module/ftrace: handle patchable-function-entry

When using patchable-function-entry, the compiler will record the
callsites into a section named "__patchable_function_entries" rather
than "__mcount_loc". Let's abstract this difference behind a new
FTRACE_CALLSITE_SECTION, so that architectures don't have to handle this
explicitly (e.g. with custom module linker scripts).

As parisc currently handles this explicitly, it is fixed up accordingly,
with its custom linker script removed. Since FTRACE_CALLSITE_SECTION is
only defined when DYNAMIC_FTRACE is selected, the parisc module loading
code is updated to only use the definition in that case. When
DYNAMIC_FTRACE is not selected, modules shouldn't have this section, so
this removes some redundant work in that case.

To make sure that this is keep up-to-date for modules and the main
kernel, a comment is added to vmlinux.lds.h, with the existing ifdeffery
simplified for legibility.

I built parisc generic-{32,64}bit_defconfig with DYNAMIC_FTRACE enabled,
and verified that the section made it into the .ko files for modules.

Signed-off-by: Mark Rutland <[email protected]>
Acked-by: Helge Deller <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Torsten Duwe <[email protected]>
Tested-by: Amit Daniel Kachhap <[email protected]>
Tested-by: Sven Schnelle <[email protected]>
Tested-by: Torsten Duwe <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James E.J. Bottomley <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: [email protected]

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index ac5f34993b53..1c50093e2ebe 100644
--- a/arch/parisc/kernel/module.c
+++ b/arch/parisc/kernel/module.c
@@ -43,6 +43,7 @@
 #include <linux/elf.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
+#include <linux/ftrace.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
 #include <linux/bug.h>
@@ -862,7 +863,7 @@ int module_finalize(const Elf_Ehdr *hdr,
 	const char *strtab = NULL;
 	const Elf_Shdr *s;
 	char *secstrings;
-	int err, symindex = -1;
+	int symindex = -1;
 	Elf_Sym *newptr, *oldptr;
 	Elf_Shdr *symhdr = NULL;
 #ifdef DEBUG
@@ -946,11 +947,13 @@ int module_finalize(const Elf_Ehdr *hdr,
 			/* patch .altinstructions */
 			apply_alternatives(aseg, aseg + s->sh_size, me->name);
 
+#ifdef CONFIG_DYNAMIC_FTRACE
 		/* For 32 bit kernels we're compiling modules with
 		 * -ffunction-sections so we must relocate the addresses in the
-		 *__mcount_loc section.
+		 *  ftrace callsite section.
 		 */
-		if (symindex != -1 && !strcmp(secname, "__mcount_loc")) {
+		if (symindex != -1 && !strcmp(secname, FTRACE_CALLSITE_SECTION)) {
+			int err;
 			if (s->sh_type == SHT_REL)
 				err = apply_relocate((Elf_Shdr *)sechdrs,
 							strtab, symindex,
@@ -962,6 +965,7 @@ int module_finalize(const Elf_Ehdr *hdr,
 			if (err)
 				return err;
 		}
+#endif
 	}
 	return 0;
 }