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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id v11sm4305971otj.73.2020.10.26.14.09.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2020 14:09:14 -0700 (PDT) Date: Mon, 26 Oct 2020 16:09:12 -0500 From: Bjorn Andersson To: Siddharth Gupta Cc: agross@kernel.org, ohad@wizery.com, linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tsoni@codeaurora.org, psodagud@codeaurora.org, rishabhb@codeaurora.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v6 2/4] remoteproc: coredump: Add minidump functionality Message-ID: <20201026210912.GA4611@builder.lan> References: <1601690757-25726-1-git-send-email-sidgup@codeaurora.org> <1601690757-25726-3-git-send-email-sidgup@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1601690757-25726-3-git-send-email-sidgup@codeaurora.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 02 Oct 21:05 CDT 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. > > Signed-off-by: Rishabh Bhatnagar > Signed-off-by: Siddharth Gupta > --- > drivers/remoteproc/remoteproc_coredump.c | 132 ++++++++++++++++++++++++++++ > drivers/remoteproc/remoteproc_elf_helpers.h | 27 ++++++ > include/linux/remoteproc.h | 1 + > 3 files changed, 160 insertions(+) > > diff --git a/drivers/remoteproc/remoteproc_coredump.c b/drivers/remoteproc/remoteproc_coredump.c > index bb15a29..e7d1394 100644 > --- a/drivers/remoteproc/remoteproc_coredump.c > +++ b/drivers/remoteproc/remoteproc_coredump.c > @@ -13,6 +13,8 @@ > #include "remoteproc_internal.h" > #include "remoteproc_elf_helpers.h" > > +#define MAX_STRTBL_SIZE 512 > + > struct rproc_coredump_state { > struct rproc *rproc; > void *header; > @@ -323,3 +325,133 @@ void rproc_coredump(struct rproc *rproc) > */ > wait_for_completion(&dump_state.dump_done); > } > + > +/** > + * rproc_minidump() - perform minidump > + * @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_minidump(struct rproc *rproc) Just to confirm, this does the same thing as rproc_coredump() with the difference that instead of storing the segments in program headers, you reference them using section headers? > +{ > + struct rproc_dump_segment *segment; > + void *shdr; > + void *ehdr; > + size_t data_size; > + 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) + > + MAX_STRTBL_SIZE; Once you start populating the string table there's no checks that this isn't overrun. But really > + shnum = 2; > + > + list_for_each_entry(segment, &rproc->dump_segments, node) { > + data_size += elf_size_of_shdr(class); > + if (dump_conf == RPROC_COREDUMP_DEFAULT) > + data_size += segment->size; > + shnum++; > + } > + > + 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); > + > + /* Set the first section header as null 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, MAX_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, MAX_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, set_section_name(str_tbl, ehdr, class)); > + offset += elf_shdr_get_sh_size(class, shdr); > + shdr += elf_size_of_shdr(class); I assume this last part creates the null entry? How about mentioning that in a comment - and perhaps why there needs to be a null entry. > + > + 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, > + set_section_name(segment->priv, ehdr, class)); > + > + /* No need to copy segments for inline dumps */ > + if (dump_conf == RPROC_COREDUMP_DEFAULT) > + 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_DEFAULT) { > + 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_minidump); > diff --git a/drivers/remoteproc/remoteproc_elf_helpers.h b/drivers/remoteproc/remoteproc_elf_helpers.h > index 4b6be7b..d83ebca 100644 > --- a/drivers/remoteproc/remoteproc_elf_helpers.h > +++ b/drivers/remoteproc/remoteproc_elf_helpers.h > @@ -11,6 +11,7 @@ > #include > #include > > +#define MAX_NAME_LENGTH 16 This name is too generic. Why is it 16? > +static inline unsigned int set_section_name(const char *name, void *ehdr, > + u8 class) > +{ > + u16 shstrndx = elf_hdr_get_e_shstrndx(class, ehdr); > + void *shdr; > + char *strtab; > + static int strtable_idx = 1; This can't be static as this will only start at 1 on the first invocation of rproc_minidump(). I think it would be perfectly fine if you simply scan the string list to find the next available slot. > + int idx, ret = 0; No need to initialize ret as the first usage is an assignment. Regards, Bjorn