On 12/7/22 12:57, David Faust wrote:
The eBPF loader expects to find entries for functions declared as extern
in the corresponding BTF_KIND_DATASEC record, but we were not generating
these entries.
This patch adds support for the 'extern' linkage of function types in
BTF, and creates entries for for them BTF_KIND_DATASEC records as needed.
PR target/106773
gcc/
* btfout.cc (get_section_name): New function.
(btf_collect_datasec): Use it here. Process functions, marking them
'extern' and generating DATASEC entries for them as appropriate. Move
creation of BTF_KIND_FUNC records to here...
(btf_dtd_emit_preprocess_cb): ... from here.
gcc/testsuite/
* gcc.dg/debug/btf/btf-datasec-2.c: New test.
* gcc.dg/debug/btf/btf-function-6.c: New test.
include/
* btf.h (struct btf_var_secinfo): Update comments with notes about
extern functions.
---
gcc/btfout.cc | 129 ++++++++++++------
.../gcc.dg/debug/btf/btf-datasec-2.c | 28 ++++
.../gcc.dg/debug/btf/btf-function-6.c | 19 +++
include/btf.h | 9 +-
4 files changed, 139 insertions(+), 46 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-function-6.c
diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 05f3a3f9b6e..d7ead377ec5 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -294,7 +294,35 @@ btf_datasec_push_entry (ctf_container_ref ctfc, const char
*secname,
ds.entries.safe_push (info);
datasecs.safe_push (ds);
- num_types_created++;
+}
+
+
+/* Return the section name, as of interest to btf_collect_datasec, for the
+ given symtab node. Note that this deliberately returns NULL for objects
+ which do not go in a section btf_collect_datasec cares about. */
"Dot, space, space, new sentence."
+static const char *
+get_section_name (symtab_node *node)
+{
+ const char *section_name = node->get_section ();
+
+ if (section_name == NULL)
+ {
+ switch (categorize_decl_for_section (node->decl, 0))
+ {
+ case SECCAT_BSS:
+ section_name = ".bss";
+ break;
+ case SECCAT_DATA:
+ section_name = ".data";
+ break;
+ case SECCAT_RODATA:
+ section_name = ".rodata";
+ break;
+ default:;
+ }
+ }
+
+ return section_name;
}
/* Construct all BTF_KIND_DATASEC records for CTFC. One such record is created
@@ -305,7 +333,60 @@ btf_datasec_push_entry (ctf_container_ref ctfc, const char
*secname,
static void
btf_collect_datasec (ctf_container_ref ctfc)
{
- /* See cgraph.h struct symtab_node, which varpool_node extends. */
+ cgraph_node *func;
+ FOR_EACH_FUNCTION (func)
+ {
+ dw_die_ref die = lookup_decl_die (func->decl);
+ if (die == NULL)
+ continue;
+
+ ctf_dtdef_ref dtd = ctf_dtd_lookup (ctfc, die);
+ if (dtd == NULL)
+ continue;
+
+ /* Functions actually get two types: a BTF_KIND_FUNC_PROTO, and
+ also a BTF_KIND_FUNC. But the CTF container only allocates one
+ type per function, which matches closely with BTF_KIND_FUNC_PROTO.
+ For each such function, also allocate a BTF_KIND_FUNC entry.
+ These will be output later. */
"Dot, space, space, new sentence."
+ ctf_dtdef_ref func_dtd = ggc_cleared_alloc<ctf_dtdef_t> ();
+ func_dtd->dtd_data = dtd->dtd_data;
+ func_dtd->dtd_data.ctti_type = dtd->dtd_type;
+ func_dtd->linkage = dtd->linkage;
+ func_dtd->dtd_type = num_types_added + num_types_created;
+
+ /* Only the BTF_KIND_FUNC type actually references the name. The
+ BTF_KIND_FUNC_PROTO is always anonymous. */
+ dtd->dtd_data.ctti_name = 0;
+
+ vec_safe_push (funcs, func_dtd);
+ num_types_created++;
+
+ /* Mark any 'extern' funcs and add DATASEC entries for them. */
+ if (DECL_EXTERNAL (func->decl))
+ {
+ func_dtd->linkage = BTF_LINKAGE_EXTERN;
+
What is the expected BTF when both decl and definition are present:
extern int extfunc(int x);
int extfunc (int x) {
int y = foo ();
return y;
}
+ const char *section_name = get_section_name (func);
+ /* Note: get_section_name () returns NULL for functions in text
+ section. This is intentional, since we do not want to generate
+ DATASEC entries for them. */
"Dot, space, space, new sentence."
