Message-ID: <CAK8P3a0t5s1CWAAW+EaVtsLFyS0XXhFio4-QHgg8Wpc6kdKaxA@mail.gmail.com>
Date:   Wed, 1 Mar 2017 23:05:39 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [PATCH] [RFC] x86: avoid -mtune=atom for objtool warnings

On Wed, Mar 1, 2017 at 5:53 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Wed, Mar 01, 2017 at 04:27:29PM +0100, Arnd Bergmann wrote:
>> On Wed, Mar 1, 2017 at 3:40 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>> > On Wed, Mar 01, 2017 at 10:45:03AM +0100, Arnd Bergmann wrote:
>>
>> >> Actually, something must have changed in gcc since last month, I also
>> >> just got a report in another file:
>> >>
>> >> drivers/i2c/busses/i2c-img-scb.o: warning: objtool: img_i2c_probe()
>> >> falls through to next function img_i2c_read_fifo()
>> >
>> > This one looks like it could be related to some recent objtool changes
>> > which affect how it interprets 'ud2'.  Which commit were you testing
>> > with?  Can you provide the .config file, and the object file if it's not
>> > too big?
>>
>> This is with my randconfig test series on top of latest linux-next.
>> I see it with the latest gcc-7.0.1 snapshot as well as an earlier gcc-7.0.0
>> build (20161201), but not with gcc-6.3.1
>
> I wonder if this is another gcc bug.  gcc inserted two ud2 instructions
> in img_i2c_probe() for no apparent reason.  Here's one of them:
>
>      5c3:       e8 00 00 00 00          callq  5c8 <img_i2c_probe+0x298>
>                         5c4: R_X86_64_PC32      dev_warn-0x4
>      5c8:       8b 05 00 00 00 00       mov    0x0(%rip),%eax        # 5ce <img_i2c_probe+0x29e>
>                         5ca: R_X86_64_PC32      .data+0xec
>      5ce:       89 83 70 06 00 00       mov    %eax,0x670(%rbx)
>      5d4:       0f 0b                   ud2
>
> Which corresponds to the following code block:
>
>         if (i2c->bitrate > timings[ARRAY_SIZE(timings) - 1].max_bitrate) {
>                 dev_warn(i2c->adap.dev.parent,
>                          "requested bitrate (%u) is higher than the max bitrate supported (%u)\n",
>                          i2c->bitrate,
>                          timings[ARRAY_SIZE(timings) - 1].max_bitrate);
>                 timing = timings[ARRAY_SIZE(timings) - 1];
>                 i2c->bitrate = timing.max_bitrate;
>         }
>
> I see no apparent reason for the ud2.
>
> Can you rebuild the object with CONFIG_DEBUG_INFO and use addr2line to
> see what code lines are associated with the ud2's?

$ addr2line -e drivers/i2c/busses/i2c-img-scb.o
0x5bc
/git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1187: i2c->bitrate =
timing.max_bitrate;
0x65d
/git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1181: if (i2c->bitrate >
timings[ARRAY_SIZE(timings) - 1].max_bitrate) {

and from the .s file with line numbers:

.type img_i2c_probe, @function
img_i2c_probe:
.LFB1968:
.loc 1 1323 0
.cfi_startproc
.LVL40:
1: call __fentry__
pushq %rbp #
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
.LBB757:
.LBB758:
# /git/arm-soc/include/linux/device.h:668: return devm_kmalloc(dev,
size, gfp | __GFP_ZERO);
.file 5 "/git/arm-soc/include/linux/device.h"
.loc 5 668 0
movl $21004480, %edx #,
movl $1992, %esi #,
.LBE758:
.LBE757:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1323: {
.loc 1 1323 0
movq %rsp, %rbp #,
.cfi_def_cfa_register 6
pushq %r15 #
pushq %r14 #
.cfi_offset 15, -24
.cfi_offset 14, -32
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1330: i2c =
devm_kzalloc(&pdev->dev, sizeof(struct img_i2c), GFP_KERNEL);
.loc 1 1330 0
leaq 16(%rdi), %r14 #, _1
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1323: {
.loc 1 1323 0
pushq %r13 #
pushq %r12 #
pushq %rbx #
.cfi_offset 13, -40
.cfi_offset 12, -48
.cfi_offset 3, -56
movq %rdi, %r12 # pdev, pdev
subq $24, %rsp #,
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1324: struct
device_node *node = pdev->dev.of_node;
.loc 1 1324 0
movq 864(%rdi), %r15 # pdev_19(D)->dev.of_node, node
.LVL41:
.LBB760:
.LBB759:
# /git/arm-soc/include/linux/device.h:668: return devm_kmalloc(dev,
size, gfp | __GFP_ZERO);
.loc 5 668 0
movq %r14, %rdi # _1,
.LVL42:
call devm_kmalloc #
.LVL43:
.LBE759:
.LBE760:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1331: if (!i2c)
.loc 1 1331 0
testq %rax, %rax # _29
je .L62 #,
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1334: res =
platform_get_resource(pdev, IORESOURCE_MEM, 0);
.loc 1 1334 0
xorl %edx, %edx #
movl $512, %esi #,
movq %r12, %rdi # pdev,
movq %rax, %rbx #, _29
call platform_get_resource #
.LVL44:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1335: i2c->base =
devm_ioremap_resource(&pdev->dev, res);
.loc 1 1335 0
movq %r14, %rdi # _1,
.LVL45:
movq %rax, %rsi # res,
call devm_ioremap_resource #
.LVL46:
.LBB761:
.LBB762:
# /git/arm-soc/include/linux/err.h:35: return IS_ERR_VALUE((unsigned long)ptr);
.file 6 "/git/arm-soc/include/linux/err.h"
.loc 6 35 0
xorl %esi, %esi # tmp128
cmpq $-4096, %rax #, _2
.LBE762:
.LBE761:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1335: i2c->base =
devm_ioremap_resource(&pdev->dev, res);
.loc 1 1335 0
movq %rax, %r13 #, _2
.LBB766:
.LBB764:
# /git/arm-soc/include/linux/err.h:35: return IS_ERR_VALUE((unsigned long)ptr);
.loc 6 35 0
seta %sil #, tmp128
.LBE764:
.LBE766:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1335: i2c->base =
devm_ioremap_resource(&pdev->dev, res);
.loc 1 1335 0
movq %rax, 1624(%rbx) # _2, MEM[(struct img_i2c *)_29].base
.LBB767:
.LBB765:
.LBB763:
# /git/arm-soc/include/linux/err.h:35: return IS_ERR_VALUE((unsigned long)ptr);
.loc 6 35 0
xorl %edx, %edx #
movq $______f.2078, %rdi #,
call ftrace_likely_update #
.LVL47:
.LBE763:
.LBE765:
.LBE767:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1336: if (IS_ERR(i2c->base))
.loc 1 1336 0
cmpq $-4096, %r13 #, _2
jbe .L54 #,
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1337: return PTR_ERR(i2c->base);
.loc 1 1337 0
movl 1624(%rbx), %r13d # MEM[(struct img_i2c *)_29].base, <retval>
.LVL48:
.L52:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1405: }
.loc 1 1405 0
addq $24, %rsp #,
movl %r13d, %eax # <retval>,
popq %rbx #
.cfi_remember_state
.cfi_restore 3
popq %r12 #
.cfi_restore 12
.LVL49:
popq %r13 #
.cfi_restore 13
popq %r14 #
.cfi_restore 14
popq %r15 #
.cfi_restore 15
.LVL50:
popq %rbp #
.cfi_restore 6
.cfi_def_cfa 7, 8
ret
.LVL51:
.L54:
.cfi_restore_state
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1339: irq =
platform_get_irq(pdev, 0);
.loc 1 1339 0
xorl %esi, %esi #
movq %r12, %rdi # pdev,
call platform_get_irq #
.LVL52:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1340: if (irq < 0) {
