[kbuild-all] arch/x86/kvm/../../../virt/kvm/binary_stats.c:139:3: warning: Value stored to 'remain' is never read [clang-analyzer-deadcode.DeadStores]

Tuesday, 10 August 2021



tree: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   36a21d51725af2ce0700c6ebcb6b9594aac658a6
commit: cb082bfab59a224a49ae803fed52cd03e8d6b5e0 KVM: stats: Add 
fd-based API to read binary stats data
date:   7 weeks ago
:::::: branch date: 23 hours ago
:::::: commit date: 7 weeks ago
config: x86_64-randconfig-c001-20210806 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 
42b9c2a17a0b63cccf3ac197a82f91b28e53e643)
reproduce (this is a W=1 build):
         wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross 
-O ~/bin/make.cross
         chmod +x ~/bin/make.cross
         # install x86_64 cross compiling tool for clang build
         # apt-get install binutils-x86-64-linux-gnu
         # 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit...
         git remote add linus 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
         git fetch --no-tags linus master
         git checkout cb082bfab59a224a49ae803fed52cd03e8d6b5e0
         # save the attached .config to linux build tree
         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross 
ARCH=x86_64 clang-analyzer
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp(a)intel.com&gt;


clang-analyzer warnings: (new ones prefixed by >>)
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:206:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:207:34: warning: Value 
stored to 'c' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct dtv_frontend_properties *c = &fe->dtv_property_cache;
                                            ^   ~~~~~~~~~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:207:34: note: Value 
stored to 'c' during its initialization is never read
            struct dtv_frontend_properties *c = &fe->dtv_property_cache;
                                            ^   ~~~~~~~~~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:220:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:220:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:236:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:236:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:252:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:252:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:253:34: warning: Value 
stored to 'c' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct dtv_frontend_properties *c = &fe->dtv_property_cache;
                                            ^   ~~~~~~~~~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:253:34: note: Value 
stored to 'c' during its initialization is never read
            struct dtv_frontend_properties *c = &fe->dtv_property_cache;
                                            ^   ~~~~~~~~~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:270:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:270:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:297:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:297:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:323:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:323:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:413:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:413:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:425:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:425:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:439:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:439:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:455:21: warning: Value 
stored to 'client' during its initialization is never read 
[clang-analyzer-deadcode.DeadStores]
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    drivers/media/dvb-frontends/cxd2820r_core.c:455:21: note: Value 
stored to 'client' during its initialization is never read
            struct i2c_client *client = priv->client[0];
                               ^~~~~~   ~~~~~~~~~~~~~~~
    Suppressed 2 warnings (2 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    5 warnings generated.
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    6 warnings generated.
    arch/x86/kvm/../../../virt/kvm/eventfd.c:385:2: warning: Value 
stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores]
            ret = 0;
            ^     ~
    arch/x86/kvm/../../../virt/kvm/eventfd.c:385:2: note: Value stored 
to 'ret' is never read
            ret = 0;
            ^     ~
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    5 warnings generated.
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    5 warnings generated.
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    6 warnings generated.
    Suppressed 6 warnings (5 in non-user code, 1 with check filters).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    7 warnings generated.
...
> arch/x86/kvm/../../../virt/kvm/binary_stats.c:139:3: warning:
Value stored to 'remain' is never read [clang-analyzer-deadcode.DeadStores] 
                   remain -= copylen;
                    ^         ~~~~~~~
    arch/x86/kvm/../../../virt/kvm/binary_stats.c:139:3: note: Value 
stored to 'remain' is never read
                    remain -= copylen;
                    ^         ~~~~~~~
...
> arch/x86/kvm/../../../virt/kvm/binary_stats.c:141:3: warning:
Value stored to 'dest' is never read [clang-analyzer-deadcode.DeadStores]   
                 dest += copylen;
                    ^       ~~~~~~~
    arch/x86/kvm/../../../virt/kvm/binary_stats.c:141:3: note: Value 
stored to 'dest' is never read
                    dest += copylen;
                    ^       ~~~~~~~
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    5 warnings generated.
    Suppressed 5 warnings (5 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    7 warnings generated.
    Suppressed 7 warnings (7 in non-user code).
    Use -header-filter=.* to display errors from all non-system headers. 
Use -system-headers to display errors from system headers as well.
    7 warnings generated.
    arch/x86/kvm/emulate.c:1521:9: warning: 2nd function call argument 
is an uninitialized value [clang-analyzer-core.CallAndMessage]
            return linear_read_system(ctxt, *desc_addr_p, desc, 
sizeof(*desc));
                   ^
    arch/x86/kvm/emulate.c:3671:6: note: Assuming field 'modrm_reg' is 
not equal to VCPU_SREG_CS
            if (ctxt->modrm_reg == VCPU_SREG_CS || ctxt->modrm_reg > 
VCPU_SREG_GS)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:3671:6: note: Left side of '||' is false
    arch/x86/kvm/emulate.c:3671:41: note: Assuming field 'modrm_reg' is 
<= VCPU_SREG_GS
            if (ctxt->modrm_reg == VCPU_SREG_CS || ctxt->modrm_reg > 
VCPU_SREG_GS)
 
