entry/vdso/vdso2c.c

1 // SPDX-License-Identifier: GPL-2.0-only
3  * vdso2c - A vdso image preparation tool
7  * to fully strip the input in here, but, for reasons described below,
9  * equivalent to dropping all non-allocatable sections, but it's
16  * The Go runtime had a couple of bugs: it would read the section
18  * shouldn't have looked at the section table at all) and, if there
20  * uninitialized value for the number of symbols.  An empty DYNSYM
22  * keep full performance for old Go programs).  This hack is only
23  * needed on x86_64.
25  * The bug was introduced on 2012-08-31 by:
26  * https://code.google.com/p/go/source/detail?r=56ea40aac72b
27  * and was fixed on 2014-06-13 by:
28  * https://code.google.com/p/go/source/detail?r=fc1cd5e12595
30  * Binutils has issues debugging the vDSO: it reads the section table to
31  * find SHT_NOTE; it won't look at PT_NOTE for the in-memory vDSO, which
32  * would break build-id if we removed the section table.  Binutils
40  * just write a mostly complete one.  We omit non-dynamic symbols,
44  * the 64-bit vdso, since build-id only works in kernel RPMs, and
46  * binutils in sync.  build-id has never worked for home-built kernel
122  * Evil macros for little-endian reads and writes
169 static void go(void *raw_addr, size_t raw_len,  in go()  function
175 	if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {  in go()
178 	} else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {  in go()
191 	if (fd == -1)  in map_input()
195 	if (tmp_len == (off_t)-1)  in map_input()
220 	 * Figure out the struct name.  If we're writing to a .so file,  in main()
225 	if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) {  in main()
235 			if (*tmp == '-')  in main()
247 	go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name);  in main()