[1/3] btf: add 'extern' linkage for variables [PR106773]
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Commit Message
Add support for the 'extern' linkage value for BTF_KIND_VAR records,
which is used for variables declared as extern in the source file.
PR target/106773
gcc/
* btfout.cc (BTF_LINKAGE_STATIC): New define.
(BTF_LINKAGE_GLOBAL): Likewise.
(BTF_LINKAGE_EXTERN): Likewise.
(btf_collect_datasec): Mark extern variables as such.
(btf_asm_varent): Accomodate 'extern' linkage.
gcc/testsuite/
* gcc.dg/debug/btf/btf-variables-4.c: New test.
include/
* btf.h (struct btf_var): Update comment to note 'extern' linkage.
---
gcc/btfout.cc | 9 ++++++-
.../gcc.dg/debug/btf/btf-variables-4.c | 24 +++++++++++++++++++
include/btf.h | 2 +-
3 files changed, 33 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
Comments
Hi David,
On 12/7/22 12:57, David Faust wrote:
> Add support for the 'extern' linkage value for BTF_KIND_VAR records,
> which is used for variables declared as extern in the source file.
>
> PR target/106773
>
> gcc/
>
> * btfout.cc (BTF_LINKAGE_STATIC): New define.
> (BTF_LINKAGE_GLOBAL): Likewise.
> (BTF_LINKAGE_EXTERN): Likewise.
> (btf_collect_datasec): Mark extern variables as such.
> (btf_asm_varent): Accomodate 'extern' linkage.
>
> gcc/testsuite/
>
> * gcc.dg/debug/btf/btf-variables-4.c: New test.
>
> include/
>
> * btf.h (struct btf_var): Update comment to note 'extern' linkage.
> ---
> gcc/btfout.cc | 9 ++++++-
> .../gcc.dg/debug/btf/btf-variables-4.c | 24 +++++++++++++++++++
> include/btf.h | 2 +-
> 3 files changed, 33 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>
> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
> index aef9fd70a28..a1c6266a7db 100644
> --- a/gcc/btfout.cc
> +++ b/gcc/btfout.cc
> @@ -66,6 +66,10 @@ static char btf_info_section_label[MAX_BTF_LABEL_BYTES];
>
> #define BTF_INVALID_TYPEID 0xFFFFFFFF
>
> +#define BTF_LINKAGE_STATIC 0
> +#define BTF_LINKAGE_GLOBAL 1
> +#define BTF_LINKAGE_EXTERN 2
> +
I was about to suggest to rename these to use the same name as used in
the kernel btf.h. What is used there is:
BTF_VAR_STATIC = 0,
BTF_VAR_GLOBAL_ALLOCATED = 1,
BTF_VAR_GLOBAL_EXTERN = 2,
But after looking at the Patch 3/3, I see you reuse these definitions
for functions as well. I just find the names confusing on the first look
- "BTF_LINKAGE_STATIC".
Naming aside, what do you think about adding the defines to
include/btf.h instead ?
> /* Mapping of CTF variables to the IDs they will be assigned when they are
> converted to BTF_KIND_VAR type records. Strictly accounts for the index
> from the start of the variable type entries, does not include the number
> @@ -314,6 +318,9 @@ btf_collect_datasec (ctf_container_ref ctfc)
> continue;
>
> const char *section_name = node->get_section ();
> + /* Mark extern variables. */
> + if (DECL_EXTERNAL (node->decl))
> + dvd->dvd_visibility = BTF_LINKAGE_EXTERN;
>
This made me think about the following case.
