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[PATCH] Handle unsorted section header table
Hi,
Consider a hello world, with .gdb_index added by the gold linker. When
running dwz, we run into this error:
...
$ gcc hello.c -g -fuse-ld=gold -Wl,--gdb-index
$ dwz a.out
dwz: Section offsets in a.out not monotonically increasing
...
Inspecting the section offsets around .gdb_index:
...
$ readelf -S a.out | grep '[[]' | egrep -C1 'Offset|\.gdb_index'
[Nr] Name Type Address Offset
[ 0] NULL 0000000000000000 00000000
--
[31] .debug_str PROGBITS 0000000000000000 00001b2f
[32] .gdb_index PROGBITS 0000000000000000 000034b0
[33] .debug_ranges PROGBITS 0000000000000000 000021f0
...
indeed shows that the offsets are not monotonically increasing.
Handle unsorted section header table in write_dso by:
- rewriting loop (*) in sh_offset updating code to handle unsorted section
header table
- rewriting sh_offset comparisons using before/after relation
arrays after_sht and sorted_section_pos, to make the sh_offset updating
code more robust.
- rewriting the sh_offset alignment updating loops to loop in
sh_offset order.
(*) Specifically, this one:
...
for (j = dso->ehdr.e_shstrndx + 1; j < dso->ehdr.e_shnum; ++j)
dso->shdr[j].sh_offset += len;
...
OK for trunk?
Thanks,
- Tom
Handle unsorted section header table
2019-03-12 Tom de Vries <tdevries@suse.de>
PR dwz/24249
* dwz.c (compare_section_numbers, sort_dso): New function.
(write_dso): Handle unsorted section header table.
* Makefile (TEST_EXECS): Add hello-gold-gdb-index.
(hello-gold-gdb-index): New target.
* testsuite/dwz.tests/dwz-tests.exp: Require hello-gold-gdb-index for
gold-gdb-index.sh.
* testsuite/dwz.tests/gold-gdb-index.sh: New test.
---
Makefile | 5 +-
dwz.c | 144 +++++++++++++++++++++++++++++++---
testsuite/dwz.tests/dwz-tests.exp | 22 +++++-
testsuite/dwz.tests/gold-gdb-index.sh | 13 +++
4 files changed, 169 insertions(+), 15 deletions(-)
diff --git a/Makefile b/Makefile
index b318fd7..643ce0a 100644
--- a/Makefile
+++ b/Makefile
@@ -17,11 +17,14 @@ clean:
PWD:=$(shell pwd -P)
-TEST_EXECS = hello
+TEST_EXECS = hello hello-gold-gdb-index
hello:
$(CC) hello.c -o $@ -g
+hello-gold-gdb-index:
+ $(CC) hello.c -g -fuse-ld=gold -Wl,--gdb-index -o $@ || touch $@
+
check: dwz $(TEST_EXECS)
mkdir -p testsuite-bin
cd testsuite-bin; ln -sf $(PWD)/dwz .
diff --git a/dwz.c b/dwz.c
index 476807a..45d5041 100644
--- a/dwz.c
+++ b/dwz.c
@@ -10041,6 +10041,99 @@ error_out:
return NULL;
}
+/* Array of section numbers sorted by sh_offset. So, this holds:
+ (sorted_section_numbers[i].sh_offset
+ < sorted_section_numbers[i + 1].sh_offset).
+ It can be used to iterate over sections in sh_offset order:
+ for (i = 1, j = sorted_section_numbers[i];
+ i < n;
+ ++i, j = sorted_section_numbers[i]). */
+static unsigned int *sorted_section_numbers;
+
+/* Array of positions of section numbers in sorted_section_numbers array.
+ So, this holds:
+ (sorted_section_pos[sorted_section_numbers[i]] == i).