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:3671:2: note: Taking false branch
            if (ctxt->modrm_reg == VCPU_SREG_CS || ctxt->modrm_reg > 
VCPU_SREG_GS)
            ^
    arch/x86/kvm/emulate.c:3674:6: note: Assuming field 'modrm_reg' is 
not equal to VCPU_SREG_SS
            if (ctxt->modrm_reg == VCPU_SREG_SS)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:3674:2: note: Taking false branch
            if (ctxt->modrm_reg == VCPU_SREG_SS)
            ^
    arch/x86/kvm/emulate.c:3679:9: note: Calling 'load_segment_descriptor'
            return load_segment_descriptor(ctxt, sel, ctxt->modrm_reg);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1727:6: note: 'seg' is not equal to VCPU_SREG_SS
            if (seg == VCPU_SREG_SS && selector == 3 &&
                ^~~
    arch/x86/kvm/emulate.c:1727:26: note: Left side of '&&' is false
            if (seg == VCPU_SREG_SS && selector == 3 &&
                                    ^
    arch/x86/kvm/emulate.c:1731:9: note: Calling '__load_segment_descriptor'
            return __load_segment_descriptor(ctxt, selector, seg, cpl,
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1547:23: note: Assuming the condition is false
            bool null_selector = !(selector & ~0x3); /* 0000-0003 are 
null */
                                 ^~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1548:2: note: 'desc_addr' declared without an 
initial value
            ulong desc_addr;
            ^~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1555:6: note: Assuming field 'mode' is not 
equal to X86EMUL_MODE_REAL
            if (ctxt->mode == X86EMUL_MODE_REAL) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1555:2: note: Taking false branch
            if (ctxt->mode == X86EMUL_MODE_REAL) {
            ^
    arch/x86/kvm/emulate.c:1561:13: note: 'seg' is <= VCPU_SREG_GS
            } else if (seg <= VCPU_SREG_GS && ctxt->mode == 
X86EMUL_MODE_VM86) {
                       ^~~
    arch/x86/kvm/emulate.c:1561:13: note: Left side of '&&' is true
    arch/x86/kvm/emulate.c:1561:36: note: Assuming field 'mode' is not 
equal to X86EMUL_MODE_VM86
            } else if (seg <= VCPU_SREG_GS && ctxt->mode == 
X86EMUL_MODE_VM86) {
 
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1561:9: note: Taking false branch
            } else if (seg <= VCPU_SREG_GS && ctxt->mode == 
X86EMUL_MODE_VM86) {
                   ^
    arch/x86/kvm/emulate.c:1575:6: note: 'seg' is not equal to VCPU_SREG_TR
            if (seg == VCPU_SREG_TR && (selector & (1 << 2)))
                ^~~
    arch/x86/kvm/emulate.c:1575:26: note: Left side of '&&' is false
            if (seg == VCPU_SREG_TR && (selector & (1 << 2)))
                                    ^
    arch/x86/kvm/emulate.c:1579:6: note: 'null_selector' is false
            if (null_selector) {
                ^~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1579:2: note: Taking false branch
            if (null_selector) {
            ^
    arch/x86/kvm/emulate.c:1603:8: note: Calling 'read_segment_descriptor'
            ret = read_segment_descriptor(ctxt, selector, &seg_desc, 
&desc_addr);
 
