module/ftrace: handle patchable-function-entry

BugLink: https://bugs.launchpad.net/bugs/1967582
commit a1326b17ac03a9012cb3d01e434aacb4d67a416c upstream.

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 <mark.rutland@arm.com>
Acked-by: Helge Deller <deller@gmx.de>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Sven Schnelle <svens@stackframe.org>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: linux-parisc@vger.kernel.org
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/parisc/Makefile b/arch/parisc/Makefile
index caa90ae0b4acccf7e9cc580569019f61854e189a..04460c2d2f8c153c99c2cbdaa7fbf893dd373355 100644 (file)
--- a/arch/parisc/Makefile
+++ b/arch/parisc/Makefile
@@ -65,7 +65,6 @@ KBUILD_CFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY=1 \
                 -DFTRACE_PATCHABLE_FUNCTION_SIZE=$(NOP_COUNT)
 
 CC_FLAGS_FTRACE := -fpatchable-function-entry=$(NOP_COUNT),$(shell echo $$(($(NOP_COUNT)-1)))
-KBUILD_LDS_MODULE += $(srctree)/arch/parisc/kernel/module.lds
 endif
 
 OBJCOPY_FLAGS =-O binary -R .note -R .comment -S

diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index ac5f34993b53bb7c42341aef529ab459fb58fd6f..1c50093e2ebeef3ad832533dffa4edcd3a6b59a5 100644 (file)
--- 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;
 }

diff --git a/arch/parisc/kernel/module.lds b/arch/parisc/kernel/module.lds
deleted file mode 100644 (file)
index 1a9a92a..0000000
--- a/arch/parisc/kernel/module.lds
+++ /dev/null
@@ -1,7 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-SECTIONS {
-       __mcount_loc : {
-               *(__patchable_function_entries)
-       }
-}

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8a5ced9cf527333617dba3840e52855815b8aef7..77d4281815579a73619e22b98b68c7b5887d265e 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -110,17 +110,17 @@
 #endif
 
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
-#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY
-#define MCOUNT_REC()   . = ALIGN(8);                           \
-                       __start_mcount_loc = .;                 \
-                       KEEP(*(__patchable_function_entries))   \
-                       __stop_mcount_loc = .;
-#else
+/*
+ * The ftrace call sites are logged to a section whose name depends on the
+ * compiler option used. A given kernel image will only use one, AKA
+ * FTRACE_CALLSITE_SECTION. We capture all of them here to avoid header
+ * dependencies for FTRACE_CALLSITE_SECTION's definition.
+ */
 #define MCOUNT_REC()   . = ALIGN(8);                           \
                        __start_mcount_loc = .;                 \
                        KEEP(*(__mcount_loc))                   \
+                       KEEP(*(__patchable_function_entries))   \
                        __stop_mcount_loc = .;
-#endif
 #else
 #define MCOUNT_REC()
 #endif

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9867d90d635e06bb3bbdb6804e27795220abeb3a..9141f22632864d9814cabe4e7544b6401fc4cf4a 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -738,6 +738,11 @@ static inline unsigned long get_lock_parent_ip(void)
 
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 extern void ftrace_init(void);
+#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY
+#define FTRACE_CALLSITE_SECTION        "__patchable_function_entries"
+#else
+#define FTRACE_CALLSITE_SECTION        "__mcount_loc"
+#endif
 #else
 static inline void ftrace_init(void) { }
 #endif

diff --git a/kernel/module.c b/kernel/module.c
index 7ab5e0731d2eee1ac67aed24a96612c5503a0661..100291c0ab3a50257620365a1caa109eed1142e3 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3349,7 +3349,7 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 #endif
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
        /* sechdrs[0].sh_size is always zero */
-       mod->ftrace_callsites = section_objs(info, "__mcount_loc",
+       mod->ftrace_callsites = section_objs(info, FTRACE_CALLSITE_SECTION,
                                             sizeof(*mod->ftrace_callsites),
                                             &mod->num_ftrace_callsites);
 #endif