Re: [PATCH-V2] perf/probe: verify instruction/offset in perf before adding a uprobe

Arnaldo Carvalho de Melo
2012-04-24T11:23:49Z

Em Tue, Apr 24, 2012 at 12:06:46PM +0530, Prashanth Nageshappa escreveu:
> This patch is to augment Srikar's perf support for uprobes patch
> (https://lkml.org/lkml/2012/4/11/191) with the following features:
>
> a. Instruction verification for user space tracing
> b. Function boundary validation support to uprobes as its kernel
> counterpart (Commit-ID: 1c1bc922).
>
> This will help in ensuring uprobe is placed at right location inside
> the intended function.
>
> To verify instructions in perf before adding a uprobe, we need to use
> arch/x86/lib/insn.c. Since perf Makefile enables -Wswitch-default flag
> it causes build warnings/failures. Masami's patch
> https://lkml.org/lkml/2012/4/12/598 addresses those warnings and it is
> a pre-req for this patch.
>
> v2 addresses Masami's review comments: Rebuild insn.c and inat.c while
> building perf and a few other minor ones.

Some minor nits below

> --- /dev/null
> +++ b/tools/perf/arch/x86/util/probe-event.c
> @@ -0,0 +1,84 @@
> +bool can_probe(char *name, unsigned long long vaddr, unsigned long offset,
> + u8 class)
> +{
> + unsigned long long eaddr, saddr;

Why not the much shorter 'u64'?

> + unsigned long fileoffset, readbytes;
> + int fd = 0;
> + bool ret = false;
> + char *buf = NULL;
> + struct insn insn;
> +
> + fd = open(name, O_RDONLY);
> + if (fd == -1) {
> + pr_warning("Failed to open %s: %s\n", name, strerror(errno));
> + return ret;
> + }
> + buf = (char *)malloc(offset + MAX_INSN_SIZE);

No need to cast malloc's return

> + if (buf == NULL) {
> + pr_warning("Failed to allocate memory");
> + goto out;
> + }
> + fileoffset = lseek(fd, vaddr, SEEK_SET);
> + if (fileoffset != vaddr) {
> + pr_warning("Failed to lseek %s: %s\n", name, strerror(errno));
> + goto out;

Goto out_close and...

> + }
> + saddr = (unsigned long long)buf;
> + eaddr = (unsigned long long)buf + offset;
> + readbytes = read(fd, buf, offset + MAX_INSN_SIZE);
> + if (readbytes != offset + MAX_INSN_SIZE) {
> + pr_warning("Failed to read %s: %s\n", name, strerror(errno));
> + goto out;

out_close

> + }
> + while (saddr < eaddr) {
> + insn_init(&insn, (void *)saddr, class == ELFCLASS64);
> + insn_get_length(&insn);
> + saddr += insn.length;
> + }
> + ret = (saddr == eaddr);
> +
> +out:
> + if (buf)
> + free(buf);

free can handle NULL pointers just fine

> +
> + if (fd)
> + close(fd);

You can move this to before 'free' and label it out_close,
avoiding the test.

> +
> + return ret;
> +}
> diff --git a/tools/perf/util/include/linux/string.h b/tools/perf/util/include/linux/string.h
> index 3b2f590..9d5eb21 100644
> --- a/tools/perf/util/include/linux/string.h
> +++ b/tools/perf/util/include/linux/string.h
> @@ -1 +1,2 @@
> #include <string.h>
> +#include <perf.h>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index b7dec82..8f3de61 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2254,6 +2254,17 @@ int show_available_funcs(const char *target, struct strfilter *_filter,
> }
>
> /*
> + * Check if a given offset from start of a function is valid or not
> + */
> +bool __attribute__((weak)) can_probe(char *name __used,
> + unsigned long long vaddr __used,
> + unsigned long offset __used,
> + u8 class __used)
> +{
> + return true;
> +}
> +
> +/*
> * uprobe_events only accepts address:
> * Convert function and any offset to address
> */
> @@ -2307,7 +2318,16 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>
> if (map->start > sym->start)
> vaddr = map->start;
> - vaddr += sym->start + pp->offset + map->pgoff;
> +
> + vaddr += sym->start + map->pgoff;
> + if (pp->offset)
> + if ((vaddr + pp->offset > sym->end) ||
> + !can_probe(name, vaddr, pp->offset,
> + map->dso->class)) {
> + pr_err("Failed to insert probe, ensure offset is within function and on insn boundary.\n");
> + return -EINVAL;
> + }

Multi line if bodies gets visually nicer when enclosed with {}

> + vaddr += pp->offset;
> pp->offset = 0;
>
> if (!pev->event) {
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index f9f3de8..af96594 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -137,4 +137,6 @@ extern int show_available_funcs(const char *module, struct strfilter *filter,
> /* Maximum index number of event-name postfix */
> #define MAX_EVENT_INDEX 1024
>
> +extern bool can_probe(char *name, unsigned long long vaddr,
> + unsigned long offset, u8 class);
> #endif /*_PROBE_EVENT_H */
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index caaf75a..be58b06 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1184,6 +1184,7 @@ static int dso__load_sym(struct dso *dso, struct map *map, const char *name,
> goto out_close;
> }
>
> + dso->class = gelf_getclass(elf);
> if (gelf_getehdr(elf, &ehdr) == NULL) {
> pr_debug("%s: cannot get elf header.\n", __func__);
> goto out_elf_end;
> @@ -1326,6 +1327,7 @@ static int dso__load_sym(struct dso *dso, struct map *map, const char *name,
> curr_dso->kernel = dso->kernel;
> curr_dso->long_name = dso->long_name;
> curr_dso->long_name_len = dso->long_name_len;
> + curr_dso->class = dso->class;
> curr_map = map__new2(start, curr_dso,
> map->type);
> if (curr_map == NULL) {
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 9e7742c..1d0cc28 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -174,6 +174,7 @@ struct dso {
> char *long_name;
> u16 long_name_len;
> u16 short_name_len;
> + u8 class;
> char name[0];
> };
>