perf llvm: Fix inadvertent file creation

The LLVM template is first echo-ed into command_out and then
command_out executed. The echo surrounds the template with double
quotes, however, the template itself may contain quotes. This is
generally innocuous but in tools/perf/tests/bpf-script-test-prologue.c
we see:
...
SEC("func=null_lseek file->f_mode offset orig")
...
where the first double quote ends the double quote of the echo, then
the > redirects output into a file called f_mode.

To avoid this inadvertent behavior substitute redirects and similar
characters to be ASCII control codes, then substitute the output in
the echo back again.

Fixes: 5eab5a7ee032acaa ("perf llvm: Display eBPF compiling command in debug output")
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: llvm@lists.linux.dev
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230105082609.344538-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 650ffe3..4e8e243 100644 (file)
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -531,14 +531,37 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
 
        pr_debug("llvm compiling command template: %s\n", template);
 
+       /*
+        * Below, substitute control characters for values that can cause the
+        * echo to misbehave, then substitute the values back.
+        */
        err = -ENOMEM;
-       if (asprintf(&command_echo, "echo -n \"%s\"", template) < 0)
+       if (asprintf(&command_echo, "echo -n \a%s\a", template) < 0)
                goto errout;
 
+#define SWAP_CHAR(a, b) do { if (*p == a) *p = b; } while (0)
+       for (char *p = command_echo; *p; p++) {
+               SWAP_CHAR('<', '\001');
+               SWAP_CHAR('>', '\002');
+               SWAP_CHAR('"', '\003');
+               SWAP_CHAR('\'', '\004');
+               SWAP_CHAR('|', '\005');
+               SWAP_CHAR('&', '\006');
+               SWAP_CHAR('\a', '"');
+       }
        err = read_from_pipe(command_echo, (void **) &command_out, NULL);
        if (err)
                goto errout;
 
+       for (char *p = command_out; *p; p++) {
+               SWAP_CHAR('\001', '<');
+               SWAP_CHAR('\002', '>');
+               SWAP_CHAR('\003', '"');
+               SWAP_CHAR('\004', '\'');
+               SWAP_CHAR('\005', '|');
+               SWAP_CHAR('\006', '&');
+       }
+#undef SWAP_CHAR
        pr_debug("llvm compiling command : %s\n", command_out);
 
        err = read_from_pipe(template, &obj_buf, &obj_buf_sz);