Messages in this thread Patch in this message | | | Date | Tue, 26 Nov 2013 18:44:46 +0100 | From | Oleg Nesterov <> | Subject | [RFC PATCH 2/2] tracing: Teach FETCH_MTD_symbol to handle per-cpu data |
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FETCH_FUNC_NAME(symbol) blindly dereferences sc->addr + sc->offset, this is not what we want if this symbol is per-cpu. Change this code to use this_cpu_ptr(sc->addr) in this case.
Note: this doesn't work for modules, but module's per-cpu data is not visible for kallsyms_lookup_name() anyway.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/trace/trace_probe.c | 22 ++++++++++++++++++---- 1 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 097cc80..a0144b6 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -252,14 +252,28 @@ static struct symbol_cache *alloc_symbol_cache(const char *sym, long offset) return sc; } +static void *sc_calc_addr(struct symbol_cache *sc) +{ + void *addr = (void*)sc->addr; + + if (addr) { + if (addr >= (void *)__per_cpu_start && + addr < (void *)__per_cpu_end) + addr = this_cpu_ptr(addr); + + addr += sc->offset; + } + + return addr; +} + #define DEFINE_FETCH_symbol(type) \ static __kprobes void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs,\ void *data, void *dest) \ { \ - struct symbol_cache *sc = data; \ - long off = sc->offset; \ - if (sc->addr) \ - fetch_memory_##type(regs, (void *)sc->addr + off, dest);\ + void *addr = sc_calc_addr(data); \ + if (addr) \ + fetch_memory_##type(regs, addr, dest); \ else \ *(type *)dest = 0; \ } -- 1.5.5.1
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