Re: [PATCH 1/2 v5] kdump: add the vmcoreinfo documentation
在 2019年01月07日 15:55, Hatayama, Daisuke 写道: > Hi, > >> -Original Message- >> From: linux-kernel-ow...@vger.kernel.org >> [mailto:linux-kernel-ow...@vger.kernel.org] On Behalf Of Lianbo Jiang >> Sent: Monday, January 7, 2019 10:48 AM >> To: linux-kernel@vger.kernel.org >> Cc: ke...@lists.infradead.org; t...@linutronix.de; mi...@redhat.com; >> b...@alien8.de; x...@kernel.org; a...@linux-foundation.org; b...@redhat.com; >> dyo...@redhat.com; linux-...@vger.kernel.org; k-ha...@ab.jp.nec.com; >> ander...@redhat.com >> Subject: [PATCH 1/2 v5] kdump: add the vmcoreinfo documentation >> >> This document lists some variables that export to vmcoreinfo, and briefly >> describles what these variables indicate. It should be instructive for >> many people who do not know the vmcoreinfo, and it also normalizes the > > I agree to this part, but > >> exported variables as a convention between kernel and use-space. > > I don't agree to this part. > > The meaning of each symbol is decided by each feature in the kernel, > not by vmcoreinfo. I suspect anyone mistakenly understand this document is > ABI enforcing each symbol works as described. We can change symbols and > their meaning regardless of this document. > > Oh, I found this topic has already been discussed at v3, and > you removed "ABI" in the patch description at v4. > > But it seems still confusing to me. > I think the explicit description saying that this is for user-land tools, > they treats each symbol as described, > and the document never affect implementation of each kernel components, > is necessary in e.g. "Purpose of this document" section? > Thanks for your advice. If this part could make the document become a rope tied around our necks, i would like to remove this part from the patch log in next post. Regards, Lianbo >> >> Suggested-by: Borislav Petkov >> Signed-off-by: Lianbo Jiang >> --- >> Documentation/kdump/vmcoreinfo.txt | 500 + >> 1 file changed, 500 insertions(+) >> create mode 100644 Documentation/kdump/vmcoreinfo.txt >> >> diff --git a/Documentation/kdump/vmcoreinfo.txt >> b/Documentation/kdump/vmcoreinfo.txt >> new file mode 100644 >> index ..8e444586b87b >> --- /dev/null >> +++ b/Documentation/kdump/vmcoreinfo.txt >> @@ -0,0 +1,500 @@ >> + >> +VMCOREINFO >> + >> + >> +=== >> +What is the VMCOREINFO? >> +=== >> + >> +VMCOREINFO is a special ELF note section. It contains various >> +information from the kernel like structure size, page size, symbol >> +values, field offsets, etc. These data are packed into an ELF note >> +section and used by user-space tools like crash and makedumpfile to >> +analyze a kernel's memory layout. >> + >> + >> +Common variables >> + >> + >> +init_uts_ns.name.release >> + >> + >> +The version of the Linux kernel. Used to find the corresponding source >> +code from which the kernel has been built. >> + >> +PAGE_SIZE >> +- >> + >> +The size of a page. It is the smallest unit of data for memory >> +management in kernel. It is usually 4096 bytes and a page is aligned >> +on 4096 bytes. Used for computing page addresses. >> + >> +init_uts_ns >> +--- >> + >> +This is the UTS namespace, which is used to isolate two specific >> +elements of the system that relate to the uname(2) system call. The UTS >> +namespace is named after the data structure used to store information >> +returned by the uname(2) system call. >> + >> +User-space tools can get the kernel name, host name, kernel release >> +number, kernel version, architecture name and OS type from it. >> + >> +node_online_map >> +--- >> + >> +An array node_states[N_ONLINE] which represents the set of online node >> +in a system, one bit position per node number. Used to keep track of >> +which nodes are in the system and online. >> + >> +swapper_pg_dir >> +- >> + >> +The global page directory pointer of the kernel. Used to translate >> +virtual to physical addresses. >> + >> +_stext >> +-- >> + >> +Defines the beginning of the text section. In general, _stext indicates >> +the kernel start address. Used to convert a virtual address from the >> +direct kernel map to a physical address. >> + >> +vmap_area_list >> +-- >> + >> +Stores the virtual area list. makedumpfile can get the vmalloc start >> +value from this variable. This value is necessary for vmalloc translation. >> + >> +mem_map >> +--- >> + >> +Physical addresses are translated to struct pages by treating them as >> +an index into the mem_map array. Right-shifting a physical address >> +PAGE_SHIFT bits converts it into a page frame number which is an index >> +into that mem_map array. >> + >> +Used to map an address to the corresponding struct page.
