From: Alan Maguire alan.maguire@oracle.com
mainline inclusion from mainline-5.15-rc1 commit 8d44c3578b48d5f605eddcfd6a644e3944455a6b category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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If data is packed, data structures can store it outside of usual boundaries. For example a 4-byte int can be stored on a unaligned boundary in a case like this:
struct s { char f1; int f2; } __attribute((packed));
...the int is stored at an offset of one byte. Some platforms have problems dereferencing data that is not aligned with its size, and code exists to handle most cases of this for BTF typed data display. However pointer display was missed, and a simple function to test if "ptr_is_aligned(data, data_sz)" would help clarify this code.
Suggested-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alan Maguire alan.maguire@oracle.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/1626475617-25984-2-git-send-email-alan.maguire@o... (cherry picked from commit 8d44c3578b48d5f605eddcfd6a644e3944455a6b) Signed-off-by: Wang Yufen wangyufen@huawei.com --- tools/lib/bpf/btf_dump.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index ff21ac98ab07..8748d357d4ff 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -1659,6 +1659,11 @@ static int btf_dump_base_type_check_zero(struct btf_dump *d, return 0; }
+static bool ptr_is_aligned(const void *data, int data_sz) +{ + return ((uintptr_t)data) % data_sz == 0; +} + static int btf_dump_int_data(struct btf_dump *d, const struct btf_type *t, __u32 type_id, @@ -1677,7 +1682,7 @@ static int btf_dump_int_data(struct btf_dump *d, /* handle packed int data - accesses of integers not aligned on * int boundaries can cause problems on some platforms. */ - if (((uintptr_t)data) % sz) + if (!ptr_is_aligned(data, sz)) return btf_dump_bitfield_data(d, t, data, 0, 0);
switch (sz) { @@ -1744,7 +1749,7 @@ static int btf_dump_float_data(struct btf_dump *d, int sz = t->size;
/* handle unaligned data; copy to local union */ - if (((uintptr_t)data) % sz) { + if (!ptr_is_aligned(data, sz)) { memcpy(&fl, data, sz); flp = &fl; } @@ -1897,12 +1902,27 @@ static int btf_dump_struct_data(struct btf_dump *d, return err; }
+union ptr_data { + unsigned int p; + unsigned long long lp; +}; + static int btf_dump_ptr_data(struct btf_dump *d, const struct btf_type *t, __u32 id, const void *data) { - btf_dump_type_values(d, "%p", *(void **)data); + if (ptr_is_aligned(data, d->ptr_sz) && d->ptr_sz == sizeof(void *)) { + btf_dump_type_values(d, "%p", *(void **)data); + } else { + union ptr_data pt; + + memcpy(&pt, data, d->ptr_sz); + if (d->ptr_sz == 4) + btf_dump_type_values(d, "0x%x", pt.p); + else + btf_dump_type_values(d, "0x%llx", pt.lp); + } return 0; }
@@ -1915,7 +1935,7 @@ static int btf_dump_get_enum_value(struct btf_dump *d, int sz = t->size;
/* handle unaligned enum value */ - if (((uintptr_t)data) % sz) { + if (!ptr_is_aligned(data, sz)) { *value = (__s64)btf_dump_bitfield_get_data(d, t, data, 0, 0); return 0; }