extern const char a[];
const char a[] = "foo";
What is the expected BTF for this? Since BTF can differentiate between
the non-defining extern variable declaration, I expected to see two
variables with different "linkage". At this time I see, two variables
with global linkage but different types:
.long 0xe000000 # btv_info
.long 0x4 # btv_type
.long 0x1 # btv_linkage
.long 0x1f # btv_name
.long 0xe000000 # btv_info
.long 0x7 # btv_type
.long 0x1 # btv_linkage
.long 0x60 # btt_name
> if (section_name == NULL)
> {
> @@ -676,7 +683,7 @@ btf_asm_varent (ctf_dvdef_ref var)
> dw2_asm_output_data (4, var->dvd_name_offset, "btv_name");
> dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_VAR, 0, 0), "btv_info");
> dw2_asm_output_data (4, get_btf_id (var->dvd_type), "btv_type");
> - dw2_asm_output_data (4, (var->dvd_visibility ? 1 : 0), "btv_linkage");
> + dw2_asm_output_data (4, var->dvd_visibility, "btv_linkage");
> }
>
> /* Asm'out a member description following a BTF_KIND_STRUCT or
> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
> new file mode 100644
> index 00000000000..d77600bae1c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
> @@ -0,0 +1,24 @@
> +/* Test BTF generation for extern variables. */
> +
> +/* { dg-do compile } */
> +/* { dg-options "-O0 -gbtf -dA" } */
> +
> +/* Expect 4 variables. */
> +/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 4 } } */
> +
> +/* 2 extern, 1 global, 1 static. */
> +/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*btv_linkage" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \]0x2\[\t \]+\[^\n\]*btv_linkage" 2 } } */
> +
> +extern int a;
> +extern const int b;
> +int c;
> +static const int d = 5;
> +
> +int foo (int x)
> +{
> + c = a + b + x;
> +
> + return c + d;
> +}
> diff --git a/include/btf.h b/include/btf.h
> index eba67f9d599..9a757ce5bc9 100644
> --- a/include/btf.h
> +++ b/include/btf.h
> @@ -182,7 +182,7 @@ struct btf_param
> information about the variable. */
> struct btf_var
> {
> - uint32_t linkage; /* Currently only 0=static or 1=global. */
> + uint32_t linkage; /* 0=static, 1=global, 2=extern. */
> };
>
> /* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
On 12/8/22 22:55, Indu Bhagat wrote:
> Hi David,
>
> On 12/7/22 12:57, David Faust wrote:
>> Add support for the 'extern' linkage value for BTF_KIND_VAR records,
>> which is used for variables declared as extern in the source file.
>>
>> PR target/106773
>>
>> gcc/
>>
>> * btfout.cc (BTF_LINKAGE_STATIC): New define.
>> (BTF_LINKAGE_GLOBAL): Likewise.
>> (BTF_LINKAGE_EXTERN): Likewise.
>> (btf_collect_datasec): Mark extern variables as such.
>> (btf_asm_varent): Accomodate 'extern' linkage.
>>
>> gcc/testsuite/
>>
>> * gcc.dg/debug/btf/btf-variables-4.c: New test.
>>
>> include/
>>
>> * btf.h (struct btf_var): Update comment to note 'extern' linkage.
>> ---
>> gcc/btfout.cc | 9 ++++++-
>> .../gcc.dg/debug/btf/btf-variables-4.c | 24 +++++++++++++++++++
>> include/btf.h | 2 +-
>> 3 files changed, 33 insertions(+), 2 deletions(-)
>> create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>>
>> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
>> index aef9fd70a28..a1c6266a7db 100644
>> --- a/gcc/btfout.cc
>> +++ b/gcc/btfout.cc
>> @@ -66,6 +66,10 @@ static char btf_info_section_label[MAX_BTF_LABEL_BYTES];
>>
>> #define BTF_INVALID_TYPEID 0xFFFFFFFF
>>
>> +#define BTF_LINKAGE_STATIC 0
>> +#define BTF_LINKAGE_GLOBAL 1
>> +#define BTF_LINKAGE_EXTERN 2
>> +
>
> I was about to suggest to rename these to use the same name as used in
> the kernel btf.h. What is used there is:
> BTF_VAR_STATIC = 0,
> BTF_VAR_GLOBAL_ALLOCATED = 1,
> BTF_VAR_GLOBAL_EXTERN = 2,
>
> But after looking at the Patch 3/3, I see you reuse these definitions
> for functions as well. I just find the names confusing on the first look
> - "BTF_LINKAGE_STATIC".
>
> Naming aside, what do you think about adding the defines to
> include/btf.h instead ?
Actually, I forgot these are defined (separately for both VARs and FUNCs)
in the kernel uapi/linux/btf.h. It would probably be best to mirror that
approach and use a separate enum for each, in include/btf.h. WDYT?
>
>> /* Mapping of CTF variables to the IDs they will be assigned when they are
>> converted to BTF_KIND_VAR type records. Strictly accounts for the index
>> from the start of the variable type entries, does not include the number
>> @@ -314,6 +318,9 @@ btf_collect_datasec (ctf_container_ref ctfc)
>> continue;
>>
>> const char *section_name = node->get_section ();
>> + /* Mark extern variables. */
>> + if (DECL_EXTERNAL (node->decl))
>> + dvd->dvd_visibility = BTF_LINKAGE_EXTERN;
>>
>
> This made me think about the following case.
