mips/kernel/ftrace.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Code for replacing ftrace calls with jumps.
0004  *
0005  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
0006  * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
0007  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
0008  *
0009  * Thanks goes to Steven Rostedt for writing the original x86 version.
0010  */
0011
0012 #include <linux/uaccess.h>
0013 #include <linux/init.h>
0014 #include <linux/ftrace.h>
0015 #include <linux/syscalls.h>
0016
0017 #include <asm/asm.h>
0018 #include <asm/asm-offsets.h>
0019 #include <asm/cacheflush.h>
0020 #include <asm/syscall.h>
0021 #include <asm/uasm.h>
0022 #include <asm/unistd.h>
0023
0024 #include <asm-generic/sections.h>
0025
0026 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
0027 #define MCOUNT_OFFSET_INSNS 5
0028 #else
0029 #define MCOUNT_OFFSET_INSNS 4
0030 #endif
0031
0032 #ifdef CONFIG_DYNAMIC_FTRACE
0033
0034 /* Arch override because MIPS doesn't need to run this from stop_machine() */
0035 void arch_ftrace_update_code(int command)
0036 {
0037     ftrace_modify_all_code(command);
0038 }
0039
0040 #define JAL 0x0c000000      /* jump & link: ip --> ra, jump to target */
0041 #define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
0042 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
0043
0044 #define INSN_NOP 0x00000000 /* nop */
0045 #define INSN_JAL(addr)  \
0046     ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
0047
0048 static unsigned int insn_jal_ftrace_caller __read_mostly;
0049 static unsigned int insn_la_mcount[2] __read_mostly;
0050 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
0051
0052 static inline void ftrace_dyn_arch_init_insns(void)
0053 {
0054     u32 *buf;
0055     unsigned int v1;
0056
0057     /* la v1, _mcount */
0058     v1 = 3;
0059     buf = (u32 *)&insn_la_mcount[0];
0060     UASM_i_LA(&buf, v1, MCOUNT_ADDR);
0061
0062     /* jal (ftrace_caller + 8), jump over the first two instruction */
0063     buf = (u32 *)&insn_jal_ftrace_caller;
0064     uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
0065
0066 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
0067     /* j ftrace_graph_caller */
0068     buf = (u32 *)&insn_j_ftrace_graph_caller;
0069     uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
0070 #endif
0071 }
0072
0073 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
0074 {
0075     int faulted;
0076
0077     /* *(unsigned int *)ip = new_code; */
0078     safe_store_code(new_code, ip, faulted);
0079
0080     if (unlikely(faulted))
0081         return -EFAULT;
0082
0083     flush_icache_range(ip, ip + 8);
0084
0085     return 0;
0086 }
0087
0088 #ifndef CONFIG_64BIT
0089 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
0090                 unsigned int new_code2)
0091 {
0092     int faulted;
0093
0094     safe_store_code(new_code1, ip, faulted);
0095     if (unlikely(faulted))
0096         return -EFAULT;
0097
0098     ip += 4;
0099     safe_store_code(new_code2, ip, faulted);
0100     if (unlikely(faulted))
0101         return -EFAULT;
0102
0103     ip -= 4;
0104     flush_icache_range(ip, ip + 8);
0105
0106     return 0;
0107 }
0108
0109 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
0110                  unsigned int new_code2)
0111 {
0112     int faulted;
0113
0114     ip += 4;
0115     safe_store_code(new_code2, ip, faulted);
0116     if (unlikely(faulted))
0117         return -EFAULT;
0118
0119     ip -= 4;
0120     safe_store_code(new_code1, ip, faulted);
0121     if (unlikely(faulted))
0122         return -EFAULT;
0123
0124     flush_icache_range(ip, ip + 8);
0125
0126     return 0;
0127 }
0128 #endif
0129
0130 /*
0131  * The details about the calling site of mcount on MIPS
0132  *
0133  * 1. For kernel:
0134  *
0135  * move at, ra
0136  * jal _mcount      --> nop
0137  *  sub sp, sp, 8   --> nop  (CONFIG_32BIT)
0138  *
0139  * 2. For modules:
0140  *
0141  * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
0142  *
0143  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
0144  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
0145  * move at, ra
0146  * move $12, ra_address
0147  * jalr v1
0148  *  sub sp, sp, 8
0149  *                  1: offset = 5 instructions
0150  * 2.2 For the Other situations
0151  *
0152  * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
0153  * addiu v1, v1, low_16bit_of_mcount --> nop  (CONFIG_32BIT)
0154  * move at, ra
0155  * jalr v1
0156  *  nop | move $12, ra_address | sub sp, sp, 8
0157  *                  1: offset = 4 instructions
0158  */
0159
0160 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
0161
0162 int ftrace_make_nop(struct module *mod,
0163             struct dyn_ftrace *rec, unsigned long addr)
0164 {
0165     unsigned int new;
0166     unsigned long ip = rec->ip;
0167
0168     /*
0169      * If ip is in kernel space, no long call, otherwise, long call is
0170      * needed.
