trace: conserve gd register

An UEFI application may change the value of the register that gd lives in.
But some of our functions like get_ticks() access this register. So we
have to set the gd register to the U-Boot value when entering a trace
point and set it back to the application value when exiting the trace
point.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/lib/trace.c b/lib/trace.c
index 9956442fefe6b422fb5b048f9aa039a0acb44aad..a13e5bf228b3889e89243278431d244187d97527 100644 (file)
--- a/lib/trace.c
+++ b/lib/trace.c
@@ -56,6 +56,49 @@ static inline uintptr_t __attribute__((no_instrument_function))
        return offset / FUNC_SITE_SIZE;
 }
 
+#ifdef CONFIG_EFI_LOADER
+
+/**
+ * trace_gd - the value of the gd register
+ */
+static volatile void *trace_gd;
+
+/**
+ * trace_save_gd() - save the value of the gd register
+ */
+static void __attribute__((no_instrument_function)) trace_save_gd(void)
+{
+       trace_gd = gd;
+}
+
+/**
+ * trace_swap_gd() - swap between U-Boot and application gd register value
+ *
+ * An UEFI application may change the value of the register that gd lives in.
+ * But some of our functions like get_ticks() access this register. So we
+ * have to set the gd register to the U-Boot value when entering a trace
+ * point and set it back to the application value when exiting the trace point.
+ */
+static void __attribute__((no_instrument_function)) trace_swap_gd(void)
+{
+       volatile void *temp_gd = trace_gd;
+
+       trace_gd = gd;
+       gd = temp_gd;
+}
+
+#else
+
+static void __attribute__((no_instrument_function)) trace_save_gd(void)
+{
+}
+
+static void __attribute__((no_instrument_function)) trace_swap_gd(void)
+{
+}
+
+#endif
+
 static void __attribute__((no_instrument_function)) add_ftrace(void *func_ptr,
                                void *caller, ulong flags)
 {
@@ -100,6 +143,7 @@ void __attribute__((no_instrument_function)) __cyg_profile_func_enter(
        if (trace_enabled) {
                int func;
 
+               trace_swap_gd();
                add_ftrace(func_ptr, caller, FUNCF_ENTRY);
                func = func_ptr_to_num(func_ptr);
                if (func < hdr->func_count) {
@@ -111,6 +155,7 @@ void __attribute__((no_instrument_function)) __cyg_profile_func_enter(
                hdr->depth++;
                if (hdr->depth > hdr->depth_limit)
                        hdr->max_depth = hdr->depth;
+               trace_swap_gd();
        }
 }
 
@@ -126,8 +171,10 @@ void __attribute__((no_instrument_function)) __cyg_profile_func_exit(
                void *func_ptr, void *caller)
 {
        if (trace_enabled) {
+               trace_swap_gd();
                add_ftrace(func_ptr, caller, FUNCF_EXIT);
                hdr->depth--;
+               trace_swap_gd();
        }
 }
 
@@ -284,6 +331,8 @@ int __attribute__((no_instrument_function)) trace_init(void *buff,
        size_t needed;
        int was_disabled = !trace_enabled;
 
+       trace_save_gd();
+
        if (!was_disabled) {
 #ifdef CONFIG_TRACE_EARLY
                char *end;