Messages in this thread Patch in this message | | | Date | Sat, 23 Nov 2013 21:16:05 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] tracing: Introduce "pseudo registers" for FETCH_MTD_reg |
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The probe can dump the registers or memory, but it is not possible to dump, say, current->pid. This patch adds the pseudo regs table, currently it has only two methods to get current/smp_processor_id but it can be trivially extended.
This syntax is %%pseudo-reg-name, I agree in advance with any other naming.
Test-case: 452 == offsetof(task_struct, pid), 39 == __NR_getpid,
# perf probe 'sys_getpid%return ret=$retval:s32 pid=+452(%%current):s32' # perf record -e probe:sys_getpid perl -e 'syscall 39' # perf --no-pager script | tail -1 perl 586 [001] 753.102549: probe:sys_getpid: \ (ffffffff81052c00 <- ffffffff8134d012) ret=586 pid=586
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/trace/trace_probe.c | 57 +++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 54 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 412e959..e167c0a 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -109,13 +109,14 @@ DEFINE_FETCH_##method(u64) (FETCH_FUNC_NAME(method, string_size) == fn)) \ && (fn != NULL)) +static unsigned long probe_get_register(struct pt_regs *, unsigned long); + /* Data fetch function templates */ #define DEFINE_FETCH_reg(type) \ static __kprobes void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, \ void *offset, void *dest) \ { \ - *(type *)dest = (type)regs_get_register(regs, \ - (unsigned int)((unsigned long)offset)); \ + *(type *)dest = (type)probe_get_register(regs, (long)offset); \ } DEFINE_BASIC_FETCH_FUNCS(reg) /* No string on the register */ @@ -548,6 +549,52 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, return ret; } +#define PSEUDO_REG_OFFSET 4096 /* arbitrary value > MAX_REG_OFFSET */ + +static unsigned long pseudo_reg_cpu(void) +{ + return (unsigned long)raw_smp_processor_id(); +} + +static unsigned long pseudo_reg_current(void) +{ + return (unsigned long)current; +} + +static struct { + const char *name; + unsigned long (*fetch)(void); +} +const pseudo_reg_table[] = { + { + .name = "cpu", + .fetch = pseudo_reg_cpu, + }, + { + .name = "current", + .fetch = pseudo_reg_current, + }, +}; + +static unsigned long probe_get_register(struct pt_regs *regs, unsigned long offset) +{ + if (offset < PSEUDO_REG_OFFSET) + return regs_get_register(regs, offset); + + return pseudo_reg_table[offset - PSEUDO_REG_OFFSET].fetch(); +} + +static int pseudo_reg_query_offset(const char *name) +{ + int nr; + + for (nr = 0; nr < ARRAY_SIZE(pseudo_reg_table); ++nr) + if (strcmp(pseudo_reg_table[nr].name, name) == 0) + return PSEUDO_REG_OFFSET + nr; + + return -EINVAL; +} + /* Recursive argument parser */ static int parse_probe_arg(char *arg, const struct fetch_type *t, struct fetch_param *f, bool is_return, bool is_kprobe) @@ -569,7 +616,11 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t, break; case '%': /* named register */ - ret = regs_query_register_offset(arg + 1); + if (arg[1] == '%') + ret = pseudo_reg_query_offset(arg + 2); + else + ret = regs_query_register_offset(arg + 1); + if (ret >= 0) { f->fn = t->fetch[FETCH_MTD_reg]; f->data = (void *)(unsigned long)ret; -- 1.5.5.1
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