From 412a200ae4ebd980fc5be0ae449f110bae65504b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C5=8Dshin?= <git@wholezero.org>
Date: Fri, 5 Jan 2024 15:35:01 -0500
Subject: [PATCH] Support binfmt_misc P flag in APE loader (#1058)
This allows ape to automatically preserve `argv[0]` [as of Linux kernel
5.12][0] if the [binfmt_misc][1] registration contains the P flag.
This also removes may_path_search, which was identical to the literally
flag in usage. As a result, FindCommand is subsumed into Commandv.
[0]: https://patchew.org/QEMU/20210222105004.1642234-1-laurent@vivier.eu/
[1]: https://www.kernel.org/doc/html/latest/admin-guide/binfmt-misc.html
---
ape/loader.c | 124 ++++++++++++++++++++++-----------------------------
1 file changed, 54 insertions(+), 70 deletions(-)
diff --git a/ape/loader.c b/ape/loader.c
index ca582bd4a..129246764 100644
--- a/ape/loader.c
+++ b/ape/loader.c
@@ -113,41 +113,44 @@
#define EXTERN_C
#endif
-#define O_RDONLY 0
-#define PROT_NONE 0
-#define PROT_READ 1
-#define PROT_WRITE 2
-#define PROT_EXEC 4
-#define MAP_SHARED 1
-#define MAP_PRIVATE 2
-#define MAP_FIXED 16
-#define MAP_ANONYMOUS (IsLinux() ? 32 : 4096)
-#define MAP_NORESERVE (IsLinux() ? 16384 : 0)
-#define ELFCLASS32 1
-#define ELFDATA2LSB 1
-#define EM_NEXGEN32E 62
-#define EM_AARCH64 183
-#define ET_EXEC 2
-#define ET_DYN 3
-#define PT_LOAD 1
-#define PT_DYNAMIC 2
-#define PT_INTERP 3
-#define EI_CLASS 4
-#define EI_DATA 5
-#define PF_X 1
-#define PF_W 2
-#define PF_R 4
-#define AT_PHDR 3
-#define AT_PHENT 4
-#define AT_PHNUM 5
-#define AT_PAGESZ 6
-#define AT_EXECFN_LINUX 31
-#define AT_EXECFN_NETBSD 2014
-#define X_OK 1
-#define XCR0_SSE 2
-#define XCR0_AVX 4
-#define PR_SET_MM 35
-#define PR_SET_MM_EXE_FILE 13
+#define O_RDONLY 0
+#define PROT_NONE 0
+#define PROT_READ 1
+#define PROT_WRITE 2
+#define PROT_EXEC 4
+#define MAP_SHARED 1
+#define MAP_PRIVATE 2
+#define MAP_FIXED 16
+#define MAP_ANONYMOUS (IsLinux() ? 32 : 4096)
+#define MAP_NORESERVE (IsLinux() ? 16384 : 0)
+#define ELFCLASS32 1
+#define ELFDATA2LSB 1
+#define EM_NEXGEN32E 62
+#define EM_AARCH64 183
+#define ET_EXEC 2
+#define ET_DYN 3
+#define PT_LOAD 1
+#define PT_DYNAMIC 2
+#define PT_INTERP 3
+#define EI_CLASS 4
+#define EI_DATA 5
+#define PF_X 1
+#define PF_W 2
+#define PF_R 4
+#define AT_PHDR 3
+#define AT_PHENT 4
+#define AT_PHNUM 5
+#define AT_PAGESZ 6
+#define AT_FLAGS 8
+#define AT_FLAGS_PRESERVE_ARGV0_BIT 0
+#define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT)
+#define AT_EXECFN_LINUX 31
+#define AT_EXECFN_NETBSD 2014
+#define X_OK 1
+#define XCR0_SSE 2
+#define XCR0_AVX 4
+#define PR_SET_MM 35
+#define PR_SET_MM_EXE_FILE 13
#define READ32(S) \
((unsigned)(255 & (S)[3]) << 030 | (unsigned)(255 & (S)[2]) << 020 | \
@@ -572,39 +575,15 @@ static char SearchPath(struct PathSearcher *ps) {
}
}
-static char FindCommand(struct PathSearcher *ps) {
- ps->path[0] = 0;
-
- /* paths are always 100% taken literally when a slash exists
- $ ape foo/bar.com arg1 arg2 */
- if (MemChr(ps->name, '/', ps->namelen)) {
- return AccessCommand(ps, 0);
- }
-
- /* we don't run files in the current directory
- $ ape foo.com arg1 arg2
- unless $PATH has an empty string entry, e.g.