0171      */
0172     new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
0173 #ifdef CONFIG_64BIT
0174     return ftrace_modify_code(ip, new);
0175 #else
0176     /*
0177      * On 32 bit MIPS platforms, gcc adds a stack adjust
0178      * instruction in the delay slot after the branch to
0179      * mcount and expects mcount to restore the sp on return.
0180      * This is based on a legacy API and does nothing but
0181      * waste instructions so it's being removed at runtime.
0182      */
0183     return ftrace_modify_code_2(ip, new, INSN_NOP);
0184 #endif
0185 }
0186
0187 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
0188 {
0189     unsigned int new;
0190     unsigned long ip = rec->ip;
0191
0192     new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
0193
0194 #ifdef CONFIG_64BIT
0195     return ftrace_modify_code(ip, new);
0196 #else
0197     return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
0198                         INSN_NOP : insn_la_mcount[1]);
0199 #endif
0200 }
0201
0202 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
0203
0204 int ftrace_update_ftrace_func(ftrace_func_t func)
0205 {
0206     unsigned int new;
0207
0208     new = INSN_JAL((unsigned long)func);
0209
0210     return ftrace_modify_code(FTRACE_CALL_IP, new);
0211 }
0212
0213 int __init ftrace_dyn_arch_init(void)
0214 {
0215     /* Encode the instructions when booting */
0216     ftrace_dyn_arch_init_insns();
0217
0218     /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
0219     ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
0220
0221     return 0;
0222 }
0223 #endif  /* CONFIG_DYNAMIC_FTRACE */
0224
0225 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
0226
0227 #ifdef CONFIG_DYNAMIC_FTRACE
0228
0229 extern void ftrace_graph_call(void);
0230 #define FTRACE_GRAPH_CALL_IP    ((unsigned long)(&ftrace_graph_call))
0231
0232 int ftrace_enable_ftrace_graph_caller(void)
0233 {
0234     return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
0235             insn_j_ftrace_graph_caller);
0236 }
0237
0238 int ftrace_disable_ftrace_graph_caller(void)
0239 {
0240     return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
0241 }
0242
0243 #endif  /* CONFIG_DYNAMIC_FTRACE */
0244
0245 #ifndef KBUILD_MCOUNT_RA_ADDRESS
0246
0247 #define S_RA_SP (0xafbf << 16)  /* s{d,w} ra, offset(sp) */
0248 #define S_R_SP  (0xafb0 << 16)  /* s{d,w} R, offset(sp) */
0249 #define OFFSET_MASK 0xffff  /* stack offset range: 0 ~ PT_SIZE */
0250
0251 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
0252         old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
0253 {
0254     unsigned long sp, ip, tmp;
0255     unsigned int code;
0256     int faulted;
0257
0258     /*
0259      * For module, move the ip from the return address after the
0260      * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
0261      * kernel, move after the instruction "move ra, at"(offset is 16)
0262      */
0263     ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
0264
0265     /*
0266      * search the text until finding the non-store instruction or "s{d,w}
0267      * ra, offset(sp)" instruction
0268      */
0269     do {
0270         /* get the code at "ip": code = *(unsigned int *)ip; */
0271         safe_load_code(code, ip, faulted);
0272
0273         if (unlikely(faulted))
0274             return 0;
0275         /*
0276          * If we hit the non-store instruction before finding where the
0277          * ra is stored, then this is a leaf function and it does not
0278          * store the ra on the stack
0279          */
0280         if ((code & S_R_SP) != S_R_SP)
0281             return parent_ra_addr;
0282
0283         /* Move to the next instruction */
0284         ip -= 4;
0285     } while ((code & S_RA_SP) != S_RA_SP);
0286
0287     sp = fp + (code & OFFSET_MASK);
0288
0289     /* tmp = *(unsigned long *)sp; */
0290     safe_load_stack(tmp, sp, faulted);
0291     if (unlikely(faulted))
0292         return 0;
0293
0294     if (tmp == old_parent_ra)
0295         return sp;
0296     return 0;
0297 }
0298
0299 #endif  /* !KBUILD_MCOUNT_RA_ADDRESS */
0300
0301 /*
0302  * Hook the return address and push it in the stack of return addrs
0303  * in current thread info.
