[PATCH] scripts: Make sortextable handle relocations.

From: David Daney
Date: Fri Apr 20 2012 - 18:41:28 EST

From: David Daney <david.daney@xxxxxxxxxx>

If there are relocations on the __ex_table section, they must be fixed
up after the table is sorted.

Also use the unaligned safe accessors from tools/{be,le}_byteshift.h

Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
---

This should address HPA's concerns about the i386 relocations. The
i386 kernel still boots after the sort, but I don't know how to test
the relocations, but they sure do look nice! My MIPS64 kernels still
boot too, so that is also good.

scripts/Makefile | 2 +
scripts/sortextable.c | 123 +++++++++++++++++++++++--------------------
scripts/sortextable.h | 138 +++++++++++++++++++++++++++++++++++++++----------
3 files changed, 178 insertions(+), 85 deletions(-)

diff --git a/scripts/Makefile b/scripts/Makefile
index 43e19b9..9eace52 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -15,6 +15,8 @@ hostprogs-$(CONFIG_IKCONFIG) += bin2c
hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount
hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable

+HOSTCFLAGS_sortextable.o = -I$(srctree)/tools/include
+
always := $(hostprogs-y) $(hostprogs-m)

# The following hostprogs-y programs are only build on demand
diff --git a/scripts/sortextable.c b/scripts/sortextable.c
index 6546785..d876045 100644
--- a/scripts/sortextable.c
+++ b/scripts/sortextable.c
@@ -1,7 +1,7 @@
/*
* sortextable.c: Sort the kernel's exception table
*
- * Copyright 2011 Cavium, Inc.
+ * Copyright 2011 - 2012 Cavium, Inc.
*
* Based on code taken from recortmcount.c which is:
*
@@ -28,6 +28,9 @@
#include <string.h>
#include <unistd.h>

+#include <tools/be_byteshift.h>
+#include <tools/le_byteshift.h>
+
static int fd_map; /* File descriptor for file being modified. */
static int mmap_failed; /* Boolean flag. */
static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
@@ -94,52 +97,62 @@ static void *mmap_file(char const *fname)
return addr;
}

-/* w8rev, w8nat, ...: Handle endianness. */
-
-static uint64_t w8rev(uint64_t const x)
+static uint64_t r8be(const uint64_t *x)
{
- return ((0xff & (x >> (0 * 8))) << (7 * 8))
- | ((0xff & (x >> (1 * 8))) << (6 * 8))
- | ((0xff & (x >> (2 * 8))) << (5 * 8))
- | ((0xff & (x >> (3 * 8))) << (4 * 8))
- | ((0xff & (x >> (4 * 8))) << (3 * 8))
- | ((0xff & (x >> (5 * 8))) << (2 * 8))
- | ((0xff & (x >> (6 * 8))) << (1 * 8))
- | ((0xff & (x >> (7 * 8))) << (0 * 8));
+ return get_unaligned_be64(x);
}
-
-static uint32_t w4rev(uint32_t const x)
+static uint32_t rbe(const uint32_t *x)
{
- return ((0xff & (x >> (0 * 8))) << (3 * 8))
- | ((0xff & (x >> (1 * 8))) << (2 * 8))
- | ((0xff & (x >> (2 * 8))) << (1 * 8))
- | ((0xff & (x >> (3 * 8))) << (0 * 8));
+ return get_unaligned_be32(x);
}
-
-static uint32_t w2rev(uint16_t const x)
+static uint16_t r2be(const uint16_t *x)
{
- return ((0xff & (x >> (0 * 8))) << (1 * 8))
- | ((0xff & (x >> (1 * 8))) << (0 * 8));
+ return get_unaligned_be16(x);
}
-
-static uint64_t w8nat(uint64_t const x)
+static uint64_t r8le(const uint64_t *x)
{
- return x;
+ return get_unaligned_le64(x);
}
-
-static uint32_t w4nat(uint32_t const x)
+static uint32_t rle(const uint32_t *x)
+{
+ return get_unaligned_le32(x);
+}
+static uint16_t r2le(const uint16_t *x)
{
- return x;
+ return get_unaligned_le16(x);
}

