Re: [PATCH v8 2/4] remoteproc: coredump: Add minidump functionality

From: Bjorn Andersson
Date: Fri Nov 20 2020 - 23:03:46 EST

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In reply to: Siddharth Gupta: "[PATCH v8 2/4] remoteproc: coredump: Add minidump functionality"
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On Thu 19 Nov 15:05 CST 2020, Siddharth Gupta wrote:

> This change adds a new kind of core dump mechanism which instead of dumping
> entire program segments of the firmware, dumps sections of the remoteproc
> memory which are sufficient to allow debugging the firmware. This function
> thus uses section headers instead of program headers during creation of the
> core dump elf.
>
> Co-developed-by: Rishabh Bhatnagar <rishabhb@xxxxxxxxxxxxxx>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@xxxxxxxxxxxxxx>
> Signed-off-by: Siddharth Gupta <sidgup@xxxxxxxxxxxxxx>

Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

Regards,
Bjorn

> ---
> drivers/remoteproc/remoteproc_coredump.c | 140 ++++++++++++++++++++++++++++
> drivers/remoteproc/remoteproc_elf_helpers.h | 26 ++++++
> include/linux/remoteproc.h | 1 +
> 3 files changed, 167 insertions(+)
>
> diff --git a/drivers/remoteproc/remoteproc_coredump.c b/drivers/remoteproc/remoteproc_coredump.c
> index 34530dc..81ec154 100644
> --- a/drivers/remoteproc/remoteproc_coredump.c
> +++ b/drivers/remoteproc/remoteproc_coredump.c
> @@ -323,3 +323,143 @@ void rproc_coredump(struct rproc *rproc)
> */
> wait_for_completion(&dump_state.dump_done);
> }
> +
> +/**
> + * rproc_coredump_using_sections() - perform coredump using section headers
> + * @rproc: rproc handle
> + *
> + * This function will generate an ELF header for the registered sections of
> + * segments and create a devcoredump device associated with rproc. Based on
> + * the coredump configuration this function will directly copy the segments
> + * from device memory to userspace or copy segments from device memory to
> + * a separate buffer, which can then be read by userspace.
> + * The first approach avoids using extra vmalloc memory. But it will stall
> + * recovery flow until dump is read by userspace.
> + */
> +void rproc_coredump_using_sections(struct rproc *rproc)
> +{
> + struct rproc_dump_segment *segment;
> + void *shdr;
> + void *ehdr;
> + size_t data_size;
> + size_t strtbl_size = 0;
> + size_t strtbl_index = 1;
> + size_t offset;
> + void *data;
> + u8 class = rproc->elf_class;
> + int shnum;
> + struct rproc_coredump_state dump_state;
> + unsigned int dump_conf = rproc->dump_conf;
> + char *str_tbl = "STR_TBL";
> +
> + if (list_empty(&rproc->dump_segments) ||
> + dump_conf == RPROC_COREDUMP_DISABLED)
> + return;
> +
> + if (class == ELFCLASSNONE) {
> + dev_err(&rproc->dev, "Elf class is not set\n");
> + return;
> + }
> +
> + /*
> + * We allocate two extra section headers. The first one is null.
> + * Second section header is for the string table. Also space is
> + * allocated for string table.
> + */
> + data_size = elf_size_of_hdr(class) + 2 * elf_size_of_shdr(class);
> + shnum = 2;
> +
> + /* the extra byte is for the null character at index 0 */