+ It can be used to safely test before/after relationship in terms of sh_offset
+ in loops where sh_offset is modified, replacing:
+ if (dso->shdr[i].sh_offset < dso->shdr[i].sh_offset)
+ with:
+ if (sorted_section_pos[i] < sorted_section_pos[j]). */
+static unsigned int *sorted_section_pos;
+
+/* Array for use in compare_section_numbers. Could be passed in as arg when
+ using qsort_r instead. */
+static GElf_Shdr *section_headers;
+
+static int
+compare_section_numbers (const void *p1, const void *p2)
+{
+ const int i1 = *(const int *)p1;
+ const int i2 = *(const int *)p2;
+
+ /* Keep element 0 at 0. */
+ if (i1 == 0 || i2 == 0)
+ {
+ if (i1 == i2)
+ return 0;
+ if (i1 == 0)
+ return -1;
+ if (i2 == 0)
+ return 1;
+ }
+
+ if (section_headers[i1].sh_offset
+ < section_headers[i2].sh_offset)
+ return -1;
+
+ if (section_headers[i1].sh_offset
+ > section_headers[i2].sh_offset)
+ return 1;
+
+ /* In case sh_offset is the same, keep the original relative order. */
+ if (i1 < i2)
+ return -1;
+ if (i1 > i2)
+ return 1;
+
+ return 0;
+}
+
+static int
+sort_dso (DSO *dso)
+{
+ unsigned int i;
+
+ sorted_section_numbers
+ = (unsigned int *)malloc (dso->ehdr.e_shnum * sizeof (unsigned int));
+ if (sorted_section_numbers == NULL)
+ {
+ error (0, ENOMEM, "Could not sort DSO");
+ return 1;
+ }
+
+ sorted_section_pos
+ = (unsigned int *)malloc (dso->ehdr.e_shnum * sizeof (unsigned int));
+ if (sorted_section_pos == NULL)
+ {
+ error (0, ENOMEM, "Could not sort DSO");
+ return 1;
+ }
+
+ for (i = 0; i < dso->ehdr.e_shnum; ++i)
+ sorted_section_numbers[i] = i;
+
+ section_headers = dso->shdr;
+ qsort (sorted_section_numbers, dso->ehdr.e_shnum,
+ sizeof (sorted_section_numbers[0]), compare_section_numbers);
+ section_headers = NULL;
+ assert (sorted_section_numbers[0] == 0);
+
+ for (i = 0; i < dso->ehdr.e_shnum; ++i)
+ sorted_section_pos[sorted_section_numbers[i]] = i;
+
+ return 0;
+}
+
/* Store new ELF into FILE. debug_sections array contains
new_data/new_size pairs where needed. */
static int
@@ -10056,15 +10149,33 @@ write_dso (DSO *dso, const char *file, struct stat *st)
GElf_Word shstrtabadd = 0;
char *shstrtab = NULL;
bool remove_sections[SECTION_COUNT];
+ bool after_sht[dso->ehdr.e_shnum];
+
+ if (sort_dso (dso))
+ return 1;
memset (remove_sections, '\0', sizeof (remove_sections));
+ memset (after_sht, '\0', sizeof (after_sht));
+
ehdr = dso->ehdr;
if (multi_ehdr.e_ident[0] == '\0')
multi_ehdr = ehdr;
+ /* The after_sht array records the position of the section header table
+ relative to the sections. It can be used to safely test before/after
+ relationship in terms of sh_offset in loops where sh_offset is modified,
+ replacing:
+ dso->shdr[i].sh_offset > dso->ehdr.e_shoff
+ with
+ after_sht[i]. */
+ for (i = 1; i < dso->ehdr.e_shnum; ++i)
+ if (dso->shdr[i].sh_offset > dso->ehdr.e_shoff)
+ after_sht[i] = true;
+
for (i = 0; debug_sections[i].name; i++)
if (debug_sections[i].new_size != debug_sections[i].size)
{
+ unsigned int off_index;
if (debug_sections[i].size == 0
&& debug_sections[i].sec == 0)
{
@@ -10080,7 +10191,7 @@ write_dso (DSO *dso, const char *file, struct stat *st)
min_shoff = ehdr.e_shoff;
for (j = 1; j < dso->ehdr.e_shnum; ++j)
{
- if (dso->shdr[j].sh_offset > ehdr.e_shoff)
+ if (after_sht[j])
dso->shdr[j].sh_offset += ehdr.e_shentsize;
if (dso->shdr[j].sh_link > (unsigned int) addsec)
dso->shdr[j].sh_link++;
@@ -10097,27 +10208,31 @@ write_dso (DSO *dso, const char *file, struct stat *st)
dso->shdr[dso->ehdr.e_shstrndx].sh_size += len;
if (dso->shdr[dso->ehdr.e_shstrndx].sh_offset < min_shoff)
min_shoff = dso->shdr[dso->ehdr.e_shstrndx].sh_offset;
- for (j = dso->ehdr.e_shstrndx + 1; j < dso->ehdr.e_shnum; ++j)
- dso->shdr[j].sh_offset += len;
