Hello Daisuke, Petr On Thu, May 13, 2010 at 7:55 AM, Daisuke HATAYAMA <d.hatayama@xxxxxxxxxxxxxx> wrote: > Hi. Petr. > > Thank you for your comments. > > I reflected your comments to the previous patch. > Could you check it? > > # What a strange interface, the other two hold the max value while > # e_shnum holds zero in case of overflow. > > I considered one answer to the question based on the difference of > compatibility policy for each object format. > > For core object format, it is better for ordinary tools to understand > as many program headers as possible, even if it is incomplete. On the > other hand, for relocatable object format, it is meaningless if it is > incomplete. This is why e_phnum is set to PN_XNUM(0xffff) and e_shnum > is set to 0, respectively: in the latter case, any ordinary linker > cannot recognize the relocatable object correctly. > > But I don't know why e_shstrndx is set to 0xffff. We could choose it > from the reserved range of section header table indices, i.e. 0 and > [0xff00, ..., 0xffff]. > > At any rate, to see accurately why it's so, we need to look at the > discussion when the ELF extension was specified. I will post it here > if I can find it. > > Thanks > HATAYAMA, Daisuke > --- > linux-2.6.34-rc1 added an ELF core extension, which user-land tools, > such as gdb and binutils, have already supported. Therefore, elf.5 > needs to be modified accordingly. > > You can follow information on the ELF extension via the LKML post: > http://lkml.org/lkml/2010/1/3/103 > > Signed-off-by: Daisuke HATAYAMA <d.hatayama@xxxxxxxxxxxxxx> Daisuke, thanks for your patch. Petr, thanks for the review comments. I made some small language and formatting fixes, but otherwise applied the patch as you gave it. Thanks for supplying this. Cheers, Michael > --- > man5/elf.5 | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- > 1 files changed, 60 insertions(+), 2 deletions(-) > > diff --git a/man5/elf.5 b/man5/elf.5 > index 20ed3d8..e5270e7 100644 > --- a/man5/elf.5 > +++ b/man5/elf.5 > @@ -30,7 +30,7 @@ > .\" 2007-10-11, Mike Frysinger <vapier@xxxxxxxxxx>, various fixes > .\" 2007-12-08, mtk, Converted from mdoc to man macros > .\" > -.TH ELF 5 2007-12-28 "Linux" "Linux Programmer's Manual" > +.TH ELF 5 2010-05-13 "Linux" "Linux Programmer's Manual" > .SH NAME > elf \- format of Executable and Linking Format (ELF) files > .SH SYNOPSIS > @@ -543,6 +543,28 @@ in bytes. > If a file has no program header, > .IR e_phnum > holds the value zero. > +.IP > +If the number of entries in the program header table is larger than or equal to > +.BR PN_XNUM > +(0xffff), this member holds > +.BR PN_XNUM > +(0xffff) and the real number of entries in the program header table is held in > +.IR sh_info > +member of the initial entry in section header table. Otherwise, the > +.IR sh_info > +member of the initial entry contains the value zero. > +.\" .Bl -tag -width "PN_XNUM" > +.RS 12 > +.TP 9 > +.BR PN_XNUM > +This is defined as 0xffff, the largest number > +.IR e_phnum > +can have, specifying where the actual number of program headers is > +assigned. > +.PD > +.RE > +.\" .El > +.IP > .TP > .IR e_shentsize > This member holds a sections header's size in bytes. > @@ -561,6 +583,17 @@ If a file has no section > header table, > .IR e_shnum > holds the value of zero. > +.IP > +If the number of entries in the section header table is larger than or equal to > +.BR SHN_LORESERVE > +(0xff00), > +.IR e_shnum > +holds the value zero and the real number of entries in the section header > +table is held in > +.IR sh_size > +of the initial entry in section header table. Otherwise, the > +.IR sh_size > +of the initial entry in section header table holds the value zero. > .TP > .IR e_shstrndx > This member holds the section header table index of the entry associated > @@ -568,6 +601,17 @@ with the section name string table. > If the file has no section name string > table, this member holds the value > .BR SHN_UNDEF . > +.IP > +If the index of section name string table section is larger than or equal to > +.BR SHN_LORESERVE > +(0xff00), this member holds > +.BR SHN_XINDEX > +(0xffff) and the real index of the section name string table section > +is held in the > +.IR sh_link > +member of the initial entry in section header table. Otherwise, the > +.IR sh_link > +member of the initial entry in section header table contains the value zero. > .RS 12 > .\" .Bl -tag -width "SHN_LORESERVE" > .TP 14 > @@ -841,7 +885,10 @@ holds the size in bytes of each entry. > .PP > A section header table index is a subscript into this array. > Some section > -header table indices are reserved. > +header table indices are reserved: > +the initial entry and the indices between SHN_LORESERVE and SHN_HIRESERVE. > +The initial entry is used in ELF extensions for e_phnum, e_shnum and e_strndx; > +in other cases, each field in the initial entry is set to zero. > An object file does not have sections for > these special indices: > .\" .Bl -tag -width "SHN_LORESERVE" > @@ -1851,6 +1898,10 @@ This is automatically populated by the linker. > ELF first appeared in > System V. > The ELF format is an adopted standard. > +.PP > +The extensions for e_phnum, e_shnum and e_strndx respectively are > +Linux extensions. Sun, BSD and AMD64 also support them, whose > +specifications are listed in SEE ALSO. > .\" .SH AUTHORS > .\" The original version of this manual page was written by > .\" .An Jeroen Ruigrok van der Werven > @@ -1876,3 +1927,10 @@ Santa Cruz Operation, > Unix System Laboratories, > "Object Files", > .IR "Executable and Linking Format (ELF)" . > +.PP > +Sun microsystems, > +.IR "Linker and Libraries Guide" . > +.PP > +AMD64 ABI Draft, > +.IR "System V Application Binary Interface AMD64 Architecture Processor Supplement" . > +.PP > -- > 1.6.5.1 > -- > To unsubscribe from this list: send the line "unsubscribe linux-man" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface" http://blog.man7.org/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
