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authorMarc Zyngier <maz@kernel.org>2019-08-24 14:12:31 +0100
committerWill Deacon <will@kernel.org>2019-08-27 16:19:56 +0100
commit2a1a3fa0f29270583f0e6e3100d609e09697add1 (patch)
tree897e0b27d642687982cb5ca1c3e7228416ccbcec /kernel
parentb6143d10d23ebb4a77af311e8b8b7f019d0163e6 (diff)
kallsyms: Don't let kallsyms_lookup_size_offset() fail on retrieving the first symbol
An arm64 kernel configured with CONFIG_KPROBES=y CONFIG_KALLSYMS=y # CONFIG_KALLSYMS_ALL is not set CONFIG_KALLSYMS_BASE_RELATIVE=y reports the following kprobe failure: [ 0.032677] kprobes: failed to populate blacklist: -22 [ 0.033376] Please take care of using kprobes. It appears that kprobe fails to retrieve the symbol at address 0xffff000010081000, despite this symbol being in System.map: ffff000010081000 T __exception_text_start This symbol is part of the first group of aliases in the kallsyms_offsets array (symbol names generated using ugly hacks in scripts/kallsyms.c): kallsyms_offsets: .long 0x1000 // do_undefinstr .long 0x1000 // efi_header_end .long 0x1000 // _stext .long 0x1000 // __exception_text_start .long 0x12b0 // do_cp15instr Looking at the implementation of get_symbol_pos(), it returns the lowest index for aliasing symbols. In this case, it return 0. But kallsyms_lookup_size_offset() considers 0 as a failure, which is obviously wrong (there is definitely a valid symbol living there). In turn, the kprobe blacklisting stops abruptly, hence the original error. A CONFIG_KALLSYMS_ALL kernel wouldn't fail as there is always some random symbols at the beginning of this array, which are never looked up via kallsyms_lookup_size_offset. Fix it by considering that get_symbol_pos() is always successful (which is consistent with the other uses of this function). Fixes: ffc5089196446 ("[PATCH] Create kallsyms_lookup_size_offset()") Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kallsyms.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 95a260f9214b..136ce049c4ad 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -263,8 +263,10 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
{
char namebuf[KSYM_NAME_LEN];
- if (is_ksym_addr(addr))
- return !!get_symbol_pos(addr, symbolsize, offset);
+ if (is_ksym_addr(addr)) {
+ get_symbol_pos(addr, symbolsize, offset);
+ return 1;
+ }
return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
!!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
}