.loc 1 1340 0
testl %eax, %eax # <retval>
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1339: irq =
platform_get_irq(pdev, 0);
.loc 1 1339 0
movl %eax, %r13d #, <retval>
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1340: if (irq < 0) {
.loc 1 1340 0
js .L65 #,
.LBB768:
.LBB769:
# /git/arm-soc/include/linux/interrupt.h:173: return
devm_request_threaded_irq(dev, irq, handler, NULL, irqflags,
.file 7 "/git/arm-soc/include/linux/interrupt.h"
.loc 7 173 0
movq (%r12), %r9 # pdev_19(D)->name,
.LBE769:
.LBE768:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1345: i2c->sys_clk =
devm_clk_get(&pdev->dev, "sys");
.loc 1 1345 0
movq $0, 1640(%rbx) #, MEM[(struct img_i2c *)_29].sys_clk
.LBB772:
.LBB770:
# /git/arm-soc/include/linux/interrupt.h:173: return
devm_request_threaded_irq(dev, irq, handler, NULL, irqflags,
.loc 7 173 0
xorl %r8d, %r8d #
.LBE770:
.LBE772:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1351: i2c->scb_clk =
devm_clk_get(&pdev->dev, "scb");
.loc 1 1351 0
movq $0, 1632(%rbx) #, MEM[(struct img_i2c *)_29].scb_clk
.LBB773:
.LBB771:
# /git/arm-soc/include/linux/interrupt.h:173: return
devm_request_threaded_irq(dev, irq, handler, NULL, irqflags,
.loc 7 173 0
xorl %ecx, %ecx #
movq %rbx, (%rsp) # _29,
movq $img_i2c_isr, %rdx #,
movl %eax, %esi # <retval>,
movq %r14, %rdi # _1,
call devm_request_threaded_irq #
.LVL53:
.LBE771:
.LBE773:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1359: if (ret) {
.loc 1 1359 0
testl %eax, %eax # _62
movl %eax, -52(%rbp) # _62, %sfp
jne .L66 #,
.LBB774:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1365:
init_timer(&i2c->check_timer);
.loc 1 1365 0
leaq 1864(%rbx), %rdi #, tmp131
xorl %esi, %esi #
movq $__key.25244, %rcx #,
movq $.LC7, %rdx #,
call init_timer_key #
.LVL54:
.LBE774:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1369: i2c->bitrate =
timings[0].max_bitrate;
.loc 1 1369 0
movl timings+8(%rip), %eax # timings[0].max_bitrate, timings[0].max_bitrate
.LBB775:
.LBB776:
.LBB777:
# /git/arm-soc/include/linux/of.h:458: int ret =
of_property_read_variable_u32_array(np, propname, out_values,
.file 8 "/git/arm-soc/include/linux/of.h"
.loc 8 458 0
leaq -44(%rbp), %rdx #, tmp161
xorl %r8d, %r8d #
.LBE777:
.LBE776:
.LBE775:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1366:
i2c->check_timer.function = img_i2c_check_timer;
.loc 1 1366 0
movq $img_i2c_check_timer, 1888(%rbx) #, MEM[(struct img_i2c
*)_29].check_timer.function
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1367:
i2c->check_timer.data = (unsigned long)i2c;
.loc 1 1367 0
movq %rbx, 1896(%rbx) # _29, MEM[(struct img_i2c *)_29].check_timer.data
.LBB782:
.LBB780:
.LBB778:
# /git/arm-soc/include/linux/of.h:458: int ret =
of_property_read_variable_u32_array(np, propname, out_values,
.loc 8 458 0
movl $1, %ecx #,
movq $.LC8, %rsi #,
movq %r15, %rdi # node,
.LBE778:
.LBE780:
.LBE782:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1369: i2c->bitrate =
timings[0].max_bitrate;
.loc 1 1369 0
movl %eax, 1648(%rbx) # timings[0].max_bitrate, MEM[(struct img_i2c
*)_29].bitrate
.LBB783:
.LBB781:
.LBB779:
# /git/arm-soc/include/linux/of.h:458: int ret =
of_property_read_variable_u32_array(np, propname, out_values,
.loc 8 458 0