+ if (section_name == NULL)
+ continue;
+
+ struct btf_var_secinfo info;
+
+ /* +1 for the sentinel type not in the types map. */
+ info.type = func_dtd->dtd_type + 1;
+
+ /* Both zero at compile time. */
+ info.size = 0;
+ info.offset = 0;
+
+ btf_datasec_push_entry (ctfc, section_name, info);
+ }
+ }
+
varpool_node *node;
FOR_EACH_VARIABLE (node)
{
@@ -317,28 +398,13 @@ btf_collect_datasec (ctf_container_ref ctfc)
if (dvd == NULL)
continue;
- const char *section_name = node->get_section ();
/* Mark extern variables. */
if (DECL_EXTERNAL (node->decl))
dvd->dvd_visibility = BTF_LINKAGE_EXTERN;
+ const char *section_name = get_section_name (node);
if (section_name == NULL)
- {
- switch (categorize_decl_for_section (node->decl, 0))
- {
- case SECCAT_BSS:
- section_name = ".bss";
- break;
- case SECCAT_DATA:
- section_name = ".data";
- break;
- case SECCAT_RODATA:
- section_name = ".rodata";
- break;
- default:
- continue;
- }
- }
+ continue;
struct btf_var_secinfo info;
@@ -363,6 +429,8 @@ btf_collect_datasec (ctf_container_ref ctfc)
btf_datasec_push_entry (ctfc, section_name, info);
}
+
+ num_types_created += datasecs.length ();
}
/* Return true if the type ID is that of a type which will not be emitted (for
@@ -461,29 +529,6 @@ btf_dtd_emit_preprocess_cb (ctf_container_ref ctfc,
ctf_dtdef_ref dtd)
if (!btf_emit_id_p (dtd->dtd_type))
return;
- uint32_t btf_kind
- = get_btf_kind (CTF_V2_INFO_KIND (dtd->dtd_data.ctti_info));
-
- if (btf_kind == BTF_KIND_FUNC_PROTO)
- {
- /* Functions actually get two types: a BTF_KIND_FUNC_PROTO, and
- also a BTF_KIND_FUNC. But the CTF container only allocates one
- type per function, which matches closely with BTF_KIND_FUNC_PROTO.
- For each such function, also allocate a BTF_KIND_FUNC entry.
- These will be output later. */
- ctf_dtdef_ref func_dtd = ggc_cleared_alloc<ctf_dtdef_t> ();
- func_dtd->dtd_data = dtd->dtd_data;
- func_dtd->dtd_data.ctti_type = dtd->dtd_type;
- func_dtd->linkage = dtd->linkage;
-
- vec_safe_push (funcs, func_dtd);
- num_types_created++;
-
- /* Only the BTF_KIND_FUNC type actually references the name. The
- BTF_KIND_FUNC_PROTO is always anonymous. */
- dtd->dtd_data.ctti_name = 0;
- }
-
ctfc->ctfc_num_vlen_bytes += btf_calc_num_vbytes (dtd);
}
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
new file mode 100644
index 00000000000..f4b298cf019
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
@@ -0,0 +1,28 @@
+/* Test BTF generation of DATASEC records for extern functions.
+
+ Only functions declared extern should have entries in DATASEC records. */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -gbtf -dA" } */
+
+/* Expect one DATASEC with vlen=1 (.foo_sec) and one with vlen=2 (.bar_sec) */
+/* { dg-final { scan-assembler-times "0xf000002\[\t \]+\[^\n\]*btt_info" 1 } }
*/
+/* { dg-final { scan-assembler-times "0xf000001\[\t \]+\[^\n\]*btt_info" 1 } }
*/
+
+/* Function entries should have offset and size of 0 at compile time. */
+/* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_offset" 3 } } */
+/* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_size" 3 } } */
+
+extern int foo (int a) __attribute__((section(".foo_sec")));
+
+
+extern int bar (int b) __attribute__((section(".bar_sec")));
+extern void chacha (void) __attribute__((section(".bar_sec")));
+
+__attribute__((section(".foo_sec")))
+void baz (int *x)
+{
+ chacha ();
+
+ *x = foo (bar (*x));
+}
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-function-6.c
b/gcc/testsuite/gcc.dg/debug/btf/btf-function-6.c
new file mode 100644
index 00000000000..48a946ab14b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-function-6.c
@@ -0,0 +1,19 @@
+/* Test BTF extern linkage for functions.
+
+ We expect to see one BTF_KIND_FUNC type with global linkage (foo), and
+ one BTF_KIND_FUNC type with extern linkage (extfunc). */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -gbtf -dA" } */
+
+/* { dg-final { scan-assembler-times "btt_info: kind=12, kflag=0, linkage=2" 1
} } */
+/* { dg-final { scan-assembler-times "btt_info: kind=12, kflag=0, linkage=1" 1
} } */
+
+extern int extfunc(int a, int b);
+
+int foo (int x) {
+
+ int y = extfunc (x, x+1);
+
+ return y;
+}
diff --git a/include/btf.h b/include/btf.h
index 9a757ce5bc9..f41ea94b75f 100644
--- a/include/btf.h
+++ b/include/btf.h
@@ -186,12 +186,13 @@ struct btf_var
};
/* BTF_KIND_DATASEC is followed by VLEN struct btf_var_secinfo entries,
- which describe all BTF_KIND_VAR types contained in the section. */
+ which describe all BTF_KIND_VAR or extern BTF_KIND_FUNC types contained
+ in the section. */
struct btf_var_secinfo
{
- uint32_t type; /* Type of variable. */
- uint32_t offset; /* In-section offset of variable (in bytes). */
- uint32_t size; /* Size (in bytes) of variable. */
+ uint32_t type; /* Type of BTF_KIND_VAR or BTF_KIND_FUNC item. */
+ uint32_t offset; /* In-section offset (in bytes) of item. */
+ uint32_t size; /* Size (in bytes) of item. */
};
/* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
