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fa624569b7
The compiler may choose not to emit type information in DWARF for
external symbols. Clang, for example, does this for symbols not
defined in the current TU.
To provide a way to work around this issue, add support for
__gendwarfksyms_ptr_<symbol> pointers that force the compiler to emit
the necessary type information in DWARF also for the missing symbols.
Example usage:
#define GENDWARFKSYMS_PTR(sym) \
static typeof(sym) *__gendwarfksyms_ptr_##sym __used \
__section(".discard.gendwarfksyms") = &sym;
extern int external_symbol(void);
GENDWARFKSYMS_PTR(external_symbol);
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
33 lines
840 B
C
33 lines
840 B
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2024 Google LLC
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*
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* Example for symbol pointers. When compiled with Clang, gendwarfkyms
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* uses a symbol pointer for `f`.
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*
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* $ clang -g -c examples/symbolptr.c -o examples/symbolptr.o
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* $ echo -e "f\ng\np" | ./gendwarfksyms -d examples/symbolptr.o
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*/
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/* Kernel macros for userspace testing. */
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#ifndef __used
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#define __used __attribute__((__used__))
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#endif
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#ifndef __section
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#define __section(section) __attribute__((__section__(section)))
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#endif
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#define __GENDWARFKSYMS_EXPORT(sym) \
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static typeof(sym) *__gendwarfksyms_ptr_##sym __used \
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__section(".discard.gendwarfksyms") = &sym;
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extern void f(unsigned int arg);
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void g(int *arg);
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void g(int *arg) {}
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struct s;
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extern struct s *p;
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__GENDWARFKSYMS_EXPORT(f);
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__GENDWARFKSYMS_EXPORT(g);
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__GENDWARFKSYMS_EXPORT(p);
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