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1517:7: note: Calling 'get_descriptor_ptr'
            rc = get_descriptor_ptr(ctxt, selector, desc_addr_p);
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1491:6: note: Assuming the condition is true
            if (dt.size < index * 8 + 7)
                ^~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1491:2: note: Taking true branch
            if (dt.size < index * 8 + 7)
            ^
    arch/x86/kvm/emulate.c:1517:7: note: Returning from 'get_descriptor_ptr'
            rc = get_descriptor_ptr(ctxt, selector, desc_addr_p);
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1518:6: note: Assuming 'rc' is equal to 
X86EMUL_CONTINUE
            if (rc != X86EMUL_CONTINUE)
                ^~~~~~~~~~~~~~~~~~~~~~
    arch/x86/kvm/emulate.c:1518:2: note: Taking false branch
            if (rc != X86EMUL_CONTINUE)
            ^

vim +/remain +139 arch/x86/kvm/../../../virt/kvm/binary_stats.c

cb082bfab59a224 Jing Zhang 2021-06-18   12  cb082bfab59a224 Jing Zhang 
2021-06-18   13  /**
cb082bfab59a224 Jing Zhang 2021-06-18   14   * kvm_stats_read() - Common 
function to read from the binary statistics
cb082bfab59a224 Jing Zhang 2021-06-18   15   * file descriptor.
cb082bfab59a224 Jing Zhang 2021-06-18   16   *
cb082bfab59a224 Jing Zhang 2021-06-18   17   * @id: identification 
string of the stats
cb082bfab59a224 Jing Zhang 2021-06-18   18   * @header: stats header for 
a vm or a vcpu
cb082bfab59a224 Jing Zhang 2021-06-18   19   * @desc: start address of 
an array of stats descriptors for a vm or a vcpu
cb082bfab59a224 Jing Zhang 2021-06-18   20   * @stats: start address of 
stats data block for a vm or a vcpu
cb082bfab59a224 Jing Zhang 2021-06-18   21   * @size_stats: the size of 
stats data block pointed by @stats
cb082bfab59a224 Jing Zhang 2021-06-18   22   * @user_buffer: start 
address of userspace buffer
cb082bfab59a224 Jing Zhang 2021-06-18   23   * @size: requested read 
size from userspace
cb082bfab59a224 Jing Zhang 2021-06-18   24   * @offset: the start 
position from which the content will be read for the
cb082bfab59a224 Jing Zhang 2021-06-18   25   *          corresponding vm 
or vcp file descriptor
cb082bfab59a224 Jing Zhang 2021-06-18   26   *
cb082bfab59a224 Jing Zhang 2021-06-18   27   * The file content of a 
vm/vcpu file descriptor is now defined as below:
cb082bfab59a224 Jing Zhang 2021-06-18   28   * +-------------+
cb082bfab59a224 Jing Zhang 2021-06-18   29   * |   Header    |
cb082bfab59a224 Jing Zhang 2021-06-18   30   * +-------------+
cb082bfab59a224 Jing Zhang 2021-06-18   31   * |  id string  |
cb082bfab59a224 Jing Zhang 2021-06-18   32   * +-------------+
cb082bfab59a224 Jing Zhang 2021-06-18   33   * | Descriptors |
cb082bfab59a224 Jing Zhang 2021-06-18   34   * +-------------+
cb082bfab59a224 Jing Zhang 2021-06-18   35   * | Stats Data  |
cb082bfab59a224 Jing Zhang 2021-06-18   36   * +-------------+
cb082bfab59a224 Jing Zhang 2021-06-18   37   * Although this function 
allows userspace to read any amount of data (as long
cb082bfab59a224 Jing Zhang 2021-06-18   38   * as in the limit) from any 
position, the typical usage would follow below
cb082bfab59a224 Jing Zhang 2021-06-18   39   * steps:
cb082bfab59a224 Jing Zhang 2021-06-18   40   * 1. Read header from 
offset 0. Get the offset of descriptors and stats data
cb082bfab59a224 Jing Zhang 2021-06-18   41   *    and some other 
necessary information. This is a one-time work for the
cb082bfab59a224 Jing Zhang 2021-06-18   42   *    lifecycle of the 
corresponding vm/vcpu stats fd.
cb082bfab59a224 Jing Zhang 2021-06-18   43   * 2. Read id string from 
its offset. This is a one-time work for the lifecycle
cb082bfab59a224 Jing Zhang 2021-06-18   44   *    of the corresponding 
vm/vcpu stats fd.