- if (ehdr.e_shoff > dso->shdr[dso->ehdr.e_shstrndx].sh_offset)
+ for (j = 1; j < dso->ehdr.e_shnum; ++j)
+ if (sorted_section_pos[j]
+ > sorted_section_pos[dso->ehdr.e_shstrndx])
+ dso->shdr[j].sh_offset += len;
+ if (!after_sht[dso->ehdr.e_shstrndx])
ehdr.e_shoff += len;
shstrtabadd += len;
diff = debug_sections[i].new_size;
addsize += diff;
off = dso->shdr[addsec].sh_offset;
+ off_index = addsec;
}
else
{
diff = (GElf_Off) debug_sections[i].new_size
- (GElf_Off) dso->shdr[debug_sections[i].sec].sh_size;
off = dso->shdr[debug_sections[i].sec].sh_offset;
+ off_index = debug_sections[i].sec;
}
if (off < min_shoff)
min_shoff = off;
for (j = 1; j < dso->ehdr.e_shnum; ++j)
- if (dso->shdr[j].sh_offset > off)
+ if (sorted_section_pos[j] > sorted_section_pos[off_index])
dso->shdr[j].sh_offset += diff;
- if (ehdr.e_shoff > off)
+ if (!after_sht[off_index])
ehdr.e_shoff += diff;
dso->shdr[debug_sections[i].sec].sh_size
= debug_sections[i].new_size;
@@ -10129,7 +10244,7 @@ write_dso (DSO *dso, const char *file, struct stat *st)
min_shoff = ehdr.e_shoff;
for (j = 1; j < dso->ehdr.e_shnum; ++j)
{
- if (dso->shdr[j].sh_offset > ehdr.e_shoff)
+ if (after_sht[j])
dso->shdr[j].sh_offset -= ehdr.e_shentsize;
if (dso->shdr[j].sh_link
> (unsigned int) debug_sections[i].sec)
@@ -10163,7 +10278,9 @@ write_dso (DSO *dso, const char *file, struct stat *st)
GElf_Off last_shoff = 0;
int k = -1;
bool shdr_placed = false;
- for (j = 1; j < dso->ehdr.e_shnum; ++j)
+ int l;
+ for (l = 1, j = sorted_section_numbers[l]; l < dso->ehdr.e_shnum;
+ ++l, j = sorted_section_numbers[l])
if (dso->shdr[j].sh_offset < min_shoff && !last_shoff)
continue;
else if ((dso->shdr[j].sh_flags & SHF_ALLOC) != 0)
@@ -10181,15 +10298,18 @@ write_dso (DSO *dso, const char *file, struct stat *st)
else
{
if (k == -1)
- k = j;
+ k = l;
last_shoff = dso->shdr[j].sh_offset + dso->shdr[j].sh_size;
}
last_shoff = min_shoff;
- for (j = k; j <= dso->ehdr.e_shnum; ++j)
+ for (l = k; l <= dso->ehdr.e_shnum; ++l)
{
+ j = (l == dso->ehdr.e_shnum
+ ? -1
+ : (int)sorted_section_numbers[l]);
if (!shdr_placed
&& ehdr.e_shoff >= min_shoff
- && (j == dso->ehdr.e_shnum
+ && (l == dso->ehdr.e_shnum
|| ehdr.e_shoff < dso->shdr[j].sh_offset))
{
if (ehdr.e_ident[EI_CLASS] == ELFCLASS64)
@@ -10199,7 +10319,7 @@ write_dso (DSO *dso, const char *file, struct stat *st)
last_shoff = ehdr.e_shoff + ehdr.e_shnum * ehdr.e_shentsize;
shdr_placed = true;
}
- if (j == dso->ehdr.e_shnum)
+ if (l == dso->ehdr.e_shnum)
break;
dso->shdr[j].sh_offset = last_shoff;
if (dso->shdr[j].sh_addralign > 1)
diff --git a/testsuite/dwz.tests/dwz-tests.exp b/testsuite/dwz.tests/dwz-tests.exp
index bea18fb..39eb661 100644
--- a/testsuite/dwz.tests/dwz-tests.exp
+++ b/testsuite/dwz.tests/dwz-tests.exp
@@ -5,8 +5,26 @@ set pwd [pwd]
set env(PATH) $pwd/$srcdir/scripts:$::env(PATH)
foreach test $tests {
- set dir [exec basename $test]
- set dir $pwd/tmp.$dir
+ set basename [exec basename $test]
+
+ set required_execs []
+ if { $basename == "gold-gdb-index.sh" } {
+ lappend required_execs "hello-gold-gdb-index"
+ }
+
+ set unsupported 0
+ foreach required_exec $required_execs {
+ set size [file size $required_exec]
+ if { $size == 0 } {
+ set unsupported 1
+ }
+ }
+ if { $unsupported == 1 } {
+ unsupported "$test"
+ continue
+ }
+
+ set dir $pwd/tmp.$basename
exec rm -Rf $dir
exec mkdir $dir
diff --git a/testsuite/dwz.tests/gold-gdb-index.sh b/testsuite/dwz.tests/gold-gdb-index.sh
new file mode 100755
index 0000000..cacc2b7
--- /dev/null
+++ b/testsuite/dwz.tests/gold-gdb-index.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+
+set -e
+
+cp ../hello-gold-gdb-index 1
+
+dwz 1
+
+smaller-than.sh 1 ../hello-gold-gdb-index
+
+[ $(ls) = "1" ]
+
+rm -f 1