From a68eb730558fb90bc8d9524564d8f9e58f3ccac1 Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Mon, 7 Oct 2019 11:20:55 +0200
Subject: Improve ABI backward & forward compatibillity
- Padd the compressor config union
- 128 bytes aught to be enough for everyone, i.e. future compressors.
- Insist that the padding space is initialized to 0. If a field gets
added to an existing compressor, it can test for 0 as a sentinel
value.
- Add a size field to the hook structure, aka "the Microsoft way".
- The explanation is in the comment.
- Don't make the Microsoft mistake of checking for >=, insist on *exact*
size match. Future users will need a fallback if their hooks are
rejected. But at least they will be rejected instead of silently not
being used.
- Add an unsupported flag check to the dir tree reader.
- Add a basic abi unit test that, for now, checks the size of the compressor
config struct fields.
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
lib/sqfs/comp/compressor.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
(limited to 'lib/sqfs/comp')
diff --git a/lib/sqfs/comp/compressor.c b/lib/sqfs/comp/compressor.c
index bfc20b7..902ce92 100644
--- a/lib/sqfs/comp/compressor.c
+++ b/lib/sqfs/comp/compressor.c
@@ -87,12 +87,42 @@ bool sqfs_compressor_exists(E_SQFS_COMPRESSOR id)
sqfs_compressor_t *sqfs_compressor_create(const sqfs_compressor_config_t *cfg)
{
+ sqfs_u8 padd0[sizeof(cfg->opt)];
+ int ret;
+
if (cfg == NULL || cfg->id < SQFS_COMP_MIN || cfg->id > SQFS_COMP_MAX)
return NULL;
if (compressors[cfg->id] == NULL)
return NULL;
+ memset(padd0, 0, sizeof(padd0));
+
+ switch (cfg->id) {
+ case SQFS_COMP_XZ:
+ ret = memcmp(cfg->opt.xz.padd0, padd0,
+ sizeof(cfg->opt.xz.padd0));
+ break;
+ case SQFS_COMP_LZO:
+ ret = memcmp(cfg->opt.lzo.padd0, padd0,
+ sizeof(cfg->opt.lzo.padd0));
+ break;
+ case SQFS_COMP_ZSTD:
+ ret = memcmp(cfg->opt.zstd.padd0, padd0,
+ sizeof(cfg->opt.zstd.padd0));
+ break;
+ case SQFS_COMP_GZIP:
+ ret = memcmp(cfg->opt.gzip.padd0, padd0,
+ sizeof(cfg->opt.gzip.padd0));
+ break;
+ default:
+ ret = memcmp(cfg->opt.padd0, padd0, sizeof(cfg->opt.padd0));
+ break;
+ }
+
+ if (ret != 0)
+ return NULL;
+
return compressors[cfg->id](cfg);
}
--
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