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create-diff-object: add jump label support

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Add support for jump labels, also known as static jumps, static keys,
static branches, and jump tables.  Luckily,
kpatch_process_special_sections() is already generic enough to make this
an easy fix.

Fixes: #931

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Josh Poimboeuf 2019-01-29 13:08:21 -06:00
parent d8a44076f8
commit 87c64519fc
3 changed files with 44 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
kpatch-build/create-diff-object.c
View File

@ -1771,6 +1771,21 @@ static int ex_table_group_size(struct kpatch_elf *kelf, int offset)
return size;
}
static int jump_table_group_size(struct kpatch_elf *kelf, int offset)
{
static int size = 0;
char *str;
if (!size) {
str = getenv("JUMP_STRUCT_SIZE");
if (!str)
ERROR("JUMP_STRUCT_SIZE not set");
size = atoi(str);
}
return size;
}
#ifdef __x86_64__
static int parainstructions_group_size(struct kpatch_elf *kelf, int offset)
{
@ -1890,6 +1905,10 @@ static struct special_section special_sections[] = {
.name = "__ex_table", /* must come after .fixup */
.group_size = ex_table_group_size,
},
{
.name = "__jump_table",
.group_size = jump_table_group_size,
},
#ifdef __x86_64__
{
.name = ".smp_locks",
@ -2431,12 +2450,11 @@ static void kpatch_process_special_sections(struct kpatch_elf *kelf)
* The following special sections aren't supported, so make sure we
* don't ever try to include them. Otherwise the kernel will see the
* jump table during module loading and get confused. Generally it
* should be safe to exclude them, it just means that you can't modify
* jump labels and enable tracepoints in a patched function.
* should be safe to exclude them, it just means that tracepoints won't
* work in a patched function.
*/
list_for_each_entry(sec, &kelf->sections, list) {
if (strcmp(sec->name, "__jump_table") &&
strcmp(sec->name, "__tracepoints") &&
if (strcmp(sec->name, "__tracepoints") &&
strcmp(sec->name, "__tracepoints_ptrs") &&
strcmp(sec->name, "__tracepoints_strings"))
continue;