0304  */
0305 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
0306                unsigned long fp)
0307 {
0308     unsigned long old_parent_ra;
0309     unsigned long return_hooker = (unsigned long)
0310         &return_to_handler;
0311     int faulted, insns;
0312
0313     if (unlikely(ftrace_graph_is_dead()))
0314         return;
0315
0316     if (unlikely(atomic_read(&current->tracing_graph_pause)))
0317         return;
0318
0319     /*
0320      * "parent_ra_addr" is the stack address where the return address of
0321      * the caller of _mcount is saved.
0322      *
0323      * If gcc < 4.5, a leaf function does not save the return address
0324      * in the stack address, so we "emulate" one in _mcount's stack space,
0325      * and hijack it directly.
0326      * For a non-leaf function, it does save the return address to its own
0327      * stack space, so we can not hijack it directly, but need to find the
0328      * real stack address, which is done by ftrace_get_parent_addr().
0329      *
0330      * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
0331      * non-leaf function, the location of the return address will be saved
0332      * to $12 for us.
0333      * For a leaf function, it just puts a zero into $12, so we handle
0334      * it in ftrace_graph_caller() of mcount.S.
0335      */
0336
0337     /* old_parent_ra = *parent_ra_addr; */
0338     safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
0339     if (unlikely(faulted))
0340         goto out;
0341 #ifndef KBUILD_MCOUNT_RA_ADDRESS
0342     parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
0343             old_parent_ra, (unsigned long)parent_ra_addr, fp);
0344     /*
0345      * If fails when getting the stack address of the non-leaf function's
0346      * ra, stop function graph tracer and return
0347      */
0348     if (parent_ra_addr == NULL)
0349         goto out;
0350 #endif
0351     /* *parent_ra_addr = return_hooker; */
0352     safe_store_stack(return_hooker, parent_ra_addr, faulted);
0353     if (unlikely(faulted))
0354         goto out;
0355
0356     /*
0357      * Get the recorded ip of the current mcount calling site in the
0358      * __mcount_loc section, which will be used to filter the function
0359      * entries configured through the tracing/set_graph_function interface.
0360      */
0361
0362     insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
0363     self_ra -= (MCOUNT_INSN_SIZE * insns);
0364
0365     if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
0366         *parent_ra_addr = old_parent_ra;
0367     return;
0368 out:
0369     ftrace_graph_stop();
0370     WARN_ON(1);
0371 }
0372 #endif  /* CONFIG_FUNCTION_GRAPH_TRACER */
0373
0374 #ifdef CONFIG_FTRACE_SYSCALLS
0375
0376 #ifdef CONFIG_32BIT
0377 unsigned long __init arch_syscall_addr(int nr)
0378 {
0379     return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
0380 }
0381 #endif
0382
0383 #ifdef CONFIG_64BIT
0384
0385 unsigned long __init arch_syscall_addr(int nr)
0386 {
0387 #ifdef CONFIG_MIPS32_N32
0388     if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
0389         return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
0390 #endif
0391     if (nr >= __NR_64_Linux  && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
0392         return (unsigned long)sys_call_table[nr - __NR_64_Linux];
0393 #ifdef CONFIG_MIPS32_O32
0394     if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
0395         return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
0396 #endif
0397
0398     return (unsigned long) &sys_ni_syscall;
0399 }
0400 #endif
0401
0402 #endif /* CONFIG_FTRACE_SYSCALLS */