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author | Steven Rostedt <srostedt@redhat.com> | 2008-11-15 01:21:20 +0100 |
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committer | Steven Rostedt <srostedt@redhat.com> | 2008-11-20 19:52:04 +0100 |
commit | e4486fe316895e87672a563c4f36393218f84ff1 (patch) | |
tree | 8cb8e68228e9a9a7c6acf8455d79b3484c8a78a4 /arch/powerpc/kernel/ftrace.c | |
parent | powerpc: ftrace, convert to new dynamic ftrace arch API (diff) | |
download | linux-e4486fe316895e87672a563c4f36393218f84ff1.tar.xz linux-e4486fe316895e87672a563c4f36393218f84ff1.zip |
powerpc: ftrace, use probe_kernel API to modify code
Impact: use cleaner probe_kernel API over assembly
Using probe_kernel_read/write interface is a much cleaner approach
than the current assembly version.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Diffstat (limited to 'arch/powerpc/kernel/ftrace.c')
-rw-r--r-- | arch/powerpc/kernel/ftrace.c | 53 |
1 files changed, 21 insertions, 32 deletions
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c index 24c023a5cae8..1adfbb268d8e 100644 --- a/arch/powerpc/kernel/ftrace.c +++ b/arch/powerpc/kernel/ftrace.c @@ -9,6 +9,7 @@ #include <linux/spinlock.h> #include <linux/hardirq.h> +#include <linux/uaccess.h> #include <linux/ftrace.h> #include <linux/percpu.h> #include <linux/init.h> @@ -72,45 +73,33 @@ static int ftrace_modify_code(unsigned long ip, unsigned char *old_code, unsigned char *new_code) { - unsigned replaced; - unsigned old = *(unsigned *)old_code; - unsigned new = *(unsigned *)new_code; - int faulted = 0; + unsigned char replaced[MCOUNT_INSN_SIZE]; /* * Note: Due to modules and __init, code can * disappear and change, we need to protect against faulting - * as well as code changing. + * as well as code changing. We do this by using the + * probe_kernel_* functions. * * No real locking needed, this code is run through - * kstop_machine. + * kstop_machine, or before SMP starts. */ - asm volatile ( - "1: lwz %1, 0(%2)\n" - " cmpw %1, %5\n" - " bne 2f\n" - " stwu %3, 0(%2)\n" - "2:\n" - ".section .fixup, \"ax\"\n" - "3: li %0, 1\n" - " b 2b\n" - ".previous\n" - ".section __ex_table,\"a\"\n" - _ASM_ALIGN "\n" - _ASM_PTR "1b, 3b\n" - ".previous" - : "=r"(faulted), "=r"(replaced) - : "r"(ip), "r"(new), - "0"(faulted), "r"(old) - : "memory"); - - if (replaced != old && replaced != new) - faulted = 2; - - if (!faulted) - flush_icache_range(ip, ip + 8); - - return faulted; + + /* read the text we want to modify */ + if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE)) + return -EFAULT; + + /* Make sure it is what we expect it to be */ + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) + return -EINVAL; + + /* replace the text with the new text */ + if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE)) + return -EPERM; + + flush_icache_range(ip, ip + 8); + + return 0; } static int test_24bit_addr(unsigned long ip, unsigned long addr) |