ftrace: Check against is_kernel_text() instead of kaslr_offset()

As kaslr_offset() is architecture dependent and also may not be defined by
all architectures, when zeroing out unused weak functions, do not check
against kaslr_offset(), but instead check if the address is within the
kernel text sections. If KASLR added a shift to the zeroed out function,
it would still not be located in the kernel text. This is a more robust
way to test if the text is valid or not.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: "Arnd Bergmann" <arnd@arndb.de>
Link: https://lore.kernel.org/20250225182054.471759017@goodmis.org
Fixes: ef378c3b8233 ("scripts/sorttable: Zero out weak functions in mcount_loc table")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Mark Brown <broonie@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/all/20250224180805.GA1536711@ax162/
Closes: https://lore.kernel.org/all/5225b07b-a9b2-4558-9d5f-aa60b19f6317@sirena.org.uk/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 183f72cf15ed6a4e6c4ba7311d57e5cd3072045a..bec7b5dbdb3b46bffe32da72248f8a73dcf97750 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7004,7 +7004,6 @@ static int ftrace_process_locs(struct module *mod,
        unsigned long count;
        unsigned long *p;
        unsigned long addr;
-       unsigned long kaslr;
        unsigned long flags = 0; /* Shut up gcc */
        unsigned long pages;
        int ret = -ENOMEM;
@@ -7056,9 +7055,6 @@ static int ftrace_process_locs(struct module *mod,
                ftrace_pages->next = start_pg;
        }
 
-       /* For zeroed locations that were shifted for core kernel */
-       kaslr = !mod ? kaslr_offset() : 0;
-
        p = start;
        pg = start_pg;
        while (p < end) {
@@ -7072,7 +7068,18 @@ static int ftrace_process_locs(struct module *mod,
                 * object files to satisfy alignments.
                 * Skip any NULL pointers.
                 */
-               if (!addr || addr == kaslr) {
+               if (!addr) {
+                       skipped++;
+                       continue;
+               }
+
+               /*
+                * If this is core kernel, make sure the address is in core
+                * or inittext, as weak functions get zeroed and KASLR can
+                * move them to something other than zero. It just will not
+                * move it to an area where kernel text is.
+                */
+               if (!mod && !(is_kernel_text(addr) || is_kernel_inittext(addr))) {
                        skipped++;
                        continue;
                }