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detect and ignore might_sleep line number changes

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When CONFIG_DEBUG_ATOMIC_SLEEP is enabled, might_sleep calls will add
the line number to the instruction stream.  Detect and ignore any such
changes.

Fixes: #657.
This commit is contained in:
Joe Lawrence 2017-02-02 09:56:06 -05:00
parent c54b64aa7b
commit 99f7792fdc
1 changed files with 23 additions and 13 deletions
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36
kpatch-build/create-diff-object.c
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@ -226,13 +226,13 @@ out:
}
/*
* Determine if a section has changed only due to a WARN* macro call's
* embedding of the line number into an instruction operand.
* Determine if a section has changed only due to a WARN* or might_sleep
* macro call's embedding of the line number into an instruction operand.
*
* Warning: Hackery lies herein. It's hopefully justified by the fact that
* this issue is very common.
*
* Example:
* Example WARN*:
*
* 938: be 70 00 00 00 mov $0x70,%esi
* 93d: 48 c7 c7 00 00 00 00 mov $0x0,%rdi
@ -242,18 +242,26 @@ out:
* 94b: e8 00 00 00 00 callq 950 <tcp_conn_request+0x950>
* 94c: R_X86_64_PC32 warn_slowpath_null-0x4
*
* Example might_sleep:
*
* 50f: be f7 01 00 00 mov $0x1f7,%esi
* 514: 48 c7 c7 00 00 00 00 mov $0x0,%rdi
* 517: R_X86_64_32S .rodata.do_select.str1.8+0x98
* 51b: e8 00 00 00 00 callq 520 <do_select+0x520>
* 51c: R_X86_64_PC32 ___might_sleep-0x4
*
* The pattern which applies to all cases:
* 1) immediate move of the line number to %esi
* 2) (optional) string section rela
* 3) (optional) __warned.xxxxx static local rela
* 4) warn_slowpath_* rela
* 4) warn_slowpath_* or __might_sleep or ___might_sleep rela
*/
static int kpatch_warn_only_change(struct section *sec)
static int kpatch_line_macro_change_only(struct section *sec)
{
struct insn insn1, insn2;
unsigned long start1, start2, size, offset, length;
struct rela *rela;
int warnonly = 0, found;
int lineonly = 0, found;
if (sec->status != CHANGED ||
is_rela_section(sec) ||
@ -292,7 +300,7 @@ static int kpatch_warn_only_change(struct section *sec)
/*
* Verify zero or more string relas followed by a
* warn_slowpath_* rela.
* warn_slowpath_* or __might_sleep or ___might_sleep rela.
*/
found = 0;
list_for_each_entry(rela, &sec->rela->relas, list) {
@ -302,7 +310,9 @@ static int kpatch_warn_only_change(struct section *sec)
continue;
if (!strncmp(rela->sym->name, "__warned.", 9))
continue;
if (!strncmp(rela->sym->name, "warn_slowpath_", 14)) {
if (!strncmp(rela->sym->name, "warn_slowpath_", 14) ||
(!strcmp(rela->sym->name, "__might_sleep")) ||
(!strcmp(rela->sym->name, "___might_sleep"))) {
found = 1;
break;
}
@ -311,10 +321,10 @@ static int kpatch_warn_only_change(struct section *sec)
if (!found)
return 0;
warnonly = 1;
lineonly = 1;
}
if (!warnonly)
if (!lineonly)
ERROR("no instruction changes detected for changed section %s",
sec->name);
@ -333,10 +343,10 @@ static void kpatch_compare_sections(struct list_head *seclist)
sec->status = NEW;
}
/* exclude WARN-only changes */
/* exclude WARN-only, might_sleep changes */
list_for_each_entry(sec, seclist, list) {
if (kpatch_warn_only_change(sec)) {
log_debug("reverting WARN-only section %s status to SAME\n",
if (kpatch_line_macro_change_only(sec)) {
log_debug("reverting macro / line number section %s status to SAME\n",
sec->name);
sec->status = SAME;
}