25
kpatch-build/kpatch-build
View File

@ -227,33 +227,40 @@ gcc_version_check() {
}
find_special_section_data_ppc64le() {
[[ "$CONFIG_JUMP_LABEL" -eq 0 ]] && AWK_OPTIONS="-vskip_j=1"
SPECIAL_VARS="$(readelf -wi "$VMLINUX" |
gawk --non-decimal-data '
BEGIN { f = b = e = 0 }
BEGIN { f = b = e = j = 0 }
# Set state if name matches
f == 0 && /DW_AT_name.* fixup_entry[[:space:]]*$/ {f = 1; next}
b == 0 && /DW_AT_name.* bug_entry[[:space:]]*$/ {b = 1; next}
e == 0 && /DW_AT_name.* exception_table_entry[[:space:]]*$/ {e = 1; next}
j == 0 && /DW_AT_name.* jump_entry[[:space:]]*$/ {j = 1; next}
# Reset state unless this abbrev describes the struct size
f == 1 && !/DW_AT_byte_size/ { f = 0; next }
b == 1 && !/DW_AT_byte_size/ { b = 0; next }
e == 1 && !/DW_AT_byte_size/ { e = 0; next }
j == 1 && !/DW_AT_byte_size/ { j = 0; next }
# Now that we know the size, stop parsing for it
f == 1 {printf("export FIXUP_STRUCT_SIZE=%d\n", $4); f = 2}
b == 1 {printf("export BUG_STRUCT_SIZE=%d\n", $4); b = 2}
e == 1 {printf("export EX_STRUCT_SIZE=%d\n", $4); e = 2}
j == 1 {printf("export JUMP_STRUCT_SIZE=%d\n", $4); j = 2}
# Bail out once we have everything
f == 2 && b == 2 && e == 2 {exit}')"
f == 2 && b == 2 && e == 2 && (j == 2 || skip_j) {exit}')"
[[ -n "$SPECIAL_VARS" ]] && eval "$SPECIAL_VARS"
[[ -z "$FIXUP_STRUCT_SIZE" ]] && die "can't find special struct fixup_entry size"
[[ -z "$BUG_STRUCT_SIZE" ]] && die "can't find special struct bug_entry size"
[[ -z "$EX_STRUCT_SIZE" ]] && die "can't find special struct exception_table_entry size"
[[ -z "$JUMP_STRUCT_SIZE" && "$CONFIG_JUMP_LABEL" -ne 0 ]] && die "can't find special struct jump_entry size"
return
}
@ -266,12 +273,13 @@ find_special_section_data() {
[[ "$CONFIG_PARAVIRT" -eq 0 ]] && AWK_OPTIONS="-vskip_p=1"
[[ "$CONFIG_UNWINDER_ORC" -eq 0 ]] && AWK_OPTIONS="$AWK_OPTIONS -vskip_o=1"
[[ "$CONFIG_JUMP_LABEL" -eq 0 ]] && AWK_OPTIONS="$AWK_OPTIONS -vskip_j=1"
# If $AWK_OPTIONS are blank gawk would treat "" as a blank script
# shellcheck disable=SC2086
SPECIAL_VARS="$(readelf -wi "$VMLINUX" |
gawk --non-decimal-data $AWK_OPTIONS '
BEGIN { a = b = p = e = o = 0 }
BEGIN { a = b = p = e = o = j = 0 }
# Set state if name matches
a == 0 && /DW_AT_name.* alt_instr[[:space:]]*$/ {a = 1; next}
@ -279,6 +287,7 @@ find_special_section_data() {
p == 0 && /DW_AT_name.* paravirt_patch_site[[:space:]]*$/ {p = 1; next}
e == 0 && /DW_AT_name.* exception_table_entry[[:space:]]*$/ {e = 1; next}
o == 0 && /DW_AT_name.* orc_entry[[:space:]]*$/ {o = 1; next}
j == 0 && /DW_AT_name.* jump_entry[[:space:]]*$/ {j = 1; next}
# Reset state unless this abbrev describes the struct size
a == 1 && !/DW_AT_byte_size/ { a = 0; next }
@ -286,6 +295,7 @@ find_special_section_data() {
p == 1 && !/DW_AT_byte_size/ { p = 0; next }
e == 1 && !/DW_AT_byte_size/ { e = 0; next }
o == 1 && !/DW_AT_byte_size/ { o = 0; next }
j == 1 && !/DW_AT_byte_size/ { j = 0; next }
# Now that we know the size, stop parsing for it
a == 1 {printf("export ALT_STRUCT_SIZE=%d\n", $4); a = 2}
@ -293,9 +303,10 @@ find_special_section_data() {
p == 1 {printf("export PARA_STRUCT_SIZE=%d\n", $4); p = 2}
e == 1 {printf("export EX_STRUCT_SIZE=%d\n", $4); e = 2}
o == 1 {printf("export ORC_STRUCT_SIZE=%d\n", $4); o = 2}
j == 1 {printf("export JUMP_STRUCT_SIZE=%d\n", $4); j = 2}
# Bail out once we have everything
a == 2 && b == 2 && (p == 2 || skip_p) && e == 2 && (o == 2 || skip_o) {exit}')"
a == 2 && b == 2 && (p == 2 || skip_p) && e == 2 && (o == 2 || skip_o) && (j == 2 || skip_j) {exit}')"
[[ -n "$SPECIAL_VARS" ]] && eval "$SPECIAL_VARS"
@ -304,6 +315,7 @@ find_special_section_data() {
[[ -z "$EX_STRUCT_SIZE" ]] && die "can't find special struct paravirt_patch_site size"
[[ -z "$PARA_STRUCT_SIZE" && "$CONFIG_PARAVIRT" -ne 0 ]] && die "can't find special struct paravirt_patch_site size"
[[ -z "$ORC_STRUCT_SIZE" && "$CONFIG_UNWINDER_ORC" -ne 0 ]] && die "can't find special struct orc_entry size"
[[ -z "$JUMP_STRUCT_SIZE" && "$CONFIG_JUMP_LABEL" -ne 0 ]] && die "can't find special struct jump_entry size"
return
}
@ -714,6 +726,11 @@ if grep -q "CONFIG_UNWINDER_ORC=y" "$CONFIGFILE"; then
else
CONFIG_UNWINDER_ORC=0
fi
if grep -q "CONFIG_JUMP_LABEL=y" "$CONFIGFILE"; then
CONFIG_JUMP_LABEL=1
else
CONFIG_JUMP_LABEL=0
fi
# unsupported kernel option checking
grep -q "CONFIG_DEBUG_INFO_SPLIT=y" "$CONFIGFILE" && die "kernel option 'CONFIG_DEBUG_INFO_SPLIT' not supported"

2
test/unit/objs

@ -1 +1 @@
Subproject commit 9a5663f9b52f6f99036185fa1a8e73ab6496abda
Subproject commit 3f91f6940e8eb71864a90970ef88d73c30966796