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arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels 

When a kernel is built without CONFIG_ARM64_MODULE_PLTS, we don't
generate the expected branch instruction in ftrace_make_nop(). This
means we pass zero (rather than a valid branch) to ftrace_modify_code()
as the expected instruction to validate. This causes us to return
-EINVAL to the core ftrace code for a valid case, resulting in a splat
at boot time.

This was an unintended effect of commit:

  687644209a ("arm64: ftrace: fix building without CONFIG_MODULES")

... which incorrectly moved the generation of the branch instruction
into the ifdef for CONFIG_ARM64_MODULE_PLTS.

This patch fixes the issue by moving the ifdef inside of the relevant
if-else case, and always checking that the branch is in range,
regardless of CONFIG_ARM64_MODULE_PLTS. This ensures that we generate
the expected branch instruction, and also improves our sanity checks.

For consistency, both ftrace_make_nop() and ftrace_make_call() are
updated with this pattern.

Fixes: 687644209a ("arm64: ftrace: fix building without CONFIG_MODULES")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2017-06-23 18:02:06 +01:00 committed by Will Deacon
parent 33f082614c
commit 8486e54d30
1 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
arch/arm64/kernel/ftrace.c
View File

@ -72,11 +72,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long pc = rec->ip;
u32 old, new;
#ifdef CONFIG_ARM64_MODULE_PLTS
long offset = (long)pc - (long)addr;
if (offset < -SZ_128M || offset >= SZ_128M) {
#ifdef CONFIG_ARM64_MODULE_PLTS
unsigned long *trampoline;
struct module *mod;
@ -121,8 +120,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
smp_wmb();
}
addr = (unsigned long)&trampoline[1];
}
#else /* CONFIG_ARM64_MODULE_PLTS */
return -EINVAL;
#endif /* CONFIG_ARM64_MODULE_PLTS */
}
old = aarch64_insn_gen_nop();
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
@ -139,11 +140,10 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long pc = rec->ip;
bool validate = true;
u32 old = 0, new;
#ifdef CONFIG_ARM64_MODULE_PLTS
long offset = (long)pc - (long)addr;
if (offset < -SZ_128M || offset >= SZ_128M) {
#ifdef CONFIG_ARM64_MODULE_PLTS
u32 replaced;
/*
@ -176,11 +176,13 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
return -EINVAL;
validate = false;
#else /* CONFIG_ARM64_MODULE_PLTS */
return -EINVAL;
#endif /* CONFIG_ARM64_MODULE_PLTS */
} else {
old = aarch64_insn_gen_branch_imm(pc, addr,
AARCH64_INSN_BRANCH_LINK);
}
#endif /* CONFIG_ARM64_MODULE_PLTS */
new = aarch64_insn_gen_nop();