call of_property_read_variable_u32_array #
.LVL55:
# /git/arm-soc/include/linux/of.h:460: if (ret >= 0)
.loc 8 460 0
testl %eax, %eax # ret
js .L57 #,
.LVL56:
.LBE779:
.LBE781:
.LBE783:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1371: i2c->bitrate = val;
.loc 1 1371 0
movl -44(%rbp), %eax # val, val
.LVL57:
movl %eax, 1648(%rbx) # val, MEM[(struct img_i2c *)_29].bitrate
.LVL58:
.L57:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1379: i2c->adap.nr = pdev->id;
.loc 1 1379 0
movl 8(%r12), %eax # pdev_19(D)->id, pdev_19(D)->id
.LVL59:
.LBB784:
.LBB785:
# /git/arm-soc/include/linux/spinlock.h:288: return &lock->rlock;
.loc 4 288 0
leaq 1752(%rbx), %rdi #, tmp142
.LBE785:
.LBE784:
.LBB786:
.LBB787:
.LBB788:
# /git/arm-soc/include/linux/device.h:1033: dev->driver_data = data;
.loc 5 1033 0
movq %rbx, 512(%rbx) # _29, MEM[(struct device *)_29 + 240B].driver_data
.LBE788:
.LBE787:
.LBE786:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1374:
i2c->adap.dev.parent = &pdev->dev;
.loc 1 1374 0
movq %r14, 240(%rbx) # _1, MEM[(struct img_i2c *)_29].adap.dev.parent
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1375:
i2c->adap.dev.of_node = node;
.loc 1 1375 0
movq %r15, 1088(%rbx) # node, MEM[(struct img_i2c *)_29].adap.dev.of_node
.LBB789:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1383:
spin_lock_init(&i2c->lock);
.loc 1 1383 0
movq $__key.25245, %rdx #,
.LBE789:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1376: i2c->adap.owner
= THIS_MODULE;
.loc 1 1376 0
movq $__this_module, (%rbx) #, MEM[(struct img_i2c *)_29].adap.owner
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1377: i2c->adap.algo =
&img_i2c_algo;
.loc 1 1377 0
movq $img_i2c_algo, 16(%rbx) #, MEM[(struct img_i2c *)_29].adap.algo
.LBB790:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1383:
spin_lock_init(&i2c->lock);
.loc 1 1383 0
movq $.LC9, %rsi #,
.LBE790:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1379: i2c->adap.nr = pdev->id;
.loc 1 1379 0
movl %eax, 1280(%rbx) # pdev_19(D)->id, MEM[(struct img_i2c *)_29].adap.nr
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1380:
snprintf(i2c->adap.name, sizeof(i2c->adap.name), "IMG SCB I2C");
.loc 1 1380 0
movabsq $2324494381979487561, %rax #, tmp162
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1378: i2c->adap.retries = 5;
.loc 1 1378 0
movl $5, 236(%rbx) #, MEM[(struct img_i2c *)_29].adap.retries
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1380:
snprintf(i2c->adap.name, sizeof(i2c->adap.name), "IMG SCB I2C");
.loc 1 1380 0
movq %rax, 1284(%rbx) # tmp162, MEM[(void *)_29 + 1284B]
movl $4403785, 1292(%rbx) #, MEM[(void *)_29 + 1284B]
.LBB791:
.LBB792:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:443: i2c->mode = mode;
.loc 1 443 0
movl $0, 1848(%rbx) #, MEM[(struct img_i2c *)_29].mode
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:444: i2c->int_enable =
img_i2c_int_enable_by_mode[mode];
.loc 1 444 0
movq $0, 1852(%rbx) #, MEM[(unsigned int *)_29 + 1852B]
.LBE792:
.LBE791:
.LBB793:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1383:
spin_lock_init(&i2c->lock);
.loc 1 1383 0
call __raw_spin_lock_init #
.LVL60:
.LBE793:
.LBB794:
.LBB795:
.LBB796:
# /git/arm-soc/include/linux/completion.h:79: init_waitqueue_head(&x->wait);
.file 9 "/git/arm-soc/include/linux/completion.h"
