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Date: Fri, 28 Oct 2022 11:06:58 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Qing Zhang <zhangqing@...ngson.cn>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/10] LoongArch: modules/ftrace: Initialize PLT at
load time
Hi, Qing,
Maybe this patch can be squashed to another one? If not, please move
it earlier because it looks like some preparation work.
Huacai
On Mon, Sep 19, 2022 at 11:16 AM Qing Zhang <zhangqing@...ngson.cn> wrote:
>
> To Implement ftrace trampiones through plt entry.
>
> Tested by forcing ftrace_make_call() to use the module PLT, and then
> loading up a module after setting up ftrace with:
>
> | echo ":mod:<module-name>" > set_ftrace_filter;
> | echo function > current_tracer;
> | modprobe <module-name>
>
> Since FTRACE_ADDR/FTRACE_REGS_ADDR is only defined when CONFIG_DYNAMIC_FTRACE
> is selected, we wrap its use along with most of module_init_ftrace_plt() with
> ifdeffery rather than using IS_ENABLED().
>
> Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
> ---
> arch/loongarch/include/asm/ftrace.h | 4 ++
> arch/loongarch/include/asm/inst.h | 3 +
> arch/loongarch/include/asm/module.h | 5 +-
> arch/loongarch/include/asm/module.lds.h | 1 +
> arch/loongarch/kernel/ftrace_dyn.c | 79 +++++++++++++++++++++++++
> arch/loongarch/kernel/inst.c | 11 ++++
> arch/loongarch/kernel/module-sections.c | 11 ++++
> arch/loongarch/kernel/module.c | 47 +++++++++++++++
> 8 files changed, 160 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> index 5cc13ae48164..807226aad1c0 100644
> --- a/arch/loongarch/include/asm/ftrace.h
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -6,6 +6,10 @@
> #ifndef _ASM_LOONGARCH_FTRACE_H
> #define _ASM_LOONGARCH_FTRACE_H
>
> +#define FTRACE_PLT_IDX 0
> +#define FTRACE_REGS_PLT_IDX 1
> +#define NR_FTRACE_PLTS 2
> +
> #ifdef CONFIG_FUNCTION_TRACER
> #define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
>
> diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
> index f4a12f872a71..5a1aa977ae20 100644
> --- a/arch/loongarch/include/asm/inst.h
> +++ b/arch/loongarch/include/asm/inst.h
> @@ -15,10 +15,12 @@
>
> #define ADDR_IMMMASK_LU52ID 0xFFF0000000000000
> #define ADDR_IMMMASK_LU32ID 0x000FFFFF00000000
> +#define ADDR_IMMMASK_LU12IW 0x00000000FFFFF000
> #define ADDR_IMMMASK_ADDU16ID 0x00000000FFFF0000
>
> #define ADDR_IMMSHIFT_LU52ID 52
> #define ADDR_IMMSHIFT_LU32ID 32
> +#define ADDR_IMMSHIFT_LU12IW 12
> #define ADDR_IMMSHIFT_ADDU16ID 16
>
> #define ADDR_IMM(addr, INSN) ((addr & ADDR_IMMMASK_##INSN) >> ADDR_IMMSHIFT_##INSN)
> @@ -346,6 +348,7 @@ u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj,
> enum loongarch_gpr rk);
> u32 larch_insn_gen_move(enum loongarch_gpr rd, enum loongarch_gpr rj);
>
> +u32 larch_insn_gen_lu12iw(enum loongarch_gpr rd, int imm);
> u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm);
> u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
> u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest);
> diff --git a/arch/loongarch/include/asm/module.h b/arch/loongarch/include/asm/module.h
> index b29b19a46f42..a311cfec2b23 100644
> --- a/arch/loongarch/include/asm/module.h
> +++ b/arch/loongarch/include/asm/module.h
> @@ -20,6 +20,9 @@ struct mod_arch_specific {
> struct mod_section got;
> struct mod_section plt;
> struct mod_section plt_idx;
> +
> + /* for CONFIG_DYNAMIC_FTRACE */
> + struct plt_entry *ftrace_trampolines;
> };
>
> struct got_entry {
> @@ -49,7 +52,7 @@ static inline struct plt_entry emit_plt_entry(unsigned long val)
> {
> u32 lu12iw, lu32id, lu52id, jirl;
>
> - lu12iw = (lu12iw_op << 25 | (((val >> 12) & 0xfffff) << 5) | LOONGARCH_GPR_T1);
> + lu12iw = larch_insn_gen_lu12iw(LOONGARCH_GPR_T1, ADDR_IMM(val, LU12IW));