>
> extern const char a[];
> const char a[] = "foo";
>
> What is the expected BTF for this? Since BTF can differentiate between
> the non-defining extern variable declaration, I expected to see two
> variables with different "linkage". At this time I see, two variables
> with global linkage but different types:
>
> .long 0xe000000 # btv_info
> .long 0x4 # btv_type
> .long 0x1 # btv_linkage
> .long 0x1f # btv_name
> .long 0xe000000 # btv_info
> .long 0x7 # btv_type
> .long 0x1 # btv_linkage
> .long 0x60 # btt_name
>
The BTF documentation in the kernel does not clarify this case.
Going off the implementation in clang as a reference, it looks like
only one VAR record is expected, with 'global' linkage:
$ cat extdef.c
extern const char a[];
const char a[] = "foo";
$ clang -target bpf -c -g extdef.c -o extdef.o
$ /usr/sbin/bpftool btf dump file extdef.o
[1] CONST '(anon)' type_id=2
[2] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
[3] ARRAY '(anon)' type_id=1 index_type_id=4 nr_elems=4
[4] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
[5] VAR 'a' type_id=3, linkage=global
[6] DATASEC '.rodata' size=0 vlen=1
type_id=5 offset=0 size=4 (VAR 'a')
In GCC we have two records since we have two DIEs for "a" in the
DWARF. One has type "const char[4]" and the other has type
"const char[]", so the BTF records point to two different types
as well.
I guess we should find a way in BTF to identify this and
emit only the defining definition as clang does.
>> if (section_name == NULL)
>> {
>> @@ -676,7 +683,7 @@ btf_asm_varent (ctf_dvdef_ref var)
>> dw2_asm_output_data (4, var->dvd_name_offset, "btv_name");
>> dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_VAR, 0, 0), "btv_info");
>> dw2_asm_output_data (4, get_btf_id (var->dvd_type), "btv_type");
>> - dw2_asm_output_data (4, (var->dvd_visibility ? 1 : 0), "btv_linkage");
>> + dw2_asm_output_data (4, var->dvd_visibility, "btv_linkage");
>> }
>>
>> /* Asm'out a member description following a BTF_KIND_STRUCT or
>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>> new file mode 100644
>> index 00000000000..d77600bae1c
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>> @@ -0,0 +1,24 @@
>> +/* Test BTF generation for extern variables. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O0 -gbtf -dA" } */
>> +
>> +/* Expect 4 variables. */
>> +/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 4 } } */
>> +
>> +/* 2 extern, 1 global, 1 static. */
>> +/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*btv_linkage" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
>> +/* { dg-final { scan-assembler-times "\[\t \]0x2\[\t \]+\[^\n\]*btv_linkage" 2 } } */
>> +
>> +extern int a;
>> +extern const int b;
>> +int c;
>> +static const int d = 5;
>> +
>> +int foo (int x)
>> +{
>> + c = a + b + x;
>> +
>> + return c + d;
>> +}
>> diff --git a/include/btf.h b/include/btf.h
>> index eba67f9d599..9a757ce5bc9 100644
>> --- a/include/btf.h
>> +++ b/include/btf.h
>> @@ -182,7 +182,7 @@ struct btf_param
>> information about the variable. */
>> struct btf_var
>> {
>> - uint32_t linkage; /* Currently only 0=static or 1=global. */
>> + uint32_t linkage; /* 0=static, 1=global, 2=extern. */
>> };
>>
>> /* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
>
On 12/12/22 12:47, David Faust wrote:
>
>
> On 12/8/22 22:55, Indu Bhagat wrote:
>> Hi David,
>>
>> On 12/7/22 12:57, David Faust wrote:
>>> Add support for the 'extern' linkage value for BTF_KIND_VAR records,
>>> which is used for variables declared as extern in the source file.
>>>
>>> PR target/106773
>>>
>>> gcc/
>>>
>>> * btfout.cc (BTF_LINKAGE_STATIC): New define.
>>> (BTF_LINKAGE_GLOBAL): Likewise.
>>> (BTF_LINKAGE_EXTERN): Likewise.
>>> (btf_collect_datasec): Mark extern variables as such.
>>> (btf_asm_varent): Accomodate 'extern' linkage.
>>>
>>> gcc/testsuite/
>>>
>>> * gcc.dg/debug/btf/btf-variables-4.c: New test.
>>>
>>> include/
>>>
>>> * btf.h (struct btf_var): Update comment to note 'extern' linkage.
