diff options
Diffstat (limited to 'exec.c')
| -rw-r--r-- | exec.c | 79 |
1 files changed, 65 insertions, 14 deletions
@@ -59,8 +59,6 @@ static void bfs_exec_debug(const struct bfs_exec *execbuf, const char *format, . va_end(args); } -extern char **environ; - /** Determine the size of a single argument, for comparison to arg_max. */ static size_t bfs_exec_arg_size(const char *arg) { return sizeof(arg) + strlen(arg) + 1; @@ -79,6 +77,7 @@ static size_t bfs_exec_arg_max(const struct bfs_exec *execbuf) { } // We have to share space with the environment variables + extern char **environ; for (char **envp = environ; *envp; ++envp) { arg_max -= bfs_exec_arg_size(*envp); } @@ -131,6 +130,7 @@ struct bfs_exec *bfs_exec_parse(const struct bfs_ctx *ctx, char **argv, enum bfs execbuf->argv_cap = 0; execbuf->arg_size = 0; execbuf->arg_max = 0; + execbuf->arg_min = 0; execbuf->wd_fd = -1; execbuf->wd_path = NULL; execbuf->wd_len = 0; @@ -183,6 +183,7 @@ struct bfs_exec *bfs_exec_parse(const struct bfs_ctx *ctx, char **argv, enum bfs execbuf->argc = execbuf->tmpl_argc - 1; execbuf->arg_max = bfs_exec_arg_max(execbuf); + execbuf->arg_min = execbuf->arg_max; } return execbuf; @@ -461,6 +462,54 @@ static bool bfs_exec_args_remain(const struct bfs_exec *execbuf) { return execbuf->argc >= execbuf->tmpl_argc; } +/** Compute the current ARG_MAX estimate for binary search. */ +static size_t bfs_exec_estimate_max(const struct bfs_exec *execbuf) { + size_t min = execbuf->arg_min; + size_t max = execbuf->arg_max; + return min + (max - min)/2; +} + +/** Update the ARG_MAX lower bound from a successful execution. */ +static void bfs_exec_update_min(struct bfs_exec *execbuf) { + if (execbuf->arg_size > execbuf->arg_min) { + execbuf->arg_min = execbuf->arg_size; + + // Don't let min exceed max + if (execbuf->arg_min > execbuf->arg_max) { + execbuf->arg_min = execbuf->arg_max; + } + + size_t estimate = bfs_exec_estimate_max(execbuf); + bfs_exec_debug(execbuf, "ARG_MAX between [%zu, %zu], trying %zu\n", + execbuf->arg_min, execbuf->arg_max, estimate); + } +} + +/** Update the ARG_MAX upper bound from a failed execution. */ +static size_t bfs_exec_update_max(struct bfs_exec *execbuf) { + bfs_exec_debug(execbuf, "Got E2BIG, shrinking argument list...\n"); + + if (execbuf->arg_size < execbuf->arg_max) { + execbuf->arg_max = execbuf->arg_size; + + // Don't let min exceed max + if (execbuf->arg_min > execbuf->arg_max) { + execbuf->arg_min = execbuf->arg_max; + } + } + + if (execbuf->arg_size <= execbuf->arg_min) { + // Lower bound was wrong, restart binary search. + execbuf->arg_min = 0; + } + + // Binary search for a more precise bound + size_t estimate = bfs_exec_estimate_max(execbuf); + bfs_exec_debug(execbuf, "ARG_MAX between [%zu, %zu], trying %zu\n", + execbuf->arg_min, execbuf->arg_max, estimate); + return estimate; +} + /** Execute the pending command from a BFS_EXEC_MULTI execbuf. */ static int bfs_exec_flush(struct bfs_exec *execbuf) { int ret = 0, error = 0; @@ -470,20 +519,24 @@ static int bfs_exec_flush(struct bfs_exec *execbuf) { execbuf->argv[execbuf->argc] = NULL; ret = bfs_exec_spawn(execbuf); error = errno; - if (ret == 0 || error != E2BIG) { + if (ret == 0) { + bfs_exec_update_min(execbuf); + break; + } else if (error != E2BIG) { break; } // Try to recover from E2BIG by trying fewer and fewer arguments // until they fit - bfs_exec_debug(execbuf, "Got E2BIG, shrinking argument list...\n"); - execbuf->argv[execbuf->argc] = execbuf->argv[execbuf->argc - 1]; - execbuf->arg_size -= bfs_exec_arg_size(execbuf->argv[execbuf->argc]); - --execbuf->argc; + size_t new_max = bfs_exec_update_max(execbuf); + while (execbuf->arg_size > new_max) { + execbuf->argv[execbuf->argc] = execbuf->argv[execbuf->argc - 1]; + execbuf->arg_size -= bfs_exec_arg_size(execbuf->argv[execbuf->argc]); + --execbuf->argc; + } } - size_t new_argc = execbuf->argc; - size_t new_size = execbuf->arg_size; + size_t new_argc = execbuf->argc; for (size_t i = execbuf->tmpl_argc - 1; i < new_argc; ++i) { free(execbuf->argv[i]); } @@ -491,9 +544,6 @@ static int bfs_exec_flush(struct bfs_exec *execbuf) { execbuf->arg_size = 0; if (new_argc < orig_argc) { - execbuf->arg_max = new_size; - bfs_exec_debug(execbuf, "ARG_MAX: %zu\n", execbuf->arg_max); - // If we recovered from E2BIG, there are unused arguments at the // end of the list for (size_t i = new_argc + 1; i <= orig_argc; ++i) { @@ -526,10 +576,11 @@ static bool bfs_exec_changed_dirs(const struct bfs_exec *execbuf, const struct B /** Check if we need to flush the execbuf because we're too big. */ static bool bfs_exec_would_overflow(const struct bfs_exec *execbuf, const char *arg) { + size_t arg_max = bfs_exec_estimate_max(execbuf); size_t next_size = execbuf->arg_size + bfs_exec_arg_size(arg); - if (next_size > execbuf->arg_max) { + if (next_size > arg_max) { bfs_exec_debug(execbuf, "Command size (%zu) would exceed maximum (%zu), executing buffered command\n", - next_size, execbuf->arg_max); + next_size, arg_max); return true; } |