> lu32id = larch_insn_gen_lu32id(LOONGARCH_GPR_T1, ADDR_IMM(val, LU32ID));
> lu52id = larch_insn_gen_lu52id(LOONGARCH_GPR_T1, LOONGARCH_GPR_T1, ADDR_IMM(val, LU52ID));
> jirl = larch_insn_gen_jirl(0, LOONGARCH_GPR_T1, 0, (val & 0xfff));
> diff --git a/arch/loongarch/include/asm/module.lds.h b/arch/loongarch/include/asm/module.lds.h
> index a3d1bc0fcc72..438f09d4ccf4 100644
> --- a/arch/loongarch/include/asm/module.lds.h
> +++ b/arch/loongarch/include/asm/module.lds.h
> @@ -5,4 +5,5 @@ SECTIONS {
> .got : { BYTE(0) }
> .plt : { BYTE(0) }
> .plt.idx : { BYTE(0) }
> + .ftrace_trampoline : { BYTE(0) }
> }
> diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
> index f538829312d7..dd37185d446e 100644
> --- a/arch/loongarch/kernel/ftrace_dyn.c
> +++ b/arch/loongarch/kernel/ftrace_dyn.c
> @@ -9,6 +9,7 @@
> #include <linux/uaccess.h>
>
> #include <asm/inst.h>
> +#include <asm/module.h>
>
> static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
> bool validate)
> @@ -72,12 +73,63 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
> return ftrace_modify_code(pc, old, new, true);
> }
>
> +static inline int __get_mod(struct module **mod, unsigned long addr)
> +{
> + preempt_disable();
> + *mod = __module_text_address(addr);
> + preempt_enable();
> +
> + if (WARN_ON(!(*mod)))
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
> +{
> + struct plt_entry *plt = mod->arch.ftrace_trampolines;
> +
> + if (addr == FTRACE_ADDR)
> + return &plt[FTRACE_PLT_IDX];
> + if (addr == FTRACE_REGS_ADDR &&
> + IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
> + return &plt[FTRACE_REGS_PLT_IDX];
> +
> + return NULL;
> +}
> +
> +static unsigned long get_plt_addr(struct module *mod, unsigned long addr)
> +{
> + struct plt_entry *plt;
> +
> + plt = get_ftrace_plt(mod, addr);
> + if (!plt) {
> + pr_err("ftrace: no module PLT for %ps\n", (void *)addr);
> + return -EINVAL;
> + }
> +
> + return (unsigned long)plt;
> +}
> +
> int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> {
> unsigned long pc;
> + long offset;
> u32 old, new;
>
> pc = rec->ip + LOONGARCH_INSN_SIZE;
> + offset = (long)pc - (long)addr;
> +
> + if (offset < -SZ_128M || offset >= SZ_128M) {
> + int ret;
> + struct module *mod;
> +
> + ret = __get_mod(&mod, pc);
> + if (ret)
> + return ret;
> +
> + addr = get_plt_addr(mod, addr);
> + }
>
> old = larch_insn_gen_nop();
> new = larch_insn_gen_bl(pc, addr);
> @@ -89,9 +141,22 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
> unsigned long addr)
> {
> unsigned long pc;
> + long offset;
> u32 old, new;
>
> pc = rec->ip + LOONGARCH_INSN_SIZE;
> + offset = (long)pc - (long)addr;
> +
> + if (offset < -SZ_128M || offset >= SZ_128M) {
> + int ret;
> + struct module *mod;
> +
> + ret = __get_mod(&mod, pc);
> + if (ret)
> + return ret;
> +
> + addr = get_plt_addr(mod, addr);
> + }
>
> new = larch_insn_gen_nop();
> old = larch_insn_gen_bl(pc, addr);
> @@ -108,6 +173,20 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> u32 old, new;
>
> pc = rec->ip + LOONGARCH_INSN_SIZE;
> + offset = (long)pc - (long)addr;
> +
> + if (offset < -SZ_128M || offset >= SZ_128M) {
> + int ret;
> + struct module *mod;
> +
> + ret = __get_mod(&mod, pc);
> + if (ret)
> + return ret;
> +
> + addr = get_plt_addr(mod, addr);
> +
> + old_addr = get_plt_addr(mod, old_addr);
> + }
>
> old = larch_insn_gen_bl(pc, old_addr);
> new = larch_insn_gen_bl(pc, addr);
> diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
> index 2d2e942eb06a..0d6bd7000ba6 100644
> --- a/arch/loongarch/kernel/inst.c
> +++ b/arch/loongarch/kernel/inst.c
> @@ -103,6 +103,17 @@ u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest)
> return insn.word;
> }
>
> +u32 larch_insn_gen_lu12iw(enum loongarch_gpr rd, int imm)