>>> ---
>>> gcc/btfout.cc | 9 ++++++-
>>> .../gcc.dg/debug/btf/btf-variables-4.c | 24 +++++++++++++++++++
>>> include/btf.h | 2 +-
>>> 3 files changed, 33 insertions(+), 2 deletions(-)
>>> create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>>>
>>> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
>>> index aef9fd70a28..a1c6266a7db 100644
>>> --- a/gcc/btfout.cc
>>> +++ b/gcc/btfout.cc
>>> @@ -66,6 +66,10 @@ static char btf_info_section_label[MAX_BTF_LABEL_BYTES];
>>>
>>> #define BTF_INVALID_TYPEID 0xFFFFFFFF
>>>
>>> +#define BTF_LINKAGE_STATIC 0
>>> +#define BTF_LINKAGE_GLOBAL 1
>>> +#define BTF_LINKAGE_EXTERN 2
>>> +
>>
>> I was about to suggest to rename these to use the same name as used in
>> the kernel btf.h. What is used there is:
>> BTF_VAR_STATIC = 0,
>> BTF_VAR_GLOBAL_ALLOCATED = 1,
>> BTF_VAR_GLOBAL_EXTERN = 2,
>>
>> But after looking at the Patch 3/3, I see you reuse these definitions
>> for functions as well. I just find the names confusing on the first look
>> - "BTF_LINKAGE_STATIC".
>>
>> Naming aside, what do you think about adding the defines to
>> include/btf.h instead ?
>
> Actually, I forgot these are defined (separately for both VARs and FUNCs)
> in the kernel uapi/linux/btf.h. It would probably be best to mirror that
> approach and use a separate enum for each, in include/btf.h. WDYT?
>
Yes, mirroring in include/btf.h sounds good.
>>
>>> /* Mapping of CTF variables to the IDs they will be assigned when they are
>>> converted to BTF_KIND_VAR type records. Strictly accounts for the index
>>> from the start of the variable type entries, does not include the number
>>> @@ -314,6 +318,9 @@ btf_collect_datasec (ctf_container_ref ctfc)
>>> continue;
>>>
>>> const char *section_name = node->get_section ();
>>> + /* Mark extern variables. */
>>> + if (DECL_EXTERNAL (node->decl))
>>> + dvd->dvd_visibility = BTF_LINKAGE_EXTERN;
>>>
>>
>> This made me think about the following case.
>>
>> extern const char a[];
>> const char a[] = "foo";
>>
>> What is the expected BTF for this? Since BTF can differentiate between
>> the non-defining extern variable declaration, I expected to see two
>> variables with different "linkage". At this time I see, two variables
>> with global linkage but different types:
>>
>> .long 0xe000000 # btv_info
>> .long 0x4 # btv_type
>> .long 0x1 # btv_linkage
>> .long 0x1f # btv_name
>> .long 0xe000000 # btv_info
>> .long 0x7 # btv_type
>> .long 0x1 # btv_linkage
>> .long 0x60 # btt_name
>>
>
> The BTF documentation in the kernel does not clarify this case.
> Going off the implementation in clang as a reference, it looks like
> only one VAR record is expected, with 'global' linkage:
>
> $ cat extdef.c
> extern const char a[];
> const char a[] = "foo";
>
> $ clang -target bpf -c -g extdef.c -o extdef.o
>
> $ /usr/sbin/bpftool btf dump file extdef.o
> [1] CONST '(anon)' type_id=2
> [2] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
> [3] ARRAY '(anon)' type_id=1 index_type_id=4 nr_elems=4
> [4] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
> [5] VAR 'a' type_id=3, linkage=global
> [6] DATASEC '.rodata' size=0 vlen=1
> type_id=5 offset=0 size=4 (VAR 'a')
>
> In GCC we have two records since we have two DIEs for "a" in the
> DWARF. One has type "const char[4]" and the other has type
> "const char[]", so the BTF records point to two different types
> as well.
>
> I guess we should find a way in BTF to identify this and
> emit only the defining definition as clang does.
