2016-11-30 18:51:23

by Dan Carpenter

Subject: [bug report] perf jit: add source line info support

Hello Stephane Eranian,

The patch 598b7c6919c7: "perf jit: add source line info support" from
Nov 30, 2015, leads to the following static checker warning:

./tools/perf/util/genelf_debug.c:211 emit_signed_LEB128()
warn: potential left shift more than type allows '57'

./tools/perf/util/genelf_debug.c
202 static void emit_signed_LEB128(struct buffer_ext *be, long data)
203 {
204 int more = 1;
205 int negative = data < 0;
206 int size = sizeof(long) * CHAR_BIT;
207 while (more) {
208 ubyte cur = data & 0x7F;
209 data >>= 7;
210 if (negative)
211 data |= - (1 << (size - 7));
^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is a no-op on 64 bit systems. I suspect it's not intentional?

212 if ((data == 0 && !(cur & 0x40)) ||
213 (data == -1l && (cur & 0x40)))
214 more = 0;
215 else
216 cur |= 0x80;
217 buffer_ext_add(be, &cur, 1);
218 }
219 }

regards,
dan carpenter

2016-12-10 05:16:44

by Stephane Eranian

Subject: Re: [bug report] perf jit: add source line info support

Hi Dan,

On Wed, Nov 30, 2016 at 10:48 AM, Dan Carpenter
<[email protected]> wrote:
> Hello Stephane Eranian,
>
> The patch 598b7c6919c7: "perf jit: add source line info support" from
> Nov 30, 2015, leads to the following static checker warning:
>
> ./tools/perf/util/genelf_debug.c:211 emit_signed_LEB128()
> warn: potential left shift more than type allows '57'
>
> ./tools/perf/util/genelf_debug.c
> 202 static void emit_signed_LEB128(struct buffer_ext *be, long data)
> 203 {
> 204 int more = 1;
> 205 int negative = data < 0;
> 206 int size = sizeof(long) * CHAR_BIT;
> 207 while (more) {
> 208 ubyte cur = data & 0x7F;
> 209 data >>= 7;
> 210 if (negative)
> 211 data |= - (1 << (size - 7));
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This is a no-op on 64 bit systems. I suspect it's not intentional?
>
I suspect size should be: size = sizeof(int) * CHAR_BIT;
I will test that.

> 212 if ((data == 0 && !(cur & 0x40)) ||
> 213 (data == -1l && (cur & 0x40)))
> 214 more = 0;
> 215 else
> 216 cur |= 0x80;
> 217 buffer_ext_add(be, &cur, 1);
> 218 }
> 219 }
>
> regards,
> dan carpenter

2016-12-10 05:23:31

by Stephane Eranian

Subject: Re: [bug report] perf jit: add source line info support

On Fri, Dec 9, 2016 at 9:16 PM, Stephane Eranian <[email protected]> wrote:
> Hi Dan,
>
> On Wed, Nov 30, 2016 at 10:48 AM, Dan Carpenter
> <[email protected]> wrote:
>> Hello Stephane Eranian,
>>
>> The patch 598b7c6919c7: "perf jit: add source line info support" from
>> Nov 30, 2015, leads to the following static checker warning:
>>
>> ./tools/perf/util/genelf_debug.c:211 emit_signed_LEB128()
>> warn: potential left shift more than type allows '57'
>>
>> ./tools/perf/util/genelf_debug.c
>> 202 static void emit_signed_LEB128(struct buffer_ext *be, long data)
>> 203 {
>> 204 int more = 1;
>> 205 int negative = data < 0;
>> 206 int size = sizeof(long) * CHAR_BIT;
>> 207 while (more) {
>> 208 ubyte cur = data & 0x7F;
>> 209 data >>= 7;
>> 210 if (negative)
>> 211 data |= - (1 << (size - 7));
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> This is a no-op on 64 bit systems. I suspect it's not intentional?
>>
> I suspect size should be: size = sizeof(int) * CHAR_BIT;
> I will test that.
Sorry, I think the issue is on the 1 shift, should be 1UL instead.
>
>> 212 if ((data == 0 && !(cur & 0x40)) ||
>> 213 (data == -1l && (cur & 0x40)))
>> 214 more = 0;
>> 215 else
>> 216 cur |= 0x80;
>> 217 buffer_ext_add(be, &cur, 1);
>> 218 }
>> 219 }
>>
>> regards,
>> dan carpenter