- $ expert PATH=":/bin"
- $ ape foo.com arg1 arg2
- however we will execute this
- $ ape - foo.com foo.com arg1 arg2
- because cosmo's execve needs it */
- if (ps->literally && AccessCommand(ps, 0)) {
- return 1;
- }
-
- /* otherwise search for name on $PATH */
- return SearchPath(ps);
-}
-
static char *Commandv(struct PathSearcher *ps, int os, char *name,
- const char *syspath, int may_path_search) {
- if (!may_path_search) return name;
+ const char *syspath) {
+ if (!(ps->namelen = StrLen((ps->name = name)))) return 0;
+ if (ps->literally || MemChr(ps->name, '/', ps->namelen)) return name;
ps->os = os;
ps->syspath = syspath ? syspath : "/bin:/usr/local/bin:/usr/bin";
- if (!(ps->namelen = StrLen((ps->name = name)))) return 0;
if (ps->namelen + 1 > sizeof(ps->path)) return 0;
- if (FindCommand(ps)) {
+ ps->path[0] = 0;
+ if (SearchPath(ps)) {
return ps->path;
} else {
return 0;
@@ -913,10 +892,10 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
char dl) {
int rc, n;
unsigned i;
- char literally;
const char *ape;
int c, fd, os, argc;
struct ApeLoader *M;
+ char arg0, literally;
unsigned long pagesz;
union ElfEhdrBuf *ebuf;
long *auxv, *ap, *endp, *sp2;
@@ -961,11 +940,14 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
/* detect netbsd and find end of words */
pagesz = 0;
+ arg0 = 0;
for (ap = auxv; ap[0]; ap += 2) {
if (ap[0] == AT_PAGESZ) {
pagesz = ap[1];
} else if (SupportsNetbsd() && !os && ap[0] == AT_EXECFN_NETBSD) {
os = NETBSD;
+ } else if (SupportsLinux() && ap[0] == AT_FLAGS) {
+ arg0 = !!(ap[1] & AT_FLAGS_PRESERVE_ARGV0);
}
}
if (!pagesz) {
@@ -979,8 +961,12 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
}
/* we can load via shell, shebang, or binfmt_misc */
- int may_path_search = 1;
- if ((literally = argc >= 3 && !StrCmp(argv[1], "-"))) {
+ if (arg0) {
+ literally = 1;
+ prog = (char *)sp[2];
+ argc = sp[2] = sp[0] - 2;
+ argv = (char **)((sp += 2) + 1);
+ } else if ((literally = argc >= 3 && !StrCmp(argv[1], "-"))) {
/* if the first argument is a hyphen then we give the user the
power to change argv[0] or omit it entirely. most operating
systems don't permit the omission of argv[0] but we do, b/c
@@ -988,7 +974,6 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
prog = (char *)sp[3];
argc = sp[3] = sp[0] - 3;
argv = (char **)((sp += 3) + 1);
- may_path_search = 0;
} else if (argc < 2) {
ShowUsage(os, 2, 1);
} else {
@@ -1029,8 +1014,7 @@ EXTERN_C __attribute__((__noreturn__)) void ApeLoader(long di, long *sp,
}
/* resolve path of executable and read its first page */
- if (!(exe = Commandv(&M->ps, os, prog, GetEnv(envp, "PATH"),
- may_path_search))) {
+ if (!(exe = Commandv(&M->ps, os, prog, GetEnv(envp, "PATH")))) {
Pexit(os, prog, 0, "not found (maybe chmod +x or ./ needed)");
} else if ((fd = Open(exe, O_RDONLY, 0, os)) < 0) {
Pexit(os, exe, fd, "open");