>
>
CTF had a similar issue earlier. See PR105089.
https://gcc.gnu.org/PR105089
>>> if (section_name == NULL)
>>> {
>>> @@ -676,7 +683,7 @@ btf_asm_varent (ctf_dvdef_ref var)
>>> dw2_asm_output_data (4, var->dvd_name_offset, "btv_name");
>>> dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_VAR, 0, 0), "btv_info");
>>> dw2_asm_output_data (4, get_btf_id (var->dvd_type), "btv_type");
>>> - dw2_asm_output_data (4, (var->dvd_visibility ? 1 : 0), "btv_linkage");
>>> + dw2_asm_output_data (4, var->dvd_visibility, "btv_linkage");
>>> }
>>>
>>> /* Asm'out a member description following a BTF_KIND_STRUCT or
>>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>>> new file mode 100644
>>> index 00000000000..d77600bae1c
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-variables-4.c
>>> @@ -0,0 +1,24 @@
>>> +/* Test BTF generation for extern variables. */
>>> +
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O0 -gbtf -dA" } */
>>> +
>>> +/* Expect 4 variables. */
>>> +/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 4 } } */
>>> +
>>> +/* 2 extern, 1 global, 1 static. */
>>> +/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*btv_linkage" 1 } } */
>>> +/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
>>> +/* { dg-final { scan-assembler-times "\[\t \]0x2\[\t \]+\[^\n\]*btv_linkage" 2 } } */
>>> +
>>> +extern int a;
>>> +extern const int b;
>>> +int c;
>>> +static const int d = 5;
>>> +
>>> +int foo (int x)
>>> +{
>>> + c = a + b + x;
>>> +
>>> + return c + d;
>>> +}
>>> diff --git a/include/btf.h b/include/btf.h
>>> index eba67f9d599..9a757ce5bc9 100644
>>> --- a/include/btf.h
>>> +++ b/include/btf.h
>>> @@ -182,7 +182,7 @@ struct btf_param
>>> information about the variable. */
>>> struct btf_var
>>> {
>>> - uint32_t linkage; /* Currently only 0=static or 1=global. */
>>> + uint32_t linkage; /* 0=static, 1=global, 2=extern. */
>>> };
>>>
>>> /* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
>>
@@ -66,6 +66,10 @@ static char btf_info_section_label[MAX_BTF_LABEL_BYTES];
#define BTF_INVALID_TYPEID 0xFFFFFFFF
+#define BTF_LINKAGE_STATIC 0
+#define BTF_LINKAGE_GLOBAL 1
+#define BTF_LINKAGE_EXTERN 2
+
/* Mapping of CTF variables to the IDs they will be assigned when they are
converted to BTF_KIND_VAR type records. Strictly accounts for the index
from the start of the variable type entries, does not include the number
@@ -314,6 +318,9 @@ btf_collect_datasec (ctf_container_ref ctfc)
continue;
const char *section_name = node->get_section ();
+ /* Mark extern variables. */
+ if (DECL_EXTERNAL (node->decl))
+ dvd->dvd_visibility = BTF_LINKAGE_EXTERN;
if (section_name == NULL)
{
@@ -676,7 +683,7 @@ btf_asm_varent (ctf_dvdef_ref var)
dw2_asm_output_data (4, var->dvd_name_offset, "btv_name");
dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_VAR, 0, 0), "btv_info");
dw2_asm_output_data (4, get_btf_id (var->dvd_type), "btv_type");
- dw2_asm_output_data (4, (var->dvd_visibility ? 1 : 0), "btv_linkage");
+ dw2_asm_output_data (4, var->dvd_visibility, "btv_linkage");
}
/* Asm'out a member description following a BTF_KIND_STRUCT or
new file mode 100644
@@ -0,0 +1,24 @@
+/* Test BTF generation for extern variables. */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -gbtf -dA" } */
+
+/* Expect 4 variables. */
+/* { dg-final { scan-assembler-times "\[\t \]0xe000000\[\t \]+\[^\n\]*btv_info" 4 } } */
+
+/* 2 extern, 1 global, 1 static. */
+/* { dg-final { scan-assembler-times "\[\t \]0\[\t \]+\[^\n\]*btv_linkage" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0x1\[\t \]+\[^\n\]*btv_linkage" 1 } } */
+/* { dg-final { scan-assembler-times "\[\t \]0x2\[\t \]+\[^\n\]*btv_linkage" 2 } } */
+
+extern int a;
+extern const int b;
+int c;
+static const int d = 5;
+
+int foo (int x)
+{
+ c = a + b + x;
+
+ return c + d;
+}
@@ -182,7 +182,7 @@ struct btf_param
information about the variable. */
struct btf_var
{
- uint32_t linkage; /* Currently only 0=static or 1=global. */
+ uint32_t linkage; /* 0=static, 1=global, 2=extern. */
};
/* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,