From d9af12b72bfe2a4efc1d347e0ac1c669b85dcea9 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 25 Nov 2008 06:39:18 -0800 Subject: [PATCH] powerpc: ftrace, fix cast aliasing and add code verification Impact: clean up and robustness addition This patch addresses the comments made by Paul Mackerras. It removes the type casting between unsigned int and unsigned char pointers, and replaces them with a use of all unsigned int. Verification that the jump is indeed made to a trampoline has also been added. Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/ftrace.c | 121 +++++++++++++++++++---------------- 1 file changed, 65 insertions(+), 56 deletions(-) diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c index 3271cd698e4c..ea454a004406 100644 --- a/arch/powerpc/kernel/ftrace.c +++ b/arch/powerpc/kernel/ftrace.c @@ -162,26 +162,25 @@ static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned char replaced[MCOUNT_INSN_SIZE * 2]; - unsigned int *op = (unsigned *)&replaced; - unsigned char jmp[8]; - unsigned long *ptr = (unsigned long *)&jmp; + unsigned int op; + unsigned int jmp[5]; + unsigned long ptr; unsigned long ip = rec->ip; unsigned long tramp; int offset; /* read where this goes */ - if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + if (probe_kernel_read(&op, (void *)ip, sizeof(int))) return -EFAULT; /* Make sure that that this is still a 24bit jump */ - if (!is_bl_op(*op)) { - printk(KERN_ERR "Not expected bl: opcode is %x\n", *op); + if (!is_bl_op(op)) { + printk(KERN_ERR "Not expected bl: opcode is %x\n", op); return -EINVAL; } /* lets find where the pointer goes */ - tramp = find_bl_target(ip, *op); + tramp = find_bl_target(ip, op); /* * On PPC64 the trampoline looks like: @@ -200,19 +199,25 @@ __ftrace_make_nop(struct module *mod, DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc); /* Find where the trampoline jumps to */ - if (probe_kernel_read(jmp, (void *)tramp, 8)) { + if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) { printk(KERN_ERR "Failed to read %lx\n", tramp); return -EFAULT; } - DEBUGP(" %08x %08x", - (unsigned)(*ptr >> 32), - (unsigned)*ptr); + DEBUGP(" %08x %08x", jmp[0], jmp[1]); - offset = (unsigned)jmp[2] << 24 | - (unsigned)jmp[3] << 16 | - (unsigned)jmp[6] << 8 | - (unsigned)jmp[7]; + /* verify that this is what we expect it to be */ + if (((jmp[0] & 0xffff0000) != 0x3d820000) || + ((jmp[1] & 0xffff0000) != 0x398c0000) || + (jmp[2] != 0xf8410028) || + (jmp[3] != 0xe96c0020) || + (jmp[4] != 0xe84c0028)) { + printk(KERN_ERR "Not a trampoline\n"); + return -EINVAL; + } + + offset = (unsigned)((unsigned short)jmp[0]) << 16 | + (unsigned)((unsigned short)jmp[1]); DEBUGP(" %x ", offset); @@ -225,13 +230,13 @@ __ftrace_make_nop(struct module *mod, return -EFAULT; } - DEBUGP(" %08x %08x\n", - (unsigned)(*ptr >> 32), - (unsigned)*ptr); + DEBUGP(" %08x %08x\n", jmp[0], jmp[1]); + + ptr = ((unsigned long)jmp[0] << 32) + jmp[1]; /* This should match what was called */ - if (*ptr != GET_ADDR(addr)) { - printk(KERN_ERR "addr does not match %lx\n", *ptr); + if (ptr != GET_ADDR(addr)) { + printk(KERN_ERR "addr does not match %lx\n", ptr); return -EINVAL; } @@ -240,11 +245,11 @@ __ftrace_make_nop(struct module *mod, * 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1) * This needs to be turned to a nop too. */ - if (probe_kernel_read(replaced, (void *)(ip+4), MCOUNT_INSN_SIZE)) + if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) return -EFAULT; - if (*op != 0xe8410028) { - printk(KERN_ERR "Next line is not ld! (%08x)\n", *op); + if (op != 0xe8410028) { + printk(KERN_ERR "Next line is not ld! (%08x)\n", op); return -EINVAL; } @@ -261,9 +266,9 @@ __ftrace_make_nop(struct module *mod, * ld r2,40(r1) * 1: */ - op[0] = 0x48000008; /* b +8 */ + op = 0x48000008; /* b +8 */ - if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE)) + if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE)) return -EPERM; return 0; @@ -274,46 +279,52 @@ static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned char replaced[MCOUNT_INSN_SIZE]; - unsigned int *op = (unsigned *)&replaced; - unsigned char jmp[8]; - unsigned int *ptr = (unsigned int *)&jmp; + unsigned int op; + unsigned int jmp[4]; unsigned long ip = rec->ip; unsigned long tramp; - int offset; - if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; /* Make sure that that this is still a 24bit jump */ - if (!is_bl_op(*op)) { - printk(KERN_ERR "Not expected bl: opcode is %x\n", *op); + if (!is_bl_op(op)) { + printk(KERN_ERR "Not expected bl: opcode is %x\n", op); return -EINVAL; } /* lets find where the pointer goes */ - tramp = find_bl_target(ip, *op); + tramp = find_bl_target(ip, op); /* * On PPC32 the trampoline looks like: - * lis r11,sym@ha - * addi r11,r11,sym@l - * mtctr r11 - * bctr + * 0x3d, 0x60, 0x00, 0x00 lis r11,sym@ha + * 0x39, 0x6b, 0x00, 0x00 addi r11,r11,sym@l + * 0x7d, 0x69, 0x03, 0xa6 mtctr r11 + * 0x4e, 0x80, 0x04, 0x20 bctr */ DEBUGP("ip:%lx jumps to %lx", ip, tramp); /* Find where the trampoline jumps to */ - if (probe_kernel_read(jmp, (void *)tramp, 8)) { + if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) { printk(KERN_ERR "Failed to read %lx\n", tramp); return -EFAULT; } - DEBUGP(" %08x %08x ", ptr[0], ptr[1]); + DEBUGP(" %08x %08x ", jmp[0], jmp[1]); - tramp = (ptr[1] & 0xffff) | - ((ptr[0] & 0xffff) << 16); + /* verify that this is what we expect it to be */ + if (((jmp[0] & 0xffff0000) != 0x3d600000) || + ((jmp[1] & 0xffff0000) != 0x396b0000) || + (jmp[2] != 0x7d6903a6) || + (jmp[3] != 0x4e800420)) { + printk(KERN_ERR "Not a trampoline\n"); + return -EINVAL; + } + + tramp = (jmp[1] & 0xffff) | + ((jmp[0] & 0xffff) << 16); if (tramp & 0x8000) tramp -= 0x10000; @@ -326,9 +337,9 @@ __ftrace_make_nop(struct module *mod, return -EINVAL; } - op[0] = PPC_NOP_INSTR; + op = PPC_NOP_INSTR; - if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE)) + if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE)) return -EPERM; return 0; @@ -384,13 +395,12 @@ int ftrace_make_nop(struct module *mod, static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - unsigned char replaced[MCOUNT_INSN_SIZE * 2]; - unsigned int *op = (unsigned *)&replaced; + unsigned int op[2]; unsigned long ip = rec->ip; unsigned long offset; /* read where this goes */ - if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE * 2)) + if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2)) return -EFAULT; /* @@ -425,7 +435,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) DEBUGP("write to %lx\n", rec->ip); - if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2)) + if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2)) return -EPERM; return 0; @@ -434,18 +444,17 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - unsigned char replaced[MCOUNT_INSN_SIZE]; - unsigned int *op = (unsigned *)&replaced; + unsigned int op; unsigned long ip = rec->ip; unsigned long offset; /* read where this goes */ - if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; /* It should be pointing to a nop */ - if (op[0] != PPC_NOP_INSTR) { - printk(KERN_ERR "Expected NOP but have %x\n", op[0]); + if (op != PPC_NOP_INSTR) { + printk(KERN_ERR "Expected NOP but have %x\n", op); return -EINVAL; } @@ -465,11 +474,11 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) } /* Set to "bl addr" */ - op[0] = branch_offset(offset); + op = branch_offset(offset); DEBUGP("write to %lx\n", rec->ip); - if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE)) + if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE)) return -EPERM; return 0;