Messages in this thread Patch in this message | | | From | Alexander Sverdlin <> | Subject | [PATCH v4 2/2] ARM: ftrace: Add MODULE_PLTS support | Date | Tue, 13 Mar 2018 14:53:14 +0100 |
| |
Teach ftrace_make_call() and ftrace_make_nop() about PLTs. Teach PLT code about FTRACE and all its callbacks. Otherwise the following might happen:
------------[ cut here ]------------ WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 __arm_gen_branch+0x83/0x8c() ... Hardware name: LSI Axxia AXM55XX [<c0314a49>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14) [<c03115e9>] (show_stack) from [<c0519f51>] (dump_stack+0x81/0xa8) [<c0519f51>] (dump_stack) from [<c032185d>] (warn_slowpath_common+0x69/0x90) [<c032185d>] (warn_slowpath_common) from [<c03218f3>] (warn_slowpath_null+0x17/0x1c) [<c03218f3>] (warn_slowpath_null) from [<c03143cf>] (__arm_gen_branch+0x83/0x8c) [<c03143cf>] (__arm_gen_branch) from [<c0314337>] (ftrace_make_nop+0xf/0x24) [<c0314337>] (ftrace_make_nop) from [<c038ebcb>] (ftrace_process_locs+0x27b/0x3e8) [<c038ebcb>] (ftrace_process_locs) from [<c0378d79>] (load_module+0x11e9/0x1a44) [<c0378d79>] (load_module) from [<c037974d>] (SyS_finit_module+0x59/0x84) [<c037974d>] (SyS_finit_module) from [<c030e981>] (ret_fast_syscall+0x1/0x18) ---[ end trace e1b64ced7a89adcc ]--- ------------[ cut here ]------------ WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 ftrace_bug+0x1b1/0x234() ... Hardware name: LSI Axxia AXM55XX [<c0314a49>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14) [<c03115e9>] (show_stack) from [<c0519f51>] (dump_stack+0x81/0xa8) [<c0519f51>] (dump_stack) from [<c032185d>] (warn_slowpath_common+0x69/0x90) [<c032185d>] (warn_slowpath_common) from [<c03218f3>] (warn_slowpath_null+0x17/0x1c) [<c03218f3>] (warn_slowpath_null) from [<c038e87d>] (ftrace_bug+0x1b1/0x234) [<c038e87d>] (ftrace_bug) from [<c038ebd5>] (ftrace_process_locs+0x285/0x3e8) [<c038ebd5>] (ftrace_process_locs) from [<c0378d79>] (load_module+0x11e9/0x1a44) [<c0378d79>] (load_module) from [<c037974d>] (SyS_finit_module+0x59/0x84) [<c037974d>] (SyS_finit_module) from [<c030e981>] (ret_fast_syscall+0x1/0x18) ---[ end trace e1b64ced7a89adcd ]--- ftrace failed to modify [<e9ef7006>] 0xe9ef7006 actual: 02:f0:3b:fa ftrace record flags: 0 (0) expected tramp: c0314265
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com> --- arch/arm/include/asm/ftrace.h | 3 +++ arch/arm/include/asm/module.h | 1 + arch/arm/kernel/ftrace.c | 62 ++++++++++++++++++++++++++++++++++++------- arch/arm/kernel/module-plts.c | 47 +++++++++++++++++++++++++++++--- 4 files changed, 100 insertions(+), 13 deletions(-)
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index 9e842ff..faeb6b1 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -19,6 +19,9 @@ struct dyn_arch_ftrace { #ifdef CONFIG_OLD_MCOUNT bool old_mcount; #endif +#ifdef CONFIG_ARM_MODULE_PLTS + struct module *mod; +#endif }; static inline unsigned long ftrace_call_adjust(unsigned long addr) diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h index 6996405..e3d7a51 100644 --- a/arch/arm/include/asm/module.h +++ b/arch/arm/include/asm/module.h @@ -30,6 +30,7 @@ struct plt_entries { struct mod_plt_sec { struct elf32_shdr *plt; + struct plt_entries *plt_ent; int plt_count; }; diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index 5617932..b55355f 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -98,6 +98,19 @@ int ftrace_arch_code_modify_post_process(void) static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) { + s32 offset = addr - pc; + s32 blim = 0xfe000008; + s32 flim = 0x02000004; + + if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) { + blim = 0xff000004; + flim = 0x01000002; + } + + if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS) && + (offset < blim || offset > flim)) + return 0; + return arm_gen_branch_link(pc, addr); } @@ -166,10 +179,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned long new, old; unsigned long ip = rec->ip; + unsigned long aaddr = adjust_address(rec, addr); old = ftrace_nop_replace(rec); - new = ftrace_call_replace(ip, adjust_address(rec, addr)); + new = ftrace_call_replace(ip, aaddr); + +#ifdef CONFIG_ARM_MODULE_PLTS + if (!new) { + struct module *mod = rec->arch.mod; + + if (mod) { + aaddr = get_module_plt(mod, ip, aaddr); + new = ftrace_call_replace(ip, aaddr); + } + } +#endif return ftrace_modify_code(rec->ip, old, new, true); } @@ -199,20 +224,39 @@ int ftrace_make_nop(struct module *mod, unsigned long new; int ret; - old = ftrace_call_replace(ip, adjust_address(rec, addr)); - new = ftrace_nop_replace(rec); - ret = ftrace_modify_code(ip, old, new, true); +#ifdef CONFIG_ARM_MODULE_PLTS + /* mod is only supplied during module loading */ + if (!mod) + mod = rec->arch.mod; + else + rec->arch.mod = mod; +#endif -#ifdef CONFIG_OLD_MCOUNT - if (ret == -EINVAL && addr == MCOUNT_ADDR) { - rec->arch.old_mcount = true; + for (;;) { + unsigned long aaddr = adjust_address(rec, addr); + + old = ftrace_call_replace(ip, aaddr); + +#ifdef CONFIG_ARM_MODULE_PLTS + if (!old && mod) { + aaddr = get_module_plt(mod, ip, aaddr); + old = ftrace_call_replace(ip, aaddr); + } +#endif - old = ftrace_call_replace(ip, adjust_address(rec, addr)); new = ftrace_nop_replace(rec); ret = ftrace_modify_code(ip, old, new, true); - } + +#ifdef CONFIG_OLD_MCOUNT + if (ret == -EINVAL && !rec->arch.old_mcount) { + rec->arch.old_mcount = true; + continue; + } #endif + break; + } + return ret; } diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c index f272711..0951270 100644 --- a/arch/arm/kernel/module-plts.c +++ b/arch/arm/kernel/module-plts.c @@ -7,6 +7,7 @@ */ #include <linux/elf.h> +#include <linux/ftrace.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/sort.h> @@ -22,18 +23,54 @@ (PLT_ENT_STRIDE - 8)) #endif +static const u32 fixed_plts[] = { +#ifdef CONFIG_FUNCTION_TRACER + FTRACE_ADDR, + MCOUNT_ADDR, +#ifdef CONFIG_OLD_MCOUNT + (unsigned long)ftrace_caller_old, + (unsigned long)mcount, +#endif +#endif +}; + static bool in_init(const struct module *mod, unsigned long loc) { return loc - (u32)mod->init_layout.base < mod->init_layout.size; } +static void prealloc_fixed(struct mod_plt_sec *pltsec, struct plt_entries *plt) +{ + int i; + + if (!ARRAY_SIZE(fixed_plts)) + return; + + for (i = 0; i < ARRAY_SIZE(plt->ldr); ++i) + plt->ldr[i] = PLT_ENT_LDR; + memcpy(plt->lit, fixed_plts, sizeof(fixed_plts)); + pltsec->plt_count = ARRAY_SIZE(fixed_plts); +} + u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) { struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : &mod->arch.init; + struct plt_entries *plt; + int idx; - struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr; - int idx = 0; + /* cache the address, ELF header is available only during module load */ + if (!pltsec->plt_ent) + pltsec->plt_ent = (struct plt_entries *)pltsec->plt->sh_addr; + plt = pltsec->plt_ent; + + if (!pltsec->plt_count) + prealloc_fixed(pltsec, plt); + + idx = ARRAY_SIZE(fixed_plts); + while (idx) + if (plt->lit[--idx] == val) + return (u32)&plt->ldr[idx]; /* * Look for an existing entry pointing to 'val'. Given that the @@ -182,8 +219,8 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { - unsigned long core_plts = 0; - unsigned long init_plts = 0; + unsigned long core_plts = ARRAY_SIZE(fixed_plts); + unsigned long init_plts = ARRAY_SIZE(fixed_plts); Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; Elf32_Sym *syms = NULL; @@ -238,6 +275,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.core.plt->sh_size = round_up(core_plts * PLT_ENT_SIZE, sizeof(struct plt_entries)); mod->arch.core.plt_count = 0; + mod->arch.core.plt_ent = NULL; mod->arch.init.plt->sh_type = SHT_NOBITS; mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; @@ -245,6 +283,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.init.plt->sh_size = round_up(init_plts * PLT_ENT_SIZE, sizeof(struct plt_entries)); mod->arch.init.plt_count = 0; + mod->arch.init.plt_ent = NULL; pr_debug("%s: plt=%x, init.plt=%x\n", __func__, mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size); -- 2.4.6
| |