-static uint32_t w2nat(uint16_t const x)
+static void w8be(uint64_t val, uint64_t *x)
+{
+ put_unaligned_be64(val, x);
+}
+static void wbe(uint32_t val, uint32_t *x)
{
- return x;
+ put_unaligned_be32(val, x);
+}
+static void w2be(uint16_t val, uint16_t *x)
+{
+ put_unaligned_be16(val, x);
+}
+static void w8le(uint64_t val, uint64_t *x)
+{
+ put_unaligned_le64(val, x);
+}
+static void wle(uint32_t val, uint32_t *x)
+{
+ put_unaligned_le32(val, x);
+}
+static void w2le(uint16_t val, uint16_t *x)
+{
+ put_unaligned_le16(val, x);
}

-static uint64_t (*w8)(uint64_t);
-static uint32_t (*w)(uint32_t);
-static uint32_t (*w2)(uint16_t);
+static uint64_t (*r8)(const uint64_t *);
+static uint32_t (*r)(const uint32_t *);
+static uint16_t (*r2)(const uint16_t *);
+static void (*w8)(uint64_t, uint64_t *);
+static void (*w)(uint32_t, uint32_t *);
+static void (*w2)(uint16_t, uint16_t *);


/* 32 bit and 64 bit are very similar */
@@ -151,47 +164,43 @@ static uint32_t (*w2)(uint16_t);
static void
do_file(char const *const fname)
{
- Elf32_Ehdr *const ehdr = mmap_file(fname);
+ Elf32_Ehdr *ehdr = mmap_file(fname);

ehdr_curr = ehdr;
- w = w4nat;
- w2 = w2nat;
- w8 = w8nat;
switch (ehdr->e_ident[EI_DATA]) {
- static unsigned int const endian = 1;
default:
fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
ehdr->e_ident[EI_DATA], fname);
fail_file();
break;
case ELFDATA2LSB:
- if (*(unsigned char const *)&endian != 1) {
- /* main() is big endian, file.o is little endian. */
- w = w4rev;
- w2 = w2rev;
- w8 = w8rev;
- }
+ r = rle;
+ r2 = r2le;
+ r8 = r8le;
+ w = wle;
+ w2 = w2le;
+ w8 = w8le;
break;
case ELFDATA2MSB:
- if (*(unsigned char const *)&endian != 0) {
- /* main() is little endian, file.o is big endian. */
- w = w4rev;
- w2 = w2rev;
- w8 = w8rev;
- }
+ r = rbe;
+ r2 = r2be;
+ r8 = r8be;
+ w = wbe;
+ w2 = w2be;
+ w8 = w8be;
break;
} /* end switch */
if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
- || w2(ehdr->e_type) != ET_EXEC
+ || r2(&ehdr->e_type) != ET_EXEC
|| ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
fprintf(stderr, "unrecognized ET_EXEC file %s\n", fname);
fail_file();
}

- switch (w2(ehdr->e_machine)) {
+ switch (r2(&ehdr->e_machine)) {
default:
fprintf(stderr, "unrecognized e_machine %d %s\n",
- w2(ehdr->e_machine), fname);
+ r2(&ehdr->e_machine), fname);
fail_file();
break;
case EM_386:
@@ -207,8 +216,8 @@ do_file(char const *const fname)
fail_file();
break;
case ELFCLASS32:
- if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
- || w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
+ if (r2(&ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
+ || r2(&ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
fprintf(stderr,
"unrecognized ET_EXEC file: %s\n", fname);
fail_file();
@@ -217,8 +226,8 @@ do_file(char const *const fname)
break;
case ELFCLASS64: {
Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
- if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
- || w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
+ if (r2(&ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
+ || r2(&ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
fprintf(stderr,
"unrecognized ET_EXEC file: %s\n", fname);
fail_file();
diff --git a/scripts/sortextable.h b/scripts/sortextable.h
index bb6aaf1..27b1439 100644
--- a/scripts/sortextable.h
+++ b/scripts/sortextable.h
@@ -1,7 +1,7 @@
/*
* sortextable.h
*
- * Copyright 2011 Cavium, Inc.
+ * Copyright 2011 - 2012 Cavium, Inc.
*
* Some of this code was taken out of recordmcount.h written by:
*
@@ -14,7 +14,10 @@

#undef extable_ent_size
#undef compare_extable
+#undef work_struct
+#undef relocs_struct
#undef do_func
+#undef find_reloc
#undef Elf_Addr
#undef Elf_Ehdr
#undef Elf_Shdr
@@ -30,12 +33,16 @@
#undef fn_ELF_R_SYM
#undef fn_ELF_R_INFO
#undef uint_t
+#undef _r
#undef _w