.loc 9 79 0
leaq 1664(%rbx), %rdi #, tmp144
.LBE796:
# /git/arm-soc/include/linux/completion.h:78: x->done = 0;
.loc 9 78 0
movl $0, 1656(%rbx) #, MEM[(struct completion *)_29 + 1656B].done
.LBB797:
# /git/arm-soc/include/linux/completion.h:79: init_waitqueue_head(&x->wait);
.loc 9 79 0
movq $__key.8818, %rdx #,
movq $.LC10, %rsi #,
call __init_waitqueue_head #
.LVL61:
.LBE797:
.LBE795:
.LBE794:
.LBB798:
.LBB799:
.LBB800:
.LBB801:
# /git/arm-soc/include/linux/clk.h:191: might_sleep();
.loc 2 191 0
xorl %edx, %edx #
.LBE801:
.LBE800:
.LBE799:
.LBE798:
.LBB805:
.LBB806:
.LBB807:
# /git/arm-soc/include/linux/device.h:1033: dev->driver_data = data;
.loc 5 1033 0
movq %rbx, 288(%r12) # _29, MEM[(struct device *)pdev_19(D) + 16B].driver_data
.LBE807:
.LBE806:
.LBE805:
.LBB808:
.LBB804:
.LBB803:
.LBB802:
# /git/arm-soc/include/linux/clk.h:191: might_sleep();
.loc 2 191 0
movl $191, %esi #,
movq $.LC0, %rdi #,
call __might_sleep #
.LVL62:
.LBE802:
.LBE803:
.LBE804:
.LBE808:
.LBB809:
.LBB810:
.LBB811:
.LBB812:
.LBB813:
.LBB814:
xorl %edx, %edx #
movl $191, %esi #,
movq $.LC0, %rdi #,
call __might_sleep #
.LVL63:
.LBE814:
.LBE813:
.LBE812:
.LBE811:
.LBB815:
.LBB816:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:418: return
readl(i2c->base + offset);
.loc 1 418 0
movq 1624(%rbx), %rax # MEM[(struct img_i2c *)_29].base, MEM[(struct
img_i2c *)_29].base
.LBB817:
.LBB818:
# /git/arm-soc/arch/x86/include/asm/io.h:58: build_mmio_read(readl,
"l", unsigned int, "=r", :"memory")
.loc 3 58 0
#APP
# 58 "/git/arm-soc/arch/x86/include/asm/io.h" 1
movl 128(%rax),%eax # MEM[(volatile unsigned int *)_81], ret
# 0 "" 2
.LVL64:
#NO_APP
.LBE818:
.LBE817:
.LBE816:
.LBE815:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1161: if ((rev &
0x00ffffff) < 0x00020200) {
.loc 1 1161 0
movl %eax, %edx # ret, tmp147
andl $16777215, %edx #, tmp147
cmpl $131583, %edx #, tmp147
jbe .L67 #,
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1176: if (i2c->bitrate
<= timings[i].max_bitrate) {
.loc 1 1176 0
movl 1648(%rbx), %edx # MEM[(struct img_i2c *)_29].bitrate, _99
cmpl timings+8(%rip), %edx # timings[0].max_bitrate, _99
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1171:
i2c->need_wr_rd_fence = true;
.loc 1 1171 0
movb $1, 1652(%rbx) #, MEM[(struct img_i2c *)_29].need_wr_rd_fence
movl timings+48(%rip), %ecx # timings[1].max_bitrate, pretmp_260
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1176: if (i2c->bitrate
<= timings[i].max_bitrate) {
.loc 1 1176 0
jbe .L59 #,
cmpl %ecx, %edx # pretmp_260, _99
jbe .L60 #,
.L61:
.LBB819:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1182:
dev_warn(i2c->adap.dev.parent,
.loc 1 1182 0
movq 240(%rbx), %rdi # MEM[(struct img_i2c *)_29].adap.dev.parent,
MEM[(struct img_i2c *)_29].adap.dev.parent
movq $.LC12, %rsi #,
call dev_warn #
.LVL65:
# /git/arm-soc/drivers/i2c/busses/i2c-img-scb.c:1187: i2c->bitrate =
timing.max_bitrate;
.loc 1 1187 0
movl timings+48(%rip), %eax # MEM[(struct img_i2c_timings *)&timings +
48B], MEM[(struct img_i2c_timings *)&timings + 48B]
movl %eax, 1648(%rbx) # MEM[(struct img_i2c_timings *)&timings + 48B],
MEM[(struct img_i2c *)_29].bitrate
.LVL66:
.L60:
ud2
.LVL67:
.L66:
.LBE819:
.LBE810:
.LBE809:

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