cb082bfab59a224 Jing Zhang 2021-06-18   45   * 3. Read descriptors from 
its offset and discover all the stats by parsing
cb082bfab59a224 Jing Zhang 2021-06-18   46   *    descriptors. This is a 
one-time work for the lifecycle of the
cb082bfab59a224 Jing Zhang 2021-06-18   47   *    corresponding vm/vcpu 
stats fd.
cb082bfab59a224 Jing Zhang 2021-06-18   48   * 4. Periodically read 
stats data from its offset using pread.
cb082bfab59a224 Jing Zhang 2021-06-18   49   *
cb082bfab59a224 Jing Zhang 2021-06-18   50   * Return: the number of 
bytes that has been successfully read
cb082bfab59a224 Jing Zhang 2021-06-18   51   */
cb082bfab59a224 Jing Zhang 2021-06-18   52  ssize_t kvm_stats_read(char 
*id, const struct kvm_stats_header *header,
cb082bfab59a224 Jing Zhang 2021-06-18   53  		       const struct 
_kvm_stats_desc *desc,
cb082bfab59a224 Jing Zhang 2021-06-18   54  		       void *stats, size_t 
size_stats,
cb082bfab59a224 Jing Zhang 2021-06-18   55  		       char __user 
*user_buffer, size_t size, loff_t *offset)
cb082bfab59a224 Jing Zhang 2021-06-18   56  {
cb082bfab59a224 Jing Zhang 2021-06-18   57  	ssize_t len;
cb082bfab59a224 Jing Zhang 2021-06-18   58  	ssize_t copylen;
cb082bfab59a224 Jing Zhang 2021-06-18   59  	ssize_t remain = size;
cb082bfab59a224 Jing Zhang 2021-06-18   60  	size_t size_desc;
cb082bfab59a224 Jing Zhang 2021-06-18   61  	size_t size_header;
cb082bfab59a224 Jing Zhang 2021-06-18   62  	void *src;
cb082bfab59a224 Jing Zhang 2021-06-18   63  	loff_t pos = *offset;
cb082bfab59a224 Jing Zhang 2021-06-18   64  	char __user *dest = 
user_buffer;
cb082bfab59a224 Jing Zhang 2021-06-18   65  cb082bfab59a224 Jing Zhang 
2021-06-18   66  	size_header = sizeof(*header);
cb082bfab59a224 Jing Zhang 2021-06-18   67  	size_desc = 
header->num_desc * sizeof(*desc);
cb082bfab59a224 Jing Zhang 2021-06-18   68  cb082bfab59a224 Jing Zhang 
2021-06-18   69  	len = KVM_STATS_NAME_SIZE + size_header + size_desc + 
size_stats - pos;
cb082bfab59a224 Jing Zhang 2021-06-18   70  	len = min(len, remain);
cb082bfab59a224 Jing Zhang 2021-06-18   71  	if (len <= 0)
cb082bfab59a224 Jing Zhang 2021-06-18   72  		return 0;
cb082bfab59a224 Jing Zhang 2021-06-18   73  	remain = len;
cb082bfab59a224 Jing Zhang 2021-06-18   74  cb082bfab59a224 Jing Zhang 
2021-06-18   75  	/*
cb082bfab59a224 Jing Zhang 2021-06-18   76  	 * Copy kvm stats header.
cb082bfab59a224 Jing Zhang 2021-06-18   77  	 * The header is the first 
block of content userspace usually read out.
cb082bfab59a224 Jing Zhang 2021-06-18   78  	 * The pos is 0 and the 
copylen and remain would be the size of header.
cb082bfab59a224 Jing Zhang 2021-06-18   79  	 * The copy of the header 
would be skipped if offset is larger than the
cb082bfab59a224 Jing Zhang 2021-06-18   80  	 * size of header. That 
usually happens when userspace reads stats
cb082bfab59a224 Jing Zhang 2021-06-18   81  	 * descriptors and stats data.
cb082bfab59a224 Jing Zhang 2021-06-18   82  	 */
cb082bfab59a224 Jing Zhang 2021-06-18   83  	copylen = size_header - pos;
cb082bfab59a224 Jing Zhang 2021-06-18   84  	copylen = min(copylen, remain);
cb082bfab59a224 Jing Zhang 2021-06-18   85  	if (copylen > 0) {
cb082bfab59a224 Jing Zhang 2021-06-18   86  		src = (void *)header + pos;
cb082bfab59a224 Jing Zhang 2021-06-18   87  		if (copy_to_user(dest, 
src, copylen))
cb082bfab59a224 Jing Zhang 2021-06-18   88  			return -EFAULT;
cb082bfab59a224 Jing Zhang 2021-06-18   89  		remain -= copylen;
cb082bfab59a224 Jing Zhang 2021-06-18   90  		pos += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18   91  		dest += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18   92  	}
cb082bfab59a224 Jing Zhang 2021-06-18   93  cb082bfab59a224 Jing Zhang 
2021-06-18   94  	/*
cb082bfab59a224 Jing Zhang 2021-06-18   95  	 * Copy kvm stats header id 