> + strtbl_size += strlen(str_tbl) + 2;
> +
> + list_for_each_entry(segment, &rproc->dump_segments, node) {
> + data_size += elf_size_of_shdr(class);
> + strtbl_size += strlen(segment->priv) + 1;
> + if (dump_conf == RPROC_COREDUMP_ENABLED)
> + data_size += segment->size;
> + shnum++;
> + }
> +
> + data_size += strtbl_size;
> +
> + data = vmalloc(data_size);
> + if (!data)
> + return;
> +
> + ehdr = data;
> + memset(ehdr, 0, elf_size_of_hdr(class));
> + /* e_ident field is common for both elf32 and elf64 */
> + elf_hdr_init_ident(ehdr, class);
> +
> + elf_hdr_set_e_type(class, ehdr, ET_CORE);
> + elf_hdr_set_e_machine(class, ehdr, rproc->elf_machine);
> + elf_hdr_set_e_version(class, ehdr, EV_CURRENT);
> + elf_hdr_set_e_entry(class, ehdr, rproc->bootaddr);
> + elf_hdr_set_e_shoff(class, ehdr, elf_size_of_hdr(class));
> + elf_hdr_set_e_ehsize(class, ehdr, elf_size_of_hdr(class));
> + elf_hdr_set_e_shentsize(class, ehdr, elf_size_of_shdr(class));
> + elf_hdr_set_e_shnum(class, ehdr, shnum);
> + elf_hdr_set_e_shstrndx(class, ehdr, 1);
> +
> + /*
> + * 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.
> + */
> + shdr = data + elf_hdr_get_e_shoff(class, ehdr);
> + memset(shdr, 0, elf_size_of_shdr(class));
> + shdr += elf_size_of_shdr(class);
> +
> + /* Initialize the string table. */
> + offset = elf_hdr_get_e_shoff(class, ehdr) +
> + elf_size_of_shdr(class) * elf_hdr_get_e_shnum(class, ehdr);
> + memset(data + offset, 0, strtbl_size);
> +
> + /* Fill in the string table section header. */
> + memset(shdr, 0, elf_size_of_shdr(class));
> + elf_shdr_set_sh_type(class, shdr, SHT_STRTAB);
> + elf_shdr_set_sh_offset(class, shdr, offset);
> + elf_shdr_set_sh_size(class, shdr, strtbl_size);
> + elf_shdr_set_sh_entsize(class, shdr, 0);
> + elf_shdr_set_sh_flags(class, shdr, 0);
> + elf_shdr_set_sh_name(class, shdr, elf_strtbl_add(str_tbl, ehdr, class, &strtbl_index));
> + offset += elf_shdr_get_sh_size(class, shdr);
> + shdr += elf_size_of_shdr(class);
> +
> + list_for_each_entry(segment, &rproc->dump_segments, node) {
> + memset(shdr, 0, elf_size_of_shdr(class));
> + elf_shdr_set_sh_type(class, shdr, SHT_PROGBITS);
> + elf_shdr_set_sh_offset(class, shdr, offset);
> + elf_shdr_set_sh_addr(class, shdr, segment->da);
> + elf_shdr_set_sh_size(class, shdr, segment->size);
> + elf_shdr_set_sh_entsize(class, shdr, 0);
> + elf_shdr_set_sh_flags(class, shdr, SHF_WRITE);
> + elf_shdr_set_sh_name(class, shdr,
> + elf_strtbl_add(segment->priv, ehdr, class, &strtbl_index));
> +
> + /* No need to copy segments for inline dumps */
> + if (dump_conf == RPROC_COREDUMP_ENABLED)
> + rproc_copy_segment(rproc, data + offset, segment, 0,
> + segment->size);
> + offset += elf_shdr_get_sh_size(class, shdr);
> + shdr += elf_size_of_shdr(class);
> + }
> +
> + if (dump_conf == RPROC_COREDUMP_ENABLED) {
> + dev_coredumpv(&rproc->dev, data, data_size, GFP_KERNEL);
> + return;
> + }
> +
> + /* Initialize the dump state struct to be used by rproc_coredump_read */
> + dump_state.rproc = rproc;
> + dump_state.header = data;
> + init_completion(&dump_state.dump_done);
> +
> + dev_coredumpm(&rproc->dev, NULL, &dump_state, data_size, GFP_KERNEL,
