Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
objtool: Handle Clang RSP musical chairs
For no apparent reason (possibly related to CONFIG_KMSAN), Clang can
randomly pass the value of RSP to other registers and then back again to
RSP. Handle that accordingly.
Fixes the following warnings:
drivers/input/misc/uinput.o: warning: objtool: uinput_str_to_user+0x165: undefined stack state
drivers/input/misc/uinput.o: warning: objtool: uinput_str_to_user+0x165: unknown CFA base reg -1
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/90956545-2066-46e3-b547-10c884582eb0@app.fastmail.com
Link: https://patch.msgid.link/240e6a172cc73292499334a3724d02ccb3247fc7.1772818491.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
+40
-42
+26
-42
tools/objtool/arch/x86/decode.c
+26
-42
tools/objtool/arch/x86/decode.c
···
395
395
if (!rex_w)
396
396
break;
397
397
398
-
if (modrm_reg == CFI_SP) {
399
-
400
-
if (mod_is_reg()) {
401
-
/* mov %rsp, reg */
402
-
ADD_OP(op) {
403
-
op->src.type = OP_SRC_REG;
404
-
op->src.reg = CFI_SP;
405
-
op->dest.type = OP_DEST_REG;
406
-
op->dest.reg = modrm_rm;
407
-
}
408
-
break;
409
-
410
-
} else {
411
-
/* skip RIP relative displacement */
412
-
if (is_RIP())
413
-
break;
414
-
415
-
/* skip nontrivial SIB */
416
-
if (have_SIB()) {
417
-
modrm_rm = sib_base;
418
-
if (sib_index != CFI_SP)
419
-
break;
420
-
}
421
-
422
-
/* mov %rsp, disp(%reg) */
423
-
ADD_OP(op) {
424
-
op->src.type = OP_SRC_REG;
425
-
op->src.reg = CFI_SP;
426
-
op->dest.type = OP_DEST_REG_INDIRECT;
427
-
op->dest.reg = modrm_rm;
428
-
op->dest.offset = ins.displacement.value;
429
-
}
430
-
break;
431
-
}
432
-
433
-
break;
434
-
}
435
-
436
-
if (rm_is_reg(CFI_SP)) {
437
-
438
-
/* mov reg, %rsp */
398
+
if (mod_is_reg()) {
399
+
/* mov reg, reg */
439
400
ADD_OP(op) {
440
401
op->src.type = OP_SRC_REG;
441
402
op->src.reg = modrm_reg;
442
403
op->dest.type = OP_DEST_REG;
443
-
op->dest.reg = CFI_SP;
404
+
op->dest.reg = modrm_rm;
405
+
}
406
+
break;
407
+
}
408
+
409
+
/* skip RIP relative displacement */
410
+
if (is_RIP())
411
+
break;
412
+
413
+
/* skip nontrivial SIB */
414
+
if (have_SIB()) {
415
+
modrm_rm = sib_base;
416
+
if (sib_index != CFI_SP)
417
+
break;
418
+
}
419
+
420
+
/* mov %rsp, disp(%reg) */
421
+
if (modrm_reg == CFI_SP) {
422
+
ADD_OP(op) {
423
+
op->src.type = OP_SRC_REG;
424
+
op->src.reg = CFI_SP;
425
+
op->dest.type = OP_DEST_REG_INDIRECT;
426
+
op->dest.reg = modrm_rm;
427
+
op->dest.offset = ins.displacement.value;
444
428
}
445
429
break;
446
430
}
+14
tools/objtool/check.c
+14
tools/objtool/check.c
···
3000
3000
cfi->stack_size += 8;
3001
3001
}
3002
3002
3003
+
else if (cfi->vals[op->src.reg].base == CFI_CFA) {
3004
+
/*
3005
+
* Clang RSP musical chairs:
3006
+
*
3007
+
* mov %rsp, %rdx [handled above]
3008
+
* ...
3009
+
* mov %rdx, %rbx [handled here]
3010
+
* ...
3011
+
* mov %rbx, %rsp [handled above]
3012
+
*/
3013
+
cfi->vals[op->dest.reg].base = CFI_CFA;
3014
+
cfi->vals[op->dest.reg].offset = cfi->vals[op->src.reg].offset;
3015
+
}
3016
+
3003
3017
3004
3018
break;
3005
3019