From 215828067f921b6765d194e740695f4b0f68f628 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 3 Feb 2017 09:54:05 +0000 Subject: [PATCH] kbuild: modversions: add infrastructure for emitting relative CRCs This add the kbuild infrastructure that will allow architectures to emit vmlinux symbol CRCs as 32-bit offsets to another location in the kernel where the actual value is stored. This works around problems with CRCs being mistaken for relocatable symbols on kernels that self relocate at runtime (i.e., powerpc with CONFIG_RELOCATABLE=y) For the kbuild side of things, this comes down to the following: - introducing a Kconfig symbol MODULE_REL_CRCS - adding a -R switch to genksyms to instruct it to emit the CRC symbols as references into the .rodata section - making modpost distinguish such references from absolute CRC symbols by the section index (SHN_ABS) - making kallsyms disregard non-absolute symbols with a __crc_ prefix Signed-off-by: Ard Biesheuvel Signed-off-by: Linus Torvalds --- init/Kconfig | 4 ++++ scripts/Makefile.build | 2 ++ scripts/genksyms/genksyms.c | 19 ++++++++++++++----- scripts/kallsyms.c | 12 ++++++++++++ scripts/mod/modpost.c | 10 ++++++++++ 5 files changed, 42 insertions(+), 5 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index e1a937348a3ed..4dd8bd232a1d4 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1987,6 +1987,10 @@ config MODVERSIONS make them incompatible with the kernel you are running. If unsure, say N. +config MODULE_REL_CRCS + bool + depends on MODVERSIONS + config MODULE_SRCVERSION_ALL bool "Source checksum for all modules" help diff --git a/scripts/Makefile.build b/scripts/Makefile.build index eadcd4d359d91..d883116ebaa45 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -164,6 +164,7 @@ cmd_gensymtypes_c = \ $(CPP) -D__GENKSYMS__ $(c_flags) $< | \ $(GENKSYMS) $(if $(1), -T $(2)) \ $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \ + $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \ $(if $(KBUILD_PRESERVE),-p) \ -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null)) @@ -337,6 +338,7 @@ cmd_gensymtypes_S = \ $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \ $(GENKSYMS) $(if $(1), -T $(2)) \ $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \ + $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS)) \ $(if $(KBUILD_PRESERVE),-p) \ -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null)) diff --git a/scripts/genksyms/genksyms.c b/scripts/genksyms/genksyms.c index 06121ce524a76..c9235d8340f1e 100644 --- a/scripts/genksyms/genksyms.c +++ b/scripts/genksyms/genksyms.c @@ -44,7 +44,7 @@ char *cur_filename, *source_file; int in_source_file; static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types, - flag_preserve, flag_warnings; + flag_preserve, flag_warnings, flag_rel_crcs; static const char *mod_prefix = ""; static int errors; @@ -693,7 +693,10 @@ void export_symbol(const char *name) fputs(">\n", debugfile); /* Used as a linker script. */ - printf("%s__crc_%s = 0x%08lx ;\n", mod_prefix, name, crc); + printf(!flag_rel_crcs ? "%s__crc_%s = 0x%08lx;\n" : + "SECTIONS { .rodata : ALIGN(4) { " + "%s__crc_%s = .; LONG(0x%08lx); } }\n", + mod_prefix, name, crc); } } @@ -730,7 +733,7 @@ void error_with_pos(const char *fmt, ...) static void genksyms_usage(void) { - fputs("Usage:\n" "genksyms [-adDTwqhV] > /path/to/.tmp_obj.ver\n" "\n" + fputs("Usage:\n" "genksyms [-adDTwqhVR] > /path/to/.tmp_obj.ver\n" "\n" #ifdef __GNU_LIBRARY__ " -s, --symbol-prefix Select symbol prefix\n" " -d, --debug Increment the debug level (repeatable)\n" @@ -742,6 +745,7 @@ static void genksyms_usage(void) " -q, --quiet Disable warnings (default)\n" " -h, --help Print this message\n" " -V, --version Print the release version\n" + " -R, --relative-crc Emit section relative symbol CRCs\n" #else /* __GNU_LIBRARY__ */ " -s Select symbol prefix\n" " -d Increment the debug level (repeatable)\n" @@ -753,6 +757,7 @@ static void genksyms_usage(void) " -q Disable warnings (default)\n" " -h Print this message\n" " -V Print the release version\n" + " -R Emit section relative symbol CRCs\n" #endif /* __GNU_LIBRARY__ */ , stderr); } @@ -774,13 +779,14 @@ int main(int argc, char **argv) {"preserve", 0, 0, 'p'}, {"version", 0, 0, 'V'}, {"help", 0, 0, 'h'}, + {"relative-crc", 0, 0, 'R'}, {0, 0, 0, 0} }; - while ((o = getopt_long(argc, argv, "s:dwqVDr:T:ph", + while ((o = getopt_long(argc, argv, "s:dwqVDr:T:phR", &long_opts[0], NULL)) != EOF) #else /* __GNU_LIBRARY__ */ - while ((o = getopt(argc, argv, "s:dwqVDr:T:ph")) != EOF) + while ((o = getopt(argc, argv, "s:dwqVDr:T:phR")) != EOF) #endif /* __GNU_LIBRARY__ */ switch (o) { case 's': @@ -823,6 +829,9 @@ int main(int argc, char **argv) case 'h': genksyms_usage(); return 0; + case 'R': + flag_rel_crcs = 1; + break; default: genksyms_usage(); return 1; diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 299b92ca1ae09..5d554419170b7 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -219,6 +219,10 @@ static int symbol_valid(struct sym_entry *s) "_SDA2_BASE_", /* ppc */ NULL }; + static char *special_prefixes[] = { + "__crc_", /* modversions */ + NULL }; + static char *special_suffixes[] = { "_veneer", /* arm */ "_from_arm", /* arm */ @@ -259,6 +263,14 @@ static int symbol_valid(struct sym_entry *s) if (strcmp(sym_name, special_symbols[i]) == 0) return 0; + for (i = 0; special_prefixes[i]; i++) { + int l = strlen(special_prefixes[i]); + + if (l <= strlen(sym_name) && + strncmp(sym_name, special_prefixes[i], l) == 0) + return 0; + } + for (i = 0; special_suffixes[i]; i++) { int l = strlen(sym_name) - strlen(special_suffixes[i]); diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 29c89a6bad3d3..4dedd0d3d3a7f 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -621,6 +621,16 @@ static void handle_modversions(struct module *mod, struct elf_info *info, if (strncmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) { is_crc = true; crc = (unsigned int) sym->st_value; + if (sym->st_shndx != SHN_UNDEF && sym->st_shndx != SHN_ABS) { + unsigned int *crcp; + + /* symbol points to the CRC in the ELF object */ + crcp = (void *)info->hdr + sym->st_value + + info->sechdrs[sym->st_shndx].sh_offset - + (info->hdr->e_type != ET_REL ? + info->sechdrs[sym->st_shndx].sh_addr : 0); + crc = *crcp; + } sym_update_crc(symname + strlen(CRC_PFX), mod, crc, export); } -- 2.39.5