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Date: Sat, 21 Oct 2023 16:08:35 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v3 4/8] objtool/LoongArch: Enable orc to be built
Hi, Tiezhu,
On Fri, Oct 20, 2023 at 10:27 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> Implement arch-specific init_orc_entry(), write_orc_entry(), reg_name(),
> orc_type_name(), print_reg() and orc_print_dump(), then set BUILD_ORC as
> y to build the orc related files.
>
> Co-developed-by: Jinyang He <hejinyang@...ngson.cn>
> Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
> Co-developed-by: Youling Tang <tangyouling@...ngson.cn>
> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
> tools/arch/loongarch/include/asm/orc_types.h | 58 +++++++++
> tools/objtool/Makefile | 4 +
> tools/objtool/arch/loongarch/Build | 1 +
> tools/objtool/arch/loongarch/decode.c | 16 +++
> tools/objtool/arch/loongarch/orc.c | 171 +++++++++++++++++++++++++++
> 5 files changed, 250 insertions(+)
> create mode 100644 tools/arch/loongarch/include/asm/orc_types.h
> create mode 100644 tools/objtool/arch/loongarch/orc.c
>
> diff --git a/tools/arch/loongarch/include/asm/orc_types.h b/tools/arch/loongarch/include/asm/orc_types.h
> new file mode 100644
> index 0000000..caf1f71
> --- /dev/null
> +++ b/tools/arch/loongarch/include/asm/orc_types.h
> @@ -0,0 +1,58 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _ORC_TYPES_H
> +#define _ORC_TYPES_H
> +
> +#include <linux/types.h>
> +
> +/*
> + * The ORC_REG_* registers are base registers which are used to find other
> + * registers on the stack.
> + *
> + * ORC_REG_PREV_SP, also known as DWARF Call Frame Address (CFA), is the
> + * address of the previous frame: the caller's SP before it called the current
> + * function.
> + *
> + * ORC_REG_UNDEFINED means the corresponding register's value didn't change in
> + * the current frame.
> + *
> + * The most commonly used base registers are SP and FP -- which the previous SP
> + * is usually based on -- and PREV_SP and UNDEFINED -- which the previous FP is
> + * usually based on.
> + *
> + * The rest of the base registers are needed for special cases like entry code
> + * and GCC realigned stacks.
> + */
> +#define ORC_REG_UNDEFINED 0
> +#define ORC_REG_PREV_SP 1
> +#define ORC_REG_SP 2
> +#define ORC_REG_FP 3
> +#define ORC_REG_MAX 4
> +
> +#define ORC_TYPE_UNDEFINED 0
> +#define ORC_TYPE_END_OF_STACK 1
> +#define ORC_TYPE_CALL 2
> +#define ORC_TYPE_REGS 3
> +#define ORC_TYPE_REGS_PARTIAL 4
> +
> +#ifndef __ASSEMBLY__
> +/*
> + * This struct is more or less a vastly simplified version of the DWARF Call
> + * Frame Information standard. It contains only the necessary parts of DWARF
> + * CFI, simplified for ease of access by the in-kernel unwinder. It tells the
> + * unwinder how to find the previous SP and FP (and sometimes entry regs) on
> + * the stack for a given code address. Each instance of the struct corresponds
> + * to one or more code locations.
