diff options
| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2017-11-20 20:41:30 +0300 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2017-12-01 16:04:59 +0300 |
| commit | be0f272bfc83797f70d44faca86954df62e2bbc0 (patch) | |
| tree | cc30988986ef959c80ad89912f5dc342f99f0be5 /arch/arm64/kernel/module-plts.c | |
| parent | 7e8b9c1d2e2f5f45db7d40b50d14f606097c25de (diff) | |
| download | linux-be0f272bfc83797f70d44faca86954df62e2bbc0.tar.xz | |
arm64: ftrace: emit ftrace-mod.o contents through code
When building the arm64 kernel with both CONFIG_ARM64_MODULE_PLTS and
CONFIG_DYNAMIC_FTRACE enabled, the ftrace-mod.o object file is built
with the kernel and contains a trampoline that is linked into each
module, so that modules can be loaded far away from the kernel and
still reach the ftrace entry point in the core kernel with an ordinary
relative branch, as is emitted by the compiler instrumentation code
dynamic ftrace relies on.
In order to be able to build out of tree modules, this object file
needs to be included into the linux-headers or linux-devel packages,
which is undesirable, as it makes arm64 a special case (although a
precedent does exist for 32-bit PPC).
Given that the trampoline essentially consists of a PLT entry, let's
not bother with a source or object file for it, and simply patch it
in whenever the trampoline is being populated, using the existing
PLT support routines.
Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/module-plts.c')
| -rw-r--r-- | arch/arm64/kernel/module-plts.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c index ebff6c155cac..ea640f92fe5a 100644 --- a/arch/arm64/kernel/module-plts.c +++ b/arch/arm64/kernel/module-plts.c @@ -120,6 +120,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, unsigned long core_plts = 0; unsigned long init_plts = 0; Elf64_Sym *syms = NULL; + Elf_Shdr *tramp = NULL; int i; /* @@ -131,6 +132,10 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.core.plt = sechdrs + i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt")) mod->arch.init.plt = sechdrs + i; + else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) && + !strcmp(secstrings + sechdrs[i].sh_name, + ".text.ftrace_trampoline")) + tramp = sechdrs + i; else if (sechdrs[i].sh_type == SHT_SYMTAB) syms = (Elf64_Sym *)sechdrs[i].sh_addr; } @@ -181,5 +186,12 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.init.plt_num_entries = 0; mod->arch.init.plt_max_entries = init_plts; + if (tramp) { + tramp->sh_type = SHT_NOBITS; + tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + tramp->sh_addralign = __alignof__(struct plt_entry); + tramp->sh_size = sizeof(struct plt_entry); + } + return 0; } |