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[bpf-next,v3,02/24] bpf: Allow specifying volatile type modifier for kptrs

Message ID 20221102202658.963008-3-memxor@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Local kptrs, BPF linked lists | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR fail PR summary
bpf/vmtest-bpf-next-VM_Test-1 pending Logs for ${{ matrix.test }} on ${{ matrix.arch }} with ${{ matrix.toolchