From dc283d7037555aa6891188719be2f1b4af9535c9 Mon Sep 17 00:00:00 2001 From: Rabin Vincent Date: Wed, 29 Feb 2012 15:59:07 +0100 Subject: [PATCH 1/1] ARM: 7351/1: ftrace: remove useless memory checks Before replacing an instruction, the ftrace code determines what the old instruction should be and verifies that that's what's really there in memory before replacing it. This is useful if for example a bug in mcountrecord causes it to record wrong locations. However, in cases where we replace call sites in entry-common.S, these checks are not needed. For these, we currently just memcpy() the memory content and then "verify" it -- this is quite useless and can be removed. Signed-off-by: Rabin Vincent Signed-off-by: Russell King --- arch/arm/kernel/ftrace.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index c0062ad1e847..6fd7c4a1e532 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -121,15 +121,17 @@ static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) } static int ftrace_modify_code(unsigned long pc, unsigned long old, - unsigned long new) + unsigned long new, bool validate) { unsigned long replaced; - if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) - return -EFAULT; + if (validate) { + if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) + return -EFAULT; - if (replaced != old) - return -EINVAL; + if (replaced != old) + return -EINVAL; + } if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) return -EPERM; @@ -141,23 +143,21 @@ static int ftrace_modify_code(unsigned long pc, unsigned long old, int ftrace_update_ftrace_func(ftrace_func_t func) { - unsigned long pc, old; + unsigned long pc; unsigned long new; int ret; pc = (unsigned long)&ftrace_call; - memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE); new = ftrace_call_replace(pc, (unsigned long)func); - ret = ftrace_modify_code(pc, old, new); + ret = ftrace_modify_code(pc, 0, new, false); #ifdef CONFIG_OLD_MCOUNT if (!ret) { pc = (unsigned long)&ftrace_call_old; - memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE); new = ftrace_call_replace(pc, (unsigned long)func); - ret = ftrace_modify_code(pc, old, new); + ret = ftrace_modify_code(pc, 0, new, false); } #endif @@ -172,7 +172,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) old = ftrace_nop_replace(rec); new = ftrace_call_replace(ip, adjust_address(rec, addr)); - return ftrace_modify_code(rec->ip, old, new); + return ftrace_modify_code(rec->ip, old, new, true); } int ftrace_make_nop(struct module *mod, @@ -185,7 +185,7 @@ int ftrace_make_nop(struct module *mod, old = ftrace_call_replace(ip, adjust_address(rec, addr)); new = ftrace_nop_replace(rec); - ret = ftrace_modify_code(ip, old, new); + ret = ftrace_modify_code(ip, old, new, true); #ifdef CONFIG_OLD_MCOUNT if (ret == -EINVAL && addr == MCOUNT_ADDR) { @@ -193,7 +193,7 @@ int ftrace_make_nop(struct module *mod, old = ftrace_call_replace(ip, adjust_address(rec, addr)); new = ftrace_nop_replace(rec); - ret = ftrace_modify_code(ip, old, new); + ret = ftrace_modify_code(ip, old, new, true); } #endif @@ -254,7 +254,7 @@ static int __ftrace_modify_caller(unsigned long *callsite, unsigned long old = enable ? nop : branch; unsigned long new = enable ? branch : nop; - return ftrace_modify_code(pc, old, new); + return ftrace_modify_code(pc, old, new, true); } static int ftrace_modify_graph_caller(bool enable) -- 2.20.1