Re: [RFC PATCH 3/4] objtool/powerpc: Enable objtool to be built on ppc

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
> This patch adds [stub] implementations for required
> functions, inorder to enable objtool build on powerpc.

Should we put some exit() or abort() in the stubs that are not supposed 
to be used at all ?

> 
> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
> ---
>   arch/powerpc/Kconfig                          |  1 +
>   tools/objtool/arch/powerpc/Build              |  2 +
>   tools/objtool/arch/powerpc/decode.c           | 73 +++++++++++++++++++
>   .../arch/powerpc/include/arch/cfi_regs.h      | 11 +++
>   tools/objtool/arch/powerpc/include/arch/elf.h |  8 ++
>   .../arch/powerpc/include/arch/endianness.h    |  9 +++
>   .../arch/powerpc/include/arch/special.h       | 21 ++++++
>   tools/objtool/arch/powerpc/special.c          | 19 +++++
>   8 files changed, 144 insertions(+)
>   create mode 100644 tools/objtool/arch/powerpc/Build
>   create mode 100644 tools/objtool/arch/powerpc/decode.c
>   create mode 100644 tools/objtool/arch/powerpc/include/arch/cfi_regs.h
>   create mode 100644 tools/objtool/arch/powerpc/include/arch/elf.h
>   create mode 100644 tools/objtool/arch/powerpc/include/arch/endianness.h
>   create mode 100644 tools/objtool/arch/powerpc/include/arch/special.h
>   create mode 100644 tools/objtool/arch/powerpc/special.c
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 174edabb74fa..732a3f91ee5e 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -232,6 +232,7 @@ config PPC
>   	select HAVE_MOD_ARCH_SPECIFIC
>   	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>   	select HAVE_OPTPROBES
> +	select HAVE_OBJTOOL			if PPC64
>   	select HAVE_PERF_EVENTS
>   	select HAVE_PERF_EVENTS_NMI		if PPC64
>   	select HAVE_PERF_REGS
> diff --git a/tools/objtool/arch/powerpc/Build b/tools/objtool/arch/powerpc/Build
> new file mode 100644
> index 000000000000..d24d5636a5b8
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/Build
> @@ -0,0 +1,2 @@
> +objtool-y += decode.o
> +objtool-y += special.o
> diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
> new file mode 100644
> index 000000000000..e3b77a6ce357
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/decode.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <objtool/check.h>
> +#include <objtool/elf.h>
> +#include <objtool/arch.h>
> +#include <objtool/warn.h>
> +#include <objtool/builtin.h>
> +
> +unsigned long arch_dest_reloc_offset(int addend)
> +{
> +	return addend;
> +}
> +
> +bool arch_callee_saved_reg(unsigned char reg)
> +{
> +	return false;
> +}
> +
> +int arch_decode_hint_reg(u8 sp_reg, int *base)
> +{
> +	return 0;
> +}
> +
> +const char *arch_nop_insn(int len)
> +{
> +	return NULL;
> +}
> +
> +const char *arch_ret_insn(int len)
> +{
> +	return NULL;
> +}
> +
> +int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
> +			    unsigned long offset, unsigned int maxlen,
> +			    unsigned int *len, enum insn_type *type,
> +			    unsigned long *immediate,
> +			    struct list_head *ops_list)
> +{
> +	u32 insn;
> +
> +	*immediate = 0;
> +	memcpy(&insn, sec->data->d_buf+offset, 4);
> +	*len = 4;
> +	*type = INSN_OTHER;
> +
> +	return 0;
> +}
> +
> +unsigned long arch_jump_destination(struct instruction *insn)
> +{
> +	return insn->offset +  insn->immediate;
> +}
> +
> +void arch_initial_func_cfi_state(struct cfi_init_state *state)
> +{
> +	int i;
> +
> +	for (i = 0; i < CFI_NUM_REGS; i++) {
> +		state->regs[i].base = CFI_UNDEFINED;
> +		state->regs[i].offset = 0;
> +	}
> +
> +	/* initial CFA (call frame address) */
> +	state->cfa.base = CFI_SP;
> +	state->cfa.offset = 0;
> +
> +	/* initial LR (return address) */
> +	state->regs[CFI_RA].base = CFI_CFA;
> +	state->regs[CFI_RA].offset = 0;
> +}
> diff --git a/tools/objtool/arch/powerpc/include/arch/cfi_regs.h b/tools/objtool/arch/powerpc/include/arch/cfi_regs.h
> new file mode 100644
> index 000000000000..59638ebeafc8
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/include/arch/cfi_regs.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#ifndef _OBJTOOL_CFI_REGS_H
> +#define _OBJTOOL_CFI_REGS_H
> +
> +#define CFI_BP 1
> +#define CFI_SP CFI_BP
> +#define CFI_RA 32
> +#define CFI_NUM_REGS 33
> +
> +#endif
> diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
> new file mode 100644
> index 000000000000..3c8ebb7d2a6b
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/include/arch/elf.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#ifndef _OBJTOOL_ARCH_ELF
> +#define _OBJTOOL_ARCH_ELF
> +
> +#define R_NONE R_PPC_NONE
> +
> +#endif /* _OBJTOOL_ARCH_ELF */
> diff --git a/tools/objtool/arch/powerpc/include/arch/endianness.h b/tools/objtool/arch/powerpc/include/arch/endianness.h
> new file mode 100644
> index 000000000000..7c362527da20
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/include/arch/endianness.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _ARCH_ENDIANNESS_H
> +#define _ARCH_ENDIANNESS_H
> +
> +#include <endian.h>
> +
> +#define __TARGET_BYTE_ORDER __LITTLE_ENDIAN
> +
> +#endif /* _ARCH_ENDIANNESS_H */
> diff --git a/tools/objtool/arch/powerpc/include/arch/special.h b/tools/objtool/arch/powerpc/include/arch/special.h
> new file mode 100644
> index 000000000000..ffef9ada7133
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/include/arch/special.h
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _PPC_ARCH_SPECIAL_H
> +#define _PPC_ARCH_SPECIAL_H
> +
> +#define EX_ENTRY_SIZE 8
> +#define EX_ORIG_OFFSET 0
> +#define EX_NEW_OFFSET 4
> +
> +#define JUMP_ENTRY_SIZE 16
> +#define JUMP_ORIG_OFFSET 0
> +#define JUMP_NEW_OFFSET 4
> +#define JUMP_KEY_OFFSET 8
> +
> +#define ALT_ENTRY_SIZE 12
> +#define ALT_ORIG_OFFSET 0
> +#define ALT_NEW_OFFSET 4
> +#define ALT_FEATURE_OFFSET 8
> +#define ALT_ORIG_LEN_OFFSET 10
> +#define ALT_NEW_LEN_OFFSET 11
> +
> +#endif /* _PPC_ARCH_SPECIAL_H */
> diff --git a/tools/objtool/arch/powerpc/special.c b/tools/objtool/arch/powerpc/special.c
> new file mode 100644
> index 000000000000..e3e75cbab858
> --- /dev/null
> +++ b/tools/objtool/arch/powerpc/special.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <string.h>
> +
> +#include <objtool/special.h>
> +#include <objtool/builtin.h>
> +
> +
> +bool arch_support_alt_relocation(struct special_alt *special_alt,
> +				 struct instruction *insn,
> +				 struct reloc *reloc)
> +{
> +	return false;
> +}
> +
> +struct reloc *arch_find_switch_table(struct objtool_file *file,
> +				    struct instruction *insn)
> +{
> +	return NULL;
> +}