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    Subject[tip:x86/vdso] x86/vdso, build: Fix cross-compilation from big-endian architectures
    Commit-ID:  add4eed0a2abea3951206f504330ee5daf8c178a
    Gitweb: http://git.kernel.org/tip/add4eed0a2abea3951206f504330ee5daf8c178a
    Author: Andy Lutomirski <luto@amacapital.net>
    AuthorDate: Fri, 30 May 2014 08:48:49 -0700
    Committer: H. Peter Anvin <hpa@linux.intel.com>
    CommitDate: Fri, 30 May 2014 16:58:43 -0700

    x86/vdso, build: Fix cross-compilation from big-endian architectures

    This adds a macro GET(x) to convert x from big-endian to
    little-endian. Hopefully I put it everywhere it needs to go and got
    all the cases needed for everyone's linux/elf.h.

    Signed-off-by: Andy Lutomirski <luto@amacapital.net>
    Link: http://lkml.kernel.org/r/2cf258df123cb24bad63c274c8563c050547d99d.1401464755.git.luto@amacapital.net
    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    ---
    arch/x86/vdso/vdso2c.c | 15 ++++++++++++
    arch/x86/vdso/vdso2c.h | 63 ++++++++++++++++++++++++++++----------------------
    2 files changed, 50 insertions(+), 28 deletions(-)

    diff --git a/arch/x86/vdso/vdso2c.c b/arch/x86/vdso/vdso2c.c
    index fe8bfbf..de19ced 100644
    --- a/arch/x86/vdso/vdso2c.c
    +++ b/arch/x86/vdso/vdso2c.c
    @@ -51,6 +51,21 @@ static void fail(const char *format, ...)
    va_end(ap);
    }

    +/*
    + * Evil macros to do a little-endian read.
    + */
    +#define __GET_TYPE(x, type, bits, ifnot) \
    + __builtin_choose_expr( \
    + __builtin_types_compatible_p(typeof(x), type), \
    + le##bits##toh((x)), ifnot)
    +
    +extern void bad_get(uint64_t);
    +
    +#define GET(x) \
    + __GET_TYPE((x), __u32, 32, __GET_TYPE((x), __u64, 64, \
    + __GET_TYPE((x), __s32, 32, __GET_TYPE((x), __s64, 64, \
    + __GET_TYPE((x), __u16, 16, bad_get(x))))))
    +
    #define NSYMS (sizeof(required_syms) / sizeof(required_syms[0]))

    #define BITS 64
    diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h
    index 26a7c1f..f0475da 100644
    --- a/arch/x86/vdso/vdso2c.h
    +++ b/arch/x86/vdso/vdso2c.h
    @@ -18,25 +18,27 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
    const char *secstrings;
    uint64_t syms[NSYMS] = {};

    - Elf_Phdr *pt = (Elf_Phdr *)(addr + hdr->e_phoff);
    + Elf_Phdr *pt = (Elf_Phdr *)(addr + GET(hdr->e_phoff));

    /* Walk the segment table. */
    - for (i = 0; i < hdr->e_phnum; i++) {
    - if (pt[i].p_type == PT_LOAD) {
    + for (i = 0; i < GET(hdr->e_phnum); i++) {
    + if (GET(pt[i].p_type) == PT_LOAD) {
    if (found_load)
    fail("multiple PT_LOAD segs\n");

    - if (pt[i].p_offset != 0 || pt[i].p_vaddr != 0)
    + if (GET(pt[i].p_offset) != 0 ||
    + GET(pt[i].p_vaddr) != 0)
    fail("PT_LOAD in wrong place\n");

    - if (pt[i].p_memsz != pt[i].p_filesz)
    + if (GET(pt[i].p_memsz) != GET(pt[i].p_filesz))
    fail("cannot handle memsz != filesz\n");

    - load_size = pt[i].p_memsz;
    + load_size = GET(pt[i].p_memsz);
    found_load = 1;
    - } else if (pt[i].p_type == PT_DYNAMIC) {
    - dyn = addr + pt[i].p_offset;
    - dyn_end = addr + pt[i].p_offset + pt[i].p_memsz;
    + } else if (GET(pt[i].p_type) == PT_DYNAMIC) {
    + dyn = addr + GET(pt[i].p_offset);
    + dyn_end = addr + GET(pt[i].p_offset) +
    + GET(pt[i].p_memsz);
    }
    }
    if (!found_load)
    @@ -44,43 +46,48 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
    data_size = (load_size + 4095) / 4096 * 4096;