> +{
> + union loongarch_instruction insn;
> +
> + insn.reg1i20_format.opcode = lu12iw_op;
> + insn.reg1i20_format.rd = rd;
> + insn.reg1i20_format.immediate = imm;
> +
> + return insn.word;
> +}
> +
> u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm)
> {
> union loongarch_instruction insn;
> diff --git a/arch/loongarch/kernel/module-sections.c b/arch/loongarch/kernel/module-sections.c
> index d296a70b758f..bd1a96691c98 100644
> --- a/arch/loongarch/kernel/module-sections.c
> +++ b/arch/loongarch/kernel/module-sections.c
> @@ -4,6 +4,7 @@
> */
>
> #include <linux/elf.h>
> +#include <linux/ftrace.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
>
> @@ -103,6 +104,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
> char *secstrings, struct module *mod)
> {
> unsigned int i, num_plts = 0, num_gots = 0;
> + Elf_Shdr *tramp = NULL;
>
> /*
> * Find the empty .plt sections.
> @@ -114,6 +116,8 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
> mod->arch.plt.shdr = sechdrs + i;
> else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx"))
> mod->arch.plt_idx.shdr = sechdrs + i;
> + else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline"))
> + tramp = sechdrs + i;
> }
>
> if (!mod->arch.got.shdr) {
> @@ -166,5 +170,12 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
> mod->arch.plt_idx.num_entries = 0;
> mod->arch.plt_idx.max_entries = num_plts;
>
> + if (tramp) {
> + tramp->sh_type = SHT_NOBITS;
> + tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
> + tramp->sh_addralign = __alignof__(struct plt_entry);
> + tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry);
> + }
> +
> return 0;
> }
> diff --git a/arch/loongarch/kernel/module.c b/arch/loongarch/kernel/module.c
> index 097595b2fc14..e036b1ebf98e 100644
> --- a/arch/loongarch/kernel/module.c
> +++ b/arch/loongarch/kernel/module.c
> @@ -10,6 +10,7 @@
>
> #include <linux/moduleloader.h>
> #include <linux/elf.h>
> +#include <linux/ftrace.h>
> #include <linux/mm.h>
> #include <linux/numa.h>
> #include <linux/vmalloc.h>
> @@ -17,6 +18,7 @@
> #include <linux/fs.h>
> #include <linux/string.h>
> #include <linux/kernel.h>
> +#include <asm/inst.h>
>
> static int rela_stack_push(s64 stack_value, s64 *rela_stack, size_t *rela_stack_top)
> {
> @@ -456,3 +458,48 @@ void *module_alloc(unsigned long size)
> return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
> GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE, __builtin_return_address(0));
> }
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +static const Elf_Shdr *find_section(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
> + const char *name)
> +{
> + const Elf_Shdr *s, *se;
> + const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
> +
> + for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
> + if (strcmp(name, secstrs + s->sh_name) == 0)
> + return s;
> + }
> +
> + return NULL;
> +}
> +#endif
> +
> +static int module_init_ftrace_plt(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
> + struct module *mod)
> +{
> +#ifdef CONFIG_DYNAMIC_FTRACE
> + const Elf_Shdr *s;
> + struct plt_entry *ftrace_plts;
> +
> + s = find_section(hdr, sechdrs, ".ftrace_trampoline");
> + if (!s)
> + return -ENOEXEC;
> +
> + ftrace_plts = (void *)s->sh_addr;
> +
> + ftrace_plts[FTRACE_PLT_IDX] = emit_plt_entry(FTRACE_ADDR);
> +
> + if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
> + ftrace_plts[FTRACE_REGS_PLT_IDX] = emit_plt_entry(FTRACE_REGS_ADDR);
> +
> + mod->arch.ftrace_trampolines = ftrace_plts;
> +#endif
> + return 0;
> +}
> +
> +int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *mod)
> +{
> + return module_init_ftrace_plt(hdr, sechdrs, mod);
> +
> +}
> --
> 2.36.1
>
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