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| author | Will Deacon <will@kernel.org> | 2019-08-16 14:57:43 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2019-08-16 17:40:03 +0100 |
| commit | b6143d10d23ebb4a77af311e8b8b7f019d0163e6 (patch) | |
| tree | f2e7abeb246bc656dd7f1213b5b0e423fa0c4854 /arch | |
| parent | 5717fe5ab38f9ccb32718bcb03bea68409c9cce4 (diff) | |
| download | lwn-b6143d10d23ebb4a77af311e8b8b7f019d0163e6.tar.gz lwn-b6143d10d23ebb4a77af311e8b8b7f019d0163e6.zip | |
arm64: ftrace: Ensure module ftrace trampoline is coherent with I-side
The initial support for dynamic ftrace trampolines in modules made use
of an indirect branch which loaded its target from the beginning of
a special section (e71a4e1bebaf7 ("arm64: ftrace: add support for far
branches to dynamic ftrace")). Since no instructions were being patched,
no cache maintenance was needed. However, later in be0f272bfc83 ("arm64:
ftrace: emit ftrace-mod.o contents through code") this code was reworked
to output the trampoline instructions directly into the PLT entry but,
unfortunately, the necessary cache maintenance was overlooked.
Add a call to __flush_icache_range() after writing the new trampoline
instructions but before patching in the branch to the trampoline.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: James Morse <james.morse@arm.com>
Cc: <stable@vger.kernel.org>
Fixes: be0f272bfc83 ("arm64: ftrace: emit ftrace-mod.o contents through code")
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kernel/ftrace.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index 1285c7b2947f..171773257974 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -73,7 +73,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) if (offset < -SZ_128M || offset >= SZ_128M) { #ifdef CONFIG_ARM64_MODULE_PLTS - struct plt_entry trampoline; + struct plt_entry trampoline, *dst; struct module *mod; /* @@ -106,23 +106,27 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) * to check if the actual opcodes are in fact identical, * regardless of the offset in memory so use memcmp() instead. */ - trampoline = get_plt_entry(addr, mod->arch.ftrace_trampoline); - if (memcmp(mod->arch.ftrace_trampoline, &trampoline, - sizeof(trampoline))) { - if (plt_entry_is_initialized(mod->arch.ftrace_trampoline)) { + dst = mod->arch.ftrace_trampoline; + trampoline = get_plt_entry(addr, dst); + if (memcmp(dst, &trampoline, sizeof(trampoline))) { + if (plt_entry_is_initialized(dst)) { pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n"); return -EINVAL; } /* point the trampoline to our ftrace entry point */ module_disable_ro(mod); - *mod->arch.ftrace_trampoline = trampoline; + *dst = trampoline; module_enable_ro(mod, true); - /* update trampoline before patching in the branch */ - smp_wmb(); + /* + * Ensure updated trampoline is visible to instruction + * fetch before we patch in the branch. + */ + __flush_icache_range((unsigned long)&dst[0], + (unsigned long)&dst[1]); } - addr = (unsigned long)(void *)mod->arch.ftrace_trampoline; + addr = (unsigned long)dst; #else /* CONFIG_ARM64_MODULE_PLTS */ return -EINVAL; #endif /* CONFIG_ARM64_MODULE_PLTS */ |