Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
objtool: Fix weak symbol hole detection for .cold functions
When ignore_unreachable_insn() looks for weak function holes which jump
to their .cold functions, it assumes the parent function comes before
the corresponding .cold function in the symbol table. That's not
necessarily the case with -ffunction-sections.
Mark all the holes beforehand (including .cold functions) so the
ordering of the discovery doesn't matter.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
+45
-42
+43
-41
tools/objtool/check.c
+43
-41
tools/objtool/check.c
···
2507
2507
file->rodata = found;
2508
2508
}
2509
2509
2510
+
static void mark_holes(struct objtool_file *file)
2511
+
{
2512
+
struct instruction *insn;
2513
+
bool in_hole = false;
2514
+
2515
+
if (!opts.link)
2516
+
return;
2517
+
2518
+
/*
2519
+
* Whole archive runs might encounter dead code from weak symbols.
2520
+
* This is where the linker will have dropped the weak symbol in
2521
+
* favour of a regular symbol, but leaves the code in place.
2522
+
*/
2523
+
for_each_insn(file, insn) {
2524
+
if (insn->sym || !find_symbol_hole_containing(insn->sec, insn->offset)) {
2525
+
in_hole = false;
2526
+
continue;
2527
+
}
2528
+
2529
+
/* Skip function padding and pfx code */
2530
+
if (!in_hole && insn->type == INSN_NOP)
2531
+
continue;
2532
+
2533
+
in_hole = true;
2534
+
insn->hole = 1;
2535
+
2536
+
/*
2537
+
* If this hole jumps to a .cold function, mark it ignore.
2538
+
*/
2539
+
if (insn->jump_dest) {
2540
+
struct symbol *dest_func = insn_func(insn->jump_dest);
2541
+
2542
+
if (dest_func && dest_func->cold)
2543
+
dest_func->ignore = true;
2544
+
}
2545
+
}
2546
+
}
2547
+
2510
2548
static int decode_sections(struct objtool_file *file)
2511
2549
{
2512
2550
mark_rodata(file);
···
2597
2559
2598
2560
if (read_unwind_hints(file))
2599
2561
return -1;
2562
+
2563
+
/* Must be after add_jump_destinations() */
2564
+
mark_holes(file);
2600
2565
2601
2566
/*
2602
2567
* Must be after add_call_destinations() such that it can override
···
4062
4021
struct instruction *prev_insn;
4063
4022
int i;
4064
4023
4065
-
if (insn->type == INSN_NOP || insn->type == INSN_TRAP || (func && func->ignore))
4024
+
if (insn->type == INSN_NOP || insn->type == INSN_TRAP ||
4025
+
insn->hole || (func && func->ignore))
4066
4026
return true;
4067
4027
4068
4028
/*
···
4073
4031
if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4074
4032
!strcmp(insn->sec->name, ".altinstr_aux"))
4075
4033
return true;
4076
-
4077
-
/*
4078
-
* Whole archive runs might encounter dead code from weak symbols.
4079
-
* This is where the linker will have dropped the weak symbol in
4080
-
* favour of a regular symbol, but leaves the code in place.
4081
-
*
4082
-
* In this case we'll find a piece of code (whole function) that is not
4083
-
* covered by a !section symbol. Ignore them.
4084
-
*/
4085
-
if (opts.link && !func) {
4086
-
int size = find_symbol_hole_containing(insn->sec, insn->offset);
4087
-
unsigned long end = insn->offset + size;
4088
-
4089
-
if (!size) /* not a hole */
4090
-
return false;
4091
-
4092
-
if (size < 0) /* hole until the end */
4093
-
return true;
4094
-
4095
-
sec_for_each_insn_continue(file, insn) {
4096
-
/*
4097
-
* If we reach a visited instruction at or before the
4098
-
* end of the hole, ignore the unreachable.
4099
-
*/
4100
-
if (insn->visited)
4101
-
return true;
4102
-
4103
-
if (insn->offset >= end)
4104
-
break;
4105
-
4106
-
/*
4107
-
* If this hole jumps to a .cold function, mark it ignore too.
4108
-
*/
4109
-
if (insn->jump_dest && insn_func(insn->jump_dest) &&
4110
-
insn_func(insn->jump_dest)->cold)
4111
-
insn_func(insn->jump_dest)->ignore = true;
4112
-
}
4113
-
4114
-
return false;
4115
-
}
4116
4034
4117
4035
if (!func)
4118
4036
return false;