> + */
> +struct orc_entry {
> + s16 sp_offset;
> + s16 fp_offset;
> + s16 ra_offset;
> + unsigned int sp_reg:4;
> + unsigned int fp_reg:4;
> + unsigned int ra_reg:4;
> + unsigned int type:3;
> + unsigned int signal:1;
> +};
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* _ORC_TYPES_H */
> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> index 83b100c..bf7f7f8 100644
> --- a/tools/objtool/Makefile
> +++ b/tools/objtool/Makefile
> @@ -57,6 +57,10 @@ ifeq ($(SRCARCH),x86)
> BUILD_ORC := y
> endif
>
> +ifeq ($(SRCARCH),loongarch)
> + BUILD_ORC := y
> +endif
> +
> export BUILD_ORC
> export srctree OUTPUT CFLAGS SRCARCH AWK
> include $(srctree)/tools/build/Makefile.include
> diff --git a/tools/objtool/arch/loongarch/Build b/tools/objtool/arch/loongarch/Build
> index d24d563..1d4b784 100644
> --- a/tools/objtool/arch/loongarch/Build
> +++ b/tools/objtool/arch/loongarch/Build
> @@ -1,2 +1,3 @@
> objtool-y += decode.o
> objtool-y += special.o
> +objtool-y += orc.o
> diff --git a/tools/objtool/arch/loongarch/decode.c b/tools/objtool/arch/loongarch/decode.c
> index 0ee3333..555b6d0 100644
> --- a/tools/objtool/arch/loongarch/decode.c
> +++ b/tools/objtool/arch/loongarch/decode.c
> @@ -3,6 +3,8 @@
> #include <objtool/check.h>
> #include <objtool/warn.h>
> #include <asm/inst.h>
> +#include <asm/orc_types.h>
> +#include <linux/objtool_types.h>
>
We should add lines here to avoid cross-compile errors:
+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH 258
+#endif
Huacai
> int arch_ftrace_match(char *name)
> {
> @@ -38,6 +40,20 @@ bool arch_callee_saved_reg(unsigned char reg)
>
> int arch_decode_hint_reg(u8 sp_reg, int *base)
> {
> + switch (sp_reg) {
> + case ORC_REG_UNDEFINED:
> + *base = CFI_UNDEFINED;
> + break;
> + case ORC_REG_SP:
> + *base = CFI_SP;
> + break;
> + case ORC_REG_FP:
> + *base = CFI_FP;
> + break;
> + default:
> + return -1;
> + }
> +
> return 0;
> }
>
> diff --git a/tools/objtool/arch/loongarch/orc.c b/tools/objtool/arch/loongarch/orc.c
> new file mode 100644
> index 0000000..873536d
> --- /dev/null
> +++ b/tools/objtool/arch/loongarch/orc.c
> @@ -0,0 +1,171 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <linux/objtool_types.h>
> +#include <asm/orc_types.h>
> +
> +#include <objtool/check.h>
> +#include <objtool/orc.h>
> +#include <objtool/warn.h>
> +#include <objtool/endianness.h>
> +
> +int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi, struct instruction *insn)
> +{
> + struct cfi_reg *fp = &cfi->regs[CFI_FP];
> + struct cfi_reg *ra = &cfi->regs[CFI_RA];
> +
> + memset(orc, 0, sizeof(*orc));
> +
> + if (!cfi) {
> + /*
> + * This is usually either unreachable nops/traps (which don't
> + * trigger unreachable instruction warnings), or
> + * STACK_FRAME_NON_STANDARD functions.