string.
cb082bfab59a224 Jing Zhang 2021-06-18   96  	 * The id string is unique 
for every vm/vcpu, which is stored in kvm
cb082bfab59a224 Jing Zhang 2021-06-18   97  	 * and kvm_vcpu structure.
cb082bfab59a224 Jing Zhang 2021-06-18   98  	 * The id string is part of 
the stat header from the perspective of
cb082bfab59a224 Jing Zhang 2021-06-18   99  	 * userspace, it is usually 
read out together with previous constant
cb082bfab59a224 Jing Zhang 2021-06-18  100  	 * header part and could be 
skipped for later descriptors and stats
cb082bfab59a224 Jing Zhang 2021-06-18  101  	 * data readings.
cb082bfab59a224 Jing Zhang 2021-06-18  102  	 */
cb082bfab59a224 Jing Zhang 2021-06-18  103  	copylen = header->id_offset 
+ KVM_STATS_NAME_SIZE - pos;
cb082bfab59a224 Jing Zhang 2021-06-18  104  	copylen = min(copylen, remain);
cb082bfab59a224 Jing Zhang 2021-06-18  105  	if (copylen > 0) {
cb082bfab59a224 Jing Zhang 2021-06-18  106  		src = id + pos - 
header->id_offset;
cb082bfab59a224 Jing Zhang 2021-06-18  107  		if (copy_to_user(dest, 
src, copylen))
cb082bfab59a224 Jing Zhang 2021-06-18  108  			return -EFAULT;
cb082bfab59a224 Jing Zhang 2021-06-18  109  		remain -= copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  110  		pos += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  111  		dest += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  112  	}
cb082bfab59a224 Jing Zhang 2021-06-18  113  cb082bfab59a224 Jing Zhang 
2021-06-18  114  	/*
cb082bfab59a224 Jing Zhang 2021-06-18  115  	 * Copy kvm stats descriptors.
cb082bfab59a224 Jing Zhang 2021-06-18  116  	 * The descriptors copy 
would be skipped in the typical case that
cb082bfab59a224 Jing Zhang 2021-06-18  117  	 * userspace periodically 
read stats data, since the pos would be
cb082bfab59a224 Jing Zhang 2021-06-18  118  	 * greater than the end 
address of descriptors
cb082bfab59a224 Jing Zhang 2021-06-18  119  	 * 
(header->header.desc_offset + size_desc) causing copylen <= 0.
cb082bfab59a224 Jing Zhang 2021-06-18  120  	 */
cb082bfab59a224 Jing Zhang 2021-06-18  121  	copylen = 
header->desc_offset + size_desc - pos;
cb082bfab59a224 Jing Zhang 2021-06-18  122  	copylen = min(copylen, remain);
cb082bfab59a224 Jing Zhang 2021-06-18  123  	if (copylen > 0) {
cb082bfab59a224 Jing Zhang 2021-06-18  124  		src = (void *)desc + pos - 
header->desc_offset;
cb082bfab59a224 Jing Zhang 2021-06-18  125  		if (copy_to_user(dest, 
src, copylen))
cb082bfab59a224 Jing Zhang 2021-06-18  126  			return -EFAULT;
cb082bfab59a224 Jing Zhang 2021-06-18  127  		remain -= copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  128  		pos += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  129  		dest += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  130  	}
cb082bfab59a224 Jing Zhang 2021-06-18  131  cb082bfab59a224 Jing Zhang 
2021-06-18  132  	/* Copy kvm stats values */
cb082bfab59a224 Jing Zhang 2021-06-18  133  	copylen = 
header->data_offset + size_stats - pos;
cb082bfab59a224 Jing Zhang 2021-06-18  134  	copylen = min(copylen, remain);
cb082bfab59a224 Jing Zhang 2021-06-18  135  	if (copylen > 0) {
cb082bfab59a224 Jing Zhang 2021-06-18  136  		src = stats + pos - 
header->data_offset;
cb082bfab59a224 Jing Zhang 2021-06-18  137  		if (copy_to_user(dest, 
src, copylen))
cb082bfab59a224 Jing Zhang 2021-06-18  138  			return -EFAULT;
cb082bfab59a224 Jing Zhang 2021-06-18 @139  		remain -= copylen;
cb082bfab59a224 Jing Zhang 2021-06-18  140  		pos += copylen;
cb082bfab59a224 Jing Zhang 2021-06-18 @141  		dest += copylen;

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

2022

2021

2020

2019

[kbuild-all] arch/x86/kvm/../../../virt/kvm/binary_stats.c:139:3: warning: Value stored to 'remain' is never read [clang-analyzer-deadcode.DeadStores]