#ifdef SORTEXTABLE_64
# define extable_ent_size 16
# define compare_extable compare_extable_64
+# define work_struct work_struct_64
+# define relocs_struct relocs_struc_64
# define do_func do64
+# define find_reloc find_reloc64
# define Elf_Addr Elf64_Addr
# define Elf_Ehdr Elf64_Ehdr
# define Elf_Shdr Elf64_Shdr
@@ -51,11 +58,15 @@
# define fn_ELF_R_SYM fn_ELF64_R_SYM
# define fn_ELF_R_INFO fn_ELF64_R_INFO
# define uint_t uint64_t
+# define _r r8
# define _w w8
#else
# define extable_ent_size 8
# define compare_extable compare_extable_32
+# define work_struct work_struct_32
+# define relocs_struct relocs_struc_32
# define do_func do32
+# define find_reloc find_reloc32
# define Elf_Addr Elf32_Addr
# define Elf_Ehdr Elf32_Ehdr
# define Elf_Shdr Elf32_Shdr
@@ -71,23 +82,48 @@
# define fn_ELF_R_SYM fn_ELF32_R_SYM
# define fn_ELF_R_INFO fn_ELF32_R_INFO
# define uint_t uint32_t
+# define _r r
# define _w w
#endif

+struct work_struct {
+ /* Literal copy of the entry. */
+ char ent[extable_ent_size];
+ /* Original position of the entry. */
+ int ex_table_idx;
+ /* Position of the relocations. */
+ int rel_idx0;
+ int rel_idx1;
+};
+
+struct relocs_struct {
+ Elf_Rel *relocs;
+ int size;
+};
+
static int compare_extable(const void *a, const void *b)
{
- const uint_t *aa = a;
- const uint_t *bb = b;
+ const struct work_struct *aa = a;
+ const struct work_struct *bb = b;

- if (_w(*aa) < _w(*bb))
+ if (_r((Elf_Addr *)(aa->ent)) < _r((Elf_Addr *)(bb->ent)))
return -1;
- if (_w(*aa) > _w(*bb))
+ if (_r((Elf_Addr *)(aa->ent)) > _r((Elf_Addr *)(bb->ent)))
return 1;
return 0;
}
+static int find_reloc(struct relocs_struct *relocs, Elf_Addr target)
+{
+ int i;
+
+ for (i = 0; i < relocs->size; i++)
+ if (_r(&relocs->relocs[i].r_offset) == target)
+ return i;
+ return -1;
+}

static void
-do_func(Elf_Ehdr *const ehdr, char const *const fname)
+do_func(Elf_Ehdr *ehdr, char const *const fname)
{
Elf_Shdr *shdr;
Elf_Shdr *shstrtab_sec;
@@ -100,16 +136,29 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname)
uint32_t *sort_done_location;
const char *secstrtab;
const char *strtab;
+ struct work_struct *work_array;
+ struct relocs_struct relocs = {NULL, 0};
+ char *extab_image;
+ Elf_Addr extab_virt;
+ int extab_index = 0;
+ int num_entries;
int i;
int idx;

- shdr = (Elf_Shdr *)((void *)ehdr + _w(ehdr->e_shoff));
- shstrtab_sec = shdr + w2(ehdr->e_shstrndx);
- secstrtab = (const char *)ehdr + _w(shstrtab_sec->sh_offset);
- for (i = 0; i < w2(ehdr->e_shnum); i++) {
- idx = w(shdr[i].sh_name);
- if (strcmp(secstrtab + idx, "__ex_table") == 0)
+ shdr = (Elf_Shdr *)((void *)ehdr + _r(&ehdr->e_shoff));
+ shstrtab_sec = shdr + r2(&ehdr->e_shstrndx);
+ secstrtab = (const char *)ehdr + _r(&shstrtab_sec->sh_offset);
+ for (i = 0; i < r2(&ehdr->e_shnum); i++) {
+ idx = r(&shdr[i].sh_name);
+ if (strcmp(secstrtab + idx, "__ex_table") == 0) {
extab_sec = shdr + i;
+ extab_index = i;
+ }
+ if (r(&shdr[i].sh_type) == SHT_REL &&
+ r(&shdr[i].sh_info) == extab_index) {
+ relocs.relocs = (void *)ehdr + _r(&shdr[i].sh_offset);
+ relocs.size = _r(&shdr[i].sh_size) / sizeof(Elf_Rel);
+ }
if (strcmp(secstrtab + idx, ".symtab") == 0)
symtab_sec = shdr + i;
if (strcmp(secstrtab + idx, ".strtab") == 0)
@@ -127,21 +176,56 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname)
fprintf(stderr, "no __ex_table in file: %s\n", fname);
fail_file();
}
- strtab = (const char *)ehdr + _w(strtab_sec->sh_offset);
+ strtab = (const char *)ehdr + _r(&strtab_sec->sh_offset);