> + */
> + orc->type = ORC_TYPE_UNDEFINED;
> + return 0;
> + }
> +
> + switch (cfi->type) {
> + case UNWIND_HINT_TYPE_UNDEFINED:
> + orc->type = ORC_TYPE_UNDEFINED;
> + return 0;
> + case UNWIND_HINT_TYPE_END_OF_STACK:
> + orc->type = ORC_TYPE_END_OF_STACK;
> + return 0;
> + case UNWIND_HINT_TYPE_CALL:
> + orc->type = ORC_TYPE_CALL;
> + break;
> + case UNWIND_HINT_TYPE_REGS:
> + orc->type = ORC_TYPE_REGS;
> + break;
> + case UNWIND_HINT_TYPE_REGS_PARTIAL:
> + orc->type = ORC_TYPE_REGS_PARTIAL;
> + break;
> + default:
> + WARN_INSN(insn, "unknown unwind hint type %d", cfi->type);
> + return -1;
> + }
> +
> + orc->signal = cfi->signal;
> +
> + switch (cfi->cfa.base) {
> + case CFI_SP:
> + orc->sp_reg = ORC_REG_SP;
> + break;
> + case CFI_FP:
> + orc->sp_reg = ORC_REG_FP;
> + break;
> + default:
> + WARN_INSN(insn, "unknown CFA base reg %d", cfi->cfa.base);
> + return -1;
> + }
> +
> + switch (fp->base) {
> + case CFI_UNDEFINED:
> + orc->fp_reg = ORC_REG_UNDEFINED;
> + orc->fp_offset = 0;
> + break;
> + case CFI_CFA:
> + orc->fp_reg = ORC_REG_PREV_SP;
> + orc->fp_offset = fp->offset;
> + break;
> + case CFI_FP:
> + orc->fp_reg = ORC_REG_FP;
> + break;
> + default:
> + WARN_INSN(insn, "unknown FP base reg %d", fp->base);
> + return -1;
> + }
> +
> + switch (ra->base) {
> + case CFI_UNDEFINED:
> + orc->ra_reg = ORC_REG_UNDEFINED;
> + orc->ra_offset = 0;
> + break;
> + case CFI_CFA:
> + orc->ra_reg = ORC_REG_PREV_SP;
> + orc->ra_offset = ra->offset;
> + break;
> + case CFI_FP:
> + orc->ra_reg = ORC_REG_FP;
> + break;
> + default:
> + WARN_INSN(insn, "unknown RA base reg %d", ra->base);
> + return -1;
> + }
> +
> + orc->sp_offset = cfi->cfa.offset;
> +
> + return 0;
> +}
> +
> +int write_orc_entry(struct elf *elf, struct section *orc_sec,
> + struct section *ip_sec, unsigned int idx,
> + struct section *insn_sec, unsigned long insn_off,
> + struct orc_entry *o)
> +{
> + struct orc_entry *orc;
> +
> + /* populate ORC data */
> + orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
> + memcpy(orc, o, sizeof(*orc));
> +
> + /* populate reloc for ip */
> + if (!elf_init_reloc_text_sym(elf, ip_sec, idx * sizeof(int), idx,
> + insn_sec, insn_off))
> + return -1;
> +
> + return 0;
> +}
> +
> +static const char *reg_name(unsigned int reg)
> +{
> + switch (reg) {
> + case ORC_REG_SP:
> + return "sp";
> + case ORC_REG_FP:
> + return "fp";
> + case ORC_REG_PREV_SP:
> + return "prevsp";
> + default:
> + return "?";
> + }
> +}
> +
> +static const char *orc_type_name(unsigned int type)
> +{
> + switch (type) {
> + case UNWIND_HINT_TYPE_CALL:
> + return "call";
> + case UNWIND_HINT_TYPE_REGS:
> + return "regs";
> + case UNWIND_HINT_TYPE_REGS_PARTIAL:
> + return "regs (partial)";
> + default:
> + return "?";
> + }
> +}
> +
> +static void print_reg(unsigned int reg, int offset)
> +{
> + if (reg == ORC_REG_UNDEFINED)
> + printf(" (und) ");
> + else
> + printf("%s + %3d", reg_name(reg), offset);
> +
> +}
> +
> +void orc_print_dump(struct elf *dummy_elf, struct orc_entry *orc, int i)
> +{
> + printf("type:%s", orc_type_name(orc[i].type));
> +
> + printf(" sp:");
> + print_reg(orc[i].sp_reg, orc[i].sp_offset);
> +
> + printf(" fp:");
> + print_reg(orc[i].fp_reg, orc[i].fp_offset);
> +
> + printf(" ra:");
> + print_reg(orc[i].ra_reg, orc[i].ra_offset);
> +
> + printf(" signal:%d\n", orc[i].signal);
> +}
> --
> 2.1.0
>
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