[PATCH 4/4] ACPI / sysfs: Add support to allow leading "\" missing in trace_method_name.

[Lv Zheng]

Since _SB.PCI0 can be used as relative path from root and can be easily
converted into internal trace_method_name format, we allow users to specify
trace_method_name using relative paths from root.
Note this is useful for grub2 for which users failed to pass "\" from the
grub configuration file.

Signed-off-by: Lv Zheng <lv.zh...@intel.com>
---
 drivers/acpi/sysfs.c |   28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index 8979e4a..40a4265 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -164,14 +164,18 @@ static const struct kernel_param_ops 
param_ops_debug_level = {
 module_param_cb(debug_layer, &param_ops_debug_layer, &acpi_dbg_layer, 0644);
 module_param_cb(debug_level, &param_ops_debug_level, &acpi_dbg_level, 0644);
 
-static char* trace_method_name;
-static bool trace_method_kmalloced;
+static char trace_method_name[1024];
 
 int param_set_trace_method_name(const char *val, const struct kernel_param *kp)
 {
        u32 saved_flags = 0;
+       bool is_abs_path = true;
 
-       if (strlen(val) > 1024) {
+       if (*val != '\\')
+               is_abs_path = false;
+
+       if ((is_abs_path && strlen(val) > 1023) ||
+           (!is_abs_path && strlen(val) > 1022)) {
                pr_err("%s: string parameter too long\n", kp->name);
                return -ENOSPC;
        }
@@ -187,19 +191,13 @@ int param_set_trace_method_name(const char *val, const 
struct kernel_param *kp)
                               acpi_gbl_trace_dbg_layer,
                               0);
 
-       if (trace_method_kmalloced)
-               kfree(trace_method_name);
-       trace_method_name = NULL;
-       trace_method_kmalloced = false;
-
        /* This is a hack.  We can't kmalloc in early boot. */
-       if (slab_is_available()) {
-               trace_method_name = kstrdup(val, GFP_KERNEL);
-               if (!trace_method_name)
-                       return -ENOMEM;
-               trace_method_kmalloced = true;
-       } else
-               trace_method_name = (char *)val;
+       if (is_abs_path)
+               strcpy(trace_method_name, val);
+       else {
+               trace_method_name[0] = '\\';
+               strcpy(trace_method_name+1, val);
+       }
 
        /* Restore the original tracer state */
        (void)acpi_debug_trace(trace_method_name,
-- 
1.7.10

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