- /* Sort the table in place */
- qsort((void *)ehdr + _w(extab_sec->sh_offset),
- (_w(extab_sec->sh_size) / extable_ent_size),
- extable_ent_size, compare_extable);
+ num_entries = _r(&extab_sec->sh_size) / extable_ent_size;
+ work_array = calloc(num_entries, sizeof(*work_array));
+ if (work_array == NULL) {
+ fprintf(stderr, "Failed to allocate work_array\n");
+ fail_file();
+ }
+ extab_image = (void *)ehdr + _r(&extab_sec->sh_offset);
+ extab_virt = _r(&extab_sec->sh_addr);
+
+
+ /* Copy into the work_array. */
+ for (i = 0; i < num_entries; i++) {
+ memcpy(work_array[i].ent,
+ extab_image + (i * extable_ent_size), extable_ent_size);
+ work_array[i].ex_table_idx = i;
+ work_array[i].rel_idx0 = find_reloc(&relocs,
+ extab_virt + (i * extable_ent_size));
+ work_array[i].rel_idx1 = find_reloc(&relocs,
+ extab_virt + (i * extable_ent_size) + sizeof(Elf_Addr));
+ }
+
+ /* Sort the work_array */
+ qsort(work_array, num_entries, sizeof(*work_array), compare_extable);
+
+ /* Copy it back out. */
+ for (i = 0; i < num_entries; i++) {
+ memcpy(extab_image + (i * extable_ent_size),
+ work_array[i].ent, extable_ent_size);
+ /* Patch up the relocs */
+ if (work_array[i].rel_idx0 >= 0) {
+ Elf_Addr t = extab_virt + (i * extable_ent_size);
+ _w(t, &relocs.relocs[work_array[i].rel_idx0].r_offset);
+ }
+ if (work_array[i].rel_idx1 >= 0) {
+ Elf_Addr t = extab_virt + (i * extable_ent_size) + sizeof(Elf_Addr);
+ _w(t, &relocs.relocs[work_array[i].rel_idx1].r_offset);
+ }
+
+ }

/* find main_extable_sort_needed */
sort_needed_sym = NULL;
- for (i = 0; i < _w(symtab_sec->sh_size) / sizeof(Elf_Sym); i++) {
- sym = (void *)ehdr + _w(symtab_sec->sh_offset);
+ for (i = 0; i < _r(&symtab_sec->sh_size) / sizeof(Elf_Sym); i++) {
+ sym = (void *)ehdr + _r(&symtab_sec->sh_offset);
sym += i;
if (ELF_ST_TYPE(sym->st_info) != STT_OBJECT)
continue;
- idx = w(sym->st_name);
+ idx = r(&sym->st_name);
if (strcmp(strtab + idx, "main_extable_sort_needed") == 0) {
sort_needed_sym = sym;
break;
@@ -153,16 +237,14 @@ do_func(Elf_Ehdr *const ehdr, char const *const fname)
fname);
fail_file();
}
- sort_needed_sec = &shdr[w2(sort_needed_sym->st_shndx)];
+ sort_needed_sec = &shdr[r2(&sort_needed_sym->st_shndx)];
sort_done_location = (void *)ehdr +
- _w(sort_needed_sec->sh_offset) +
- _w(sort_needed_sym->st_value) -
- _w(sort_needed_sec->sh_addr);
+ _r(&sort_needed_sec->sh_offset) +
+ _r(&sort_needed_sym->st_value) -
+ _r(&sort_needed_sec->sh_addr);

printf("sort done marker at %lx\n",
- (unsigned long) (_w(sort_needed_sec->sh_offset) +
- _w(sort_needed_sym->st_value) -
- _w(sort_needed_sec->sh_addr)));
+ (unsigned long)((char *)sort_done_location - (char *)ehdr));
/* We sorted it, clear the flag. */
- *sort_done_location = 0;
+ w(0, sort_done_location);
}
--
1.7.2.3

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