RE: [PATCH 1/2 v5] kdump: add the vmcoreinfo documentation
Hi, > -Original Message- > From: linux-kernel-ow...@vger.kernel.org > [mailto:linux-kernel-ow...@vger.kernel.org] On Behalf Of Lianbo Jiang > Sent: Monday, January 7, 2019 10:48 AM > To: linux-kernel@vger.kernel.org > Cc: ke...@lists.infradead.org; t...@linutronix.de; mi...@redhat.com; > b...@alien8.de; x...@kernel.org; a...@linux-foundation.org; b...@redhat.com; > dyo...@redhat.com; linux-...@vger.kernel.org; k-ha...@ab.jp.nec.com; > ander...@redhat.com > Subject: [PATCH 1/2 v5] kdump: add the vmcoreinfo documentation > > This document lists some variables that export to vmcoreinfo, and briefly > describles what these variables indicate. It should be instructive for > many people who do not know the vmcoreinfo, and it also normalizes the I agree to this part, but > exported variables as a convention between kernel and use-space. I don't agree to this part. The meaning of each symbol is decided by each feature in the kernel, not by vmcoreinfo. I suspect anyone mistakenly understand this document is ABI enforcing each symbol works as described. We can change symbols and their meaning regardless of this document. Oh, I found this topic has already been discussed at v3, and you removed "ABI" in the patch description at v4. But it seems still confusing to me. I think the explicit description saying that this is for user-land tools, they treats each symbol as described, and the document never affect implementation of each kernel components, is necessary in e.g. "Purpose of this document" section? > > Suggested-by: Borislav Petkov > Signed-off-by: Lianbo Jiang > --- > Documentation/kdump/vmcoreinfo.txt | 500 + > 1 file changed, 500 insertions(+) > create mode 100644 Documentation/kdump/vmcoreinfo.txt > > diff --git a/Documentation/kdump/vmcoreinfo.txt > b/Documentation/kdump/vmcoreinfo.txt > new file mode 100644 > index ..8e444586b87b > --- /dev/null > +++ b/Documentation/kdump/vmcoreinfo.txt > @@ -0,0 +1,500 @@ > + > + VMCOREINFO > + > + > +=== > +What is the VMCOREINFO? > +=== > + > +VMCOREINFO is a special ELF note section. It contains various > +information from the kernel like structure size, page size, symbol > +values, field offsets, etc. These data are packed into an ELF note > +section and used by user-space tools like crash and makedumpfile to > +analyze a kernel's memory layout. > + > + > +Common variables > + > + > +init_uts_ns.name.release > + > + > +The version of the Linux kernel. Used to find the corresponding source > +code from which the kernel has been built. > + > +PAGE_SIZE > +- > + > +The size of a page. It is the smallest unit of data for memory > +management in kernel. It is usually 4096 bytes and a page is aligned > +on 4096 bytes. Used for computing page addresses. > + > +init_uts_ns > +--- > + > +This is the UTS namespace, which is used to isolate two specific > +elements of the system that relate to the uname(2) system call. The UTS > +namespace is named after the data structure used to store information > +returned by the uname(2) system call. > + > +User-space tools can get the kernel name, host name, kernel release > +number, kernel version, architecture name and OS type from it. > + > +node_online_map > +--- > + > +An array node_states[N_ONLINE] which represents the set of online node > +in a system, one bit position per node number. Used to keep track of > +which nodes are in the system and online. > + > +swapper_pg_dir > +- > + > +The global page directory pointer of the kernel. Used to translate > +virtual to physical addresses. > + > +_stext > +-- > + > +Defines the beginning of the text section. In general, _stext indicates > +the kernel start address. Used to convert a virtual address from the > +direct kernel map to a physical address. > + > +vmap_area_list > +-- > + > +Stores the virtual area list. makedumpfile can get the vmalloc start > +value from this variable. This value is necessary for vmalloc translation. > + > +mem_map > +--- > + > +Physical addresses are translated to struct pages by treating them as > +an index into the mem_map array. Right-shifting a physical address > +PAGE_SHIFT bits converts it into a page frame number which is an index > +into that mem_map array. > + > +Used to map an address to the corresponding struct page. > + > +contig_page_data > + > + > +Makedumpfile can get the pglist_data structure from this symbol, which > +is used to describe the memory layout. > + > +User-space tools use this to exclude free pages when dumping memory. > + > +mem_section|(mem_section, NR_SECTION_ROOTS)|(mem_section, section_mem_map) >
