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>

2 files changed, 50 insertions, 28 deletions

diff --git a/arch/x86/vdso/vdso2c.c b/arch/x86/vdso/vdso2c.c
index fe8bfbf62612..de19ced6c87d 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 26a7c1fa7452..f0475dad2286 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])