bpf/scripts: Generate GCC compatible helpers

Commit Message

James Hilliard July 6, 2022, 2:06 p.m. UTC

The current bpf_helper_defs.h helpers are llvm specific and don't work
correctly with gcc.

Generate gcc compatible headers based on the format in bpf-helpers.h.

See:
https://github.com/gcc-mirror/gcc/blob/releases/gcc-12.1.0/gcc/config/bpf/bpf-helpers.h#L24-L27

Signed-off-by: James Hilliard <[e-mail]>
---
 scripts/bpf_doc.py | 43 ++++++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 17 deletions(-)

Comments

Daniel Borkmann July 6, 2022, 5:12 p.m. UTC | #1

On 7/6/22 4:06 PM, James Hilliard wrote:
> The current bpf_helper_defs.h helpers are llvm specific and don't work
> correctly with gcc.
> 
> Generate gcc compatible headers based on the format in bpf-helpers.h.
> 
> See:
> https://github.com/gcc-mirror/gcc/blob/releases/gcc-12.1.0/gcc/config/bpf/bpf-helpers.h#L24-L27
> 
> Signed-off-by: James Hilliard <[e-mail]>

Please improve the commit description a bit with all the necessary context
around this, and perhaps also provide a small before/after extract around
the bpf-helpers.h. The github.com/gcc-mirror could stay as reference but all
details should be self-explanatory in commit description.

Thanks,
Daniel

Patch

diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index a0ec321469bd..36fb400a5731 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -739,6 +739,24 @@  class PrinterHelpers(Printer):
 
     seen_helpers = set()
 
+    def print_args(self, proto):
+        comma = ''
+        for i, a in enumerate(proto['args']):
+            t = a['type']
+            n = a['name']
+            if proto['name'] in self.overloaded_helpers and i == 0:
+                    t = 'void'
+                    n = 'ctx'
+            one_arg = '{}{}'.format(comma, self.map_type(t))
+            if n:
+                if a['star']:
+                    one_arg += ' {}'.format(a['star'])
+                else:
+                    one_arg += ' '
+                one_arg += '{}'.format(n)
+            comma = ', '
+            print(one_arg, end='')
+
     def print_one(self, helper):
         proto = helper.proto_break_down()
 
@@ -762,26 +780,17 @@  class PrinterHelpers(Printer):
                 print(' *{}{}'.format(' \t' if line else '', line))
 
         print(' */')
+        print('#if __GNUC__ && !__clang__')
+        print('%s %s%s(' % (self.map_type(proto['ret_type']),
+                                      proto['ret_star'], proto['name']), end='')
+        self.print_args(proto)
+        print(') __attribute__((kernel_helper(%d)));' % len(self.seen_helpers))
+        print('#else')
         print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
                                       proto['ret_star'], proto['name']), end='')
-        comma = ''
-        for i, a in enumerate(proto['args']):
-            t = a['type']
-            n = a['name']
-            if proto['name'] in self.overloaded_helpers and i == 0:
-                    t = 'void'
-                    n = 'ctx'
-            one_arg = '{}{}'.format(comma, self.map_type(t))
-            if n:
-                if a['star']:
-                    one_arg += ' {}'.format(a['star'])
-                else:
-                    one_arg += ' '
-                one_arg += '{}'.format(n)
-            comma = ', '
-            print(one_arg, end='')
-
+        self.print_args(proto)
         print(') = (void *) %d;' % len(self.seen_helpers))
+        print('#endif')
         print('')
 
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