent on Qualcomm's shared memory and it is
> + * possible for a arm64 target to not have it's device tree entry present, for
> + * such case, qcom_minidump_ready() returns -ENODEV and client should not further
> + * try to register their region with minidump driver.
> + */
> +int qcom_minidump_ready(void)

return type can be bool instead of int.
> +{
> +	struct device_node *np;
> +	void *ptr;
> +	int ret = 0;
> +
> +	mutex_lock(&minidump_lock);
> +	if (minidump.ready)
> +		goto unlock;
> +

<--
> +	np = of_find_compatible_node(NULL, NULL, "qcom,smem");
> +	if (!np) {
> +		ret = -ENODEV;
> +		goto unlock;
> +	}
> +
> +	of_node_put(np);
> +	if (!of_device_is_available(np)) {
> +		ret = -EPROBE_DEFER;
> +		goto unlock;
> +	}
> +
-->

Above snippet looks redundant as qcom_smem_get will already check for 
the above.

> +	ptr = qcom_smem_get(QCOM_SMEM_HOST_ANY, SBL_MINIDUMP_SMEM_ID, NULL);
> +	if (IS_ERR(ptr)) {
> +		ret = PTR_ERR(ptr);
> +		goto unlock;
> +	}
> +
> +	minidump.md_gbl_toc = ptr;
> +	minidump.ready = true;
> +
> +unlock:
> +	if (ret < 0)
> +		minidump.ready = false;
> +	mutex_unlock(&minidump_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(qcom_minidump_ready);
> +
> +/**
> + * qcom_minidump_subsystem_desc() - Get minidump subsystem descriptor.
> + * @minidump_index: minidump index for a subsystem in minidump table
> + *
> + * Return: minidump subsystem descriptor address on success and error
> + * on failure
> + */
> +struct minidump_subsystem *qcom_minidump_subsystem_desc(unsigned int minidump_index)
> +{
> +	struct minidump_global_toc *mdgtoc;
> +	size_t size;
> +
> +	if (minidump.md_gbl_toc)
> +		return &minidump.md_gbl_toc->subsystems[minidump_index];
> +
Why would we end up here, if the user is supposed to call 
qcom_minidump_ready() before calling this qcom_minidump_subsystem_desc()

A check for minidump.ready should do the job.
I also see locking is missing.

> +	mdgtoc = qcom_smem_get(QCOM_SMEM_HOST_ANY, SBL_MINIDUMP_SMEM_ID, &size);
> +	if (IS_ERR(mdgtoc)) {
> +		pr_err("Unable to find minidump smem item\n");
> +		return ERR_CAST(mdgtoc);
> +	}
> +
> +	if (size < sizeof(*mdgtoc) || !mdgtoc->status) {
> +		pr_err("Minidump table is not initialized\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return &mdgtoc->subsystems[minidump_index];
> +}
> +EXPORT_SYMBOL_GPL(qcom_minidump_subsystem_desc);
> +
> +/**
> + * qcom_minidump_region_register() - Register a region in Minidump table.
What happens if lets say a driver calls qcom_minidump_region_register() 
on every probe and driver is loaded and unloaded multiple times, we will 
endup with stale pointers for that region phys_addr comes from 
dynamically allocated region.
Is there a reason why we do not have a  qcom_minidump_region_unregister() ?


> + * @region: minidump region.
> + *
> + * Client should not call this directly instead first call qcom_minidump_ready()
> + * to check if minidump is ready to do registration if yes, then call this API.
> + *
> + * Return: On success, it returns region index in minidump table and negative
> + * error value on failure.
> + */
> +int qcom_minidump_region_register(const struct qcom_minidump_region *region)
> +{
> +	unsigned int num_region;
> +	int ret;
> +
> +	mutex_lock(&minidump_lock);
> +	if (!minidump.ready) {
> +		pr_info("minidump is not ready\n");
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	/* Initialize minidump context on first call */
> +	if (!minidump.init_done) {
> +		ret = qcom_minidump_init();
> +		if (ret)
> +			goto unlock;
> +
> +		/* First entry would be ELF header */
> +		ret = minidump_add_elf_header();
> +		if (ret) {
> +			kfree(minidump.md_regions);
> +			goto unlock;
> +		}
> +
> +		minidump.init_done = true;
> +	}
> +
> +	if (!qcom_minidump_valid_region(region)) {
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	ret = get_minidump_region_index(region);
> +	if (ret >= 0) {
> +		pr_info("%s region is already registered\n", region->name);
> +		ret = -EEXIST;
> +		goto unlock;
> +	}
> +
> +	/* Check if there is a room for a new entry */
> +	ret = num_region = le32_to_cpu(minidump.md_ss_toc->region_count);
> +	if (num_region >= MAX_NUM_ENTRIES) {
> +		pr_err("maximum region limit %u reached\n", num_region);
> +		ret = -ENOSPC;
> +		goto unlock;
> +	}
> +
> +	minidump_ss_add_region(region);
> +	minidump_update_elf_header(region);
> +unlock:
> +	mutex_unlock(&minidump_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(qcom_minidump_region_register);
> +
> +static void __exit qcom_minidump_exit(void)
> +{
> +	mutex_lock(&minidump_lock);
> +	kfree(minidump.elf.ehdr);
> +	kfree(minidump.md_regions);

AFAIU, if minidump driver is unloaded then we will endup with stale 
pointers in smem.

> +	mutex_unlock(&minidump_lock);
> +}
> +module_exit(qcom_minidump_exit);
> +
> +MODULE_DESCRIPTION("Qualcomm minidump driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/soc/qcom/minidump.h b/include/soc/qcom/minidump.h

include/soc/qcom/qcom_minidump.h should be merged with 
include/soc/qcom/minidump.h, I see no point in having two headers for 
same thing.


> new file mode 100644
> index 0000000..a50843f
> --- /dev/null
> +++ b/include/soc/qcom/minidump.h
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef _MINIDUMP_H_
> +#define _MINIDUMP_H_
> +
> +#include <linux/types.h>
> +
> +#define MAX_NAME_LENGTH		12
> +
> +/**
> + * struct qcom_minidump_region - Minidump region information
> + *
> + * @name:	Entry name, Minidump will dump binary with this name.
> + * @virt_addr:  Virtual address of the entry.
> + * @phys_addr:	Physical address of the entry to dump.
> + * @size:	Number of byte to dump from @address location,
> + *		and it should be 4 byte aligned.
> + */
> +struct qcom_minidump_region {
> +	char		name[MAX_NAME_LENGTH];
> +	void		*virt_addr;
> +	phys_addr_t	phys_addr;
> +	size_t		size;
> +};
> +
> +#if IS_ENABLED(CONFIG_QCOM_MINIDUMP)
> +extern int qcom_minidump_ready(void);
> +extern int qcom_minidump_region_register(const struct qcom_minidump_region *entry);
> +#else
> +static inline int qcom_minidump_ready(void) { return 0; }
> +static inline int qcom_minidump_region_register(const struct qcom_minidump_region *entry)
> +{
> +	/* Return quietly, if minidump is not enabled */
> +	return 0;
> +}
> +#endif
> +#endif /* _MINIDUMP_H_ */
> diff --git a/include/soc/qcom/qcom_minidump.h b/include/soc/qcom/qcom_minidump.h
> index 84c8605..e8630ed 100644
> --- a/include/soc/qcom/qcom_minidump.h
> +++ b/include/soc/qcom/qcom_minidump.h
> @@ -10,11 +10,25 @@
>   
>   #define MAX_NUM_OF_SS           10
>   #define MAX_REGION_NAME_LENGTH  16
> +
> +#define MINIDUMP_REVISION	1
>   #define SBL_MINIDUMP_SMEM_ID	602
> +
> +/* Application processor minidump descriptor */
> +#define MINIDUMP_APSS_DESC	0
> +#define SMEM_ENTRY_SIZE		40
> +
>   #define MINIDUMP_REGION_VALID		('V' << 24 | 'A' << 16 | 'L' << 8 | 'I' << 0)
> +#define MINIDUMP_REGION_INVALID		('I' << 24 | 'N' << 16 | 'V' << 8 | 'A' << 0)
> +#define MINIDUMP_REGION_INIT		('I' << 24 | 'N' << 16 | 'I' << 8 | 'T' << 0)
> +#define MINIDUMP_REGION_NOINIT		0
> +
> +#define MINIDUMP_SS_ENCR_REQ		(0 << 24 | 'Y' << 16 | 'E' << 8 | 'S' << 0)
> +#define MINIDUMP_SS_ENCR_NOTREQ		(0 << 24 | 0 << 16 | 'N' << 8 | 'R' << 0)
> +#define MINIDUMP_SS_ENCR_NONE		('N' << 24 | 'O' << 16 | 'N' << 8 | 'E' << 0)
>   #define MINIDUMP_SS_ENCR_DONE		('D' << 24 | 'O' << 16 | 'N' << 8 | 'E' << 0)
> +#define MINIDUMP_SS_ENCR_START		('S' << 24 | 'T' << 16 | 'R' << 8 | 'T' << 0)
>   #define MINIDUMP_SS_ENABLED		('E' << 24 | 'N' << 16 | 'B' << 8 | 'L' << 0)
> -
>   /**
>    * struct minidump_region - Minidump region
>    * @name		: Name of the region to be dumped
> @@ -63,4 +77,12 @@ struct minidump_global_toc {
>   	struct minidump_subsystem	subsystems[MAX_NUM_OF_SS];
>   };
>   
> +#if IS_ENABLED(CONFIG_QCOM_MINIDUMP)
> +extern struct minidump_subsystem *qcom_minidump_subsystem_desc(unsigned int minidump_index);
> +#else
> +static inline struct minidump_subsystem *qcom_minidump_subsystem_desc(unsigned int minidump_index)
> +{
> +	return NULL;
> +}
> +#endif
>   #endif  /* _QCOM_MINIDUMP_H_ */