> + rproc_coredump_read, rproc_coredump_free);
> +
> + /* Wait until the dump is read and free is called. Data is freed
> + * by devcoredump framework automatically after 5 minutes.
> + */
> + wait_for_completion(&dump_state.dump_done);
> +}
> +EXPORT_SYMBOL(rproc_coredump_using_sections);
> diff --git a/drivers/remoteproc/remoteproc_elf_helpers.h b/drivers/remoteproc/remoteproc_elf_helpers.h
> index 4b6be7b..26404e6 100644
> --- a/drivers/remoteproc/remoteproc_elf_helpers.h
> +++ b/drivers/remoteproc/remoteproc_elf_helpers.h
> @@ -65,6 +65,7 @@ ELF_GEN_FIELD_GET_SET(hdr, e_type, u16)
> ELF_GEN_FIELD_GET_SET(hdr, e_version, u32)
> ELF_GEN_FIELD_GET_SET(hdr, e_ehsize, u32)
> ELF_GEN_FIELD_GET_SET(hdr, e_phentsize, u16)
> +ELF_GEN_FIELD_GET_SET(hdr, e_shentsize, u16)
>
> ELF_GEN_FIELD_GET_SET(phdr, p_paddr, u64)
> ELF_GEN_FIELD_GET_SET(phdr, p_vaddr, u64)
> @@ -75,6 +76,9 @@ ELF_GEN_FIELD_GET_SET(phdr, p_offset, u64)
> ELF_GEN_FIELD_GET_SET(phdr, p_flags, u32)
> ELF_GEN_FIELD_GET_SET(phdr, p_align, u64)
>
> +ELF_GEN_FIELD_GET_SET(shdr, sh_type, u32)
> +ELF_GEN_FIELD_GET_SET(shdr, sh_flags, u32)
> +ELF_GEN_FIELD_GET_SET(shdr, sh_entsize, u16)
> ELF_GEN_FIELD_GET_SET(shdr, sh_size, u64)
> ELF_GEN_FIELD_GET_SET(shdr, sh_offset, u64)
> ELF_GEN_FIELD_GET_SET(shdr, sh_name, u32)
> @@ -93,4 +97,26 @@ ELF_STRUCT_SIZE(shdr)
> ELF_STRUCT_SIZE(phdr)
> ELF_STRUCT_SIZE(hdr)
>
> +static inline unsigned int elf_strtbl_add(const char *name, void *ehdr, u8 class, size_t *index)
> +{
> + u16 shstrndx = elf_hdr_get_e_shstrndx(class, ehdr);
> + void *shdr;
> + char *strtab;
> + size_t idx, ret;
> +
> + shdr = ehdr + elf_size_of_hdr(class) + shstrndx * elf_size_of_shdr(class);
> + strtab = ehdr + elf_shdr_get_sh_offset(class, shdr);
> + idx = index ? *index : 0;
> + if (!strtab || !name)
> + return 0;
> +
> + ret = idx;
> + strcpy((strtab + idx), name);
> + idx += strlen(name) + 1;
> + if (index)
> + *index = idx;
> +
> + return ret;
> +}
> +
> #endif /* REMOTEPROC_ELF_LOADER_H */
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index a419878..cdf2722 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -656,6 +656,7 @@ rproc_of_resm_mem_entry_init(struct device *dev, u32 of_resm_idx, size_t len,
> int rproc_boot(struct rproc *rproc);
> void rproc_shutdown(struct rproc *rproc);
> void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type);
> +void rproc_coredump_using_sections(struct rproc *rproc);
> int rproc_coredump_add_segment(struct rproc *rproc, dma_addr_t da, size_t size);
> int rproc_coredump_add_custom_segment(struct rproc *rproc,
> dma_addr_t da, size_t size,
> --
> Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>

Next message: Bjorn Andersson: "Re: [PATCH v8 3/4] remoteproc: qcom: Add capability to collect minidumps"
Previous message: Bjorn Andersson: "Re: [PATCH v8 1/4] remoteproc: core: Add ops to enable custom coredump functionality"
In reply to: Siddharth Gupta: "[PATCH v8 2/4] remoteproc: coredump: Add minidump functionality"
Next in thread: Siddharth Gupta: "[PATCH v8 4/4] remoteproc: qcom: Add minidump id for sm8150 modem"
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