    /* Walk the dynamic table */
    - for (i = 0; dyn + i < dyn_end && dyn[i].d_tag != DT_NULL; i++) {
    - if (dyn[i].d_tag == DT_REL || dyn[i].d_tag == DT_RELSZ ||
    - dyn[i].d_tag == DT_RELENT || dyn[i].d_tag == DT_TEXTREL)
    + for (i = 0; dyn + i < dyn_end && GET(dyn[i].d_tag) != DT_NULL; i++) {
    + typeof(dyn[i].d_tag) tag = GET(dyn[i].d_tag);
    + if (tag == DT_REL || tag == DT_RELSZ ||
    + tag == DT_RELENT || tag == DT_TEXTREL)
    fail("vdso image contains dynamic relocations\n");
    }

    /* Walk the section table */
    - secstrings_hdr = addr + hdr->e_shoff + hdr->e_shentsize*hdr->e_shstrndx;
    - secstrings = addr + secstrings_hdr->sh_offset;
    - for (i = 0; i < hdr->e_shnum; i++) {
    - Elf_Shdr *sh = addr + hdr->e_shoff + hdr->e_shentsize * i;
    - if (sh->sh_type == SHT_SYMTAB)
    + secstrings_hdr = addr + GET(hdr->e_shoff) +
    + GET(hdr->e_shentsize)*GET(hdr->e_shstrndx);
    + secstrings = addr + GET(secstrings_hdr->sh_offset);
    + for (i = 0; i < GET(hdr->e_shnum); i++) {
    + Elf_Shdr *sh = addr + GET(hdr->e_shoff) +
    + GET(hdr->e_shentsize) * i;
    + if (GET(sh->sh_type) == SHT_SYMTAB)
    symtab_hdr = sh;

    - if (!strcmp(secstrings + sh->sh_name, ".altinstructions"))
    + if (!strcmp(secstrings + GET(sh->sh_name), ".altinstructions"))
    alt_sec = sh;
    }

    if (!symtab_hdr)
    fail("no symbol table\n");

    - strtab_hdr = addr + hdr->e_shoff +
    - hdr->e_shentsize * symtab_hdr->sh_link;
    + strtab_hdr = addr + GET(hdr->e_shoff) +
    + GET(hdr->e_shentsize) * GET(symtab_hdr->sh_link);

    /* Walk the symbol table */
    - for (i = 0; i < symtab_hdr->sh_size / symtab_hdr->sh_entsize; i++) {
    + for (i = 0; i < GET(symtab_hdr->sh_size) / GET(symtab_hdr->sh_entsize);
    + i++) {
    int k;
    - Elf_Sym *sym = addr + symtab_hdr->sh_offset +
    - symtab_hdr->sh_entsize * i;
    - const char *name = addr + strtab_hdr->sh_offset + sym->st_name;
    + Elf_Sym *sym = addr + GET(symtab_hdr->sh_offset) +
    + GET(symtab_hdr->sh_entsize) * i;
    + const char *name = addr + GET(strtab_hdr->sh_offset) +
    + GET(sym->st_name);
    for (k = 0; k < NSYMS; k++) {
    if (!strcmp(name, required_syms[k])) {
    if (syms[k]) {
    fail("duplicate symbol %s\n",
    required_syms[k]);
    }
    - syms[k] = sym->st_value;
    + syms[k] = GET(sym->st_value);
    }
    }
    }
    @@ -106,7 +113,7 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
    hdr->e_shoff = 0;
    hdr->e_shentsize = 0;
    hdr->e_shnum = 0;
    - hdr->e_shstrndx = SHN_UNDEF;
    + hdr->e_shstrndx = htole16(SHN_UNDEF);

    if (!name) {
    fwrite(addr, load_size, 1, outfile);
    @@ -140,9 +147,9 @@ static void GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
    fprintf(outfile, "\t},\n");
    if (alt_sec) {
    fprintf(outfile, "\t.alt = %lu,\n",
    - (unsigned long)alt_sec->sh_offset);
    + (unsigned long)GET(alt_sec->sh_offset));
    fprintf(outfile, "\t.alt_len = %lu,\n",
    - (unsigned long)alt_sec->sh_size);
    + (unsigned long)GET(alt_sec->sh_size));
    }
    for (i = 0; i < NSYMS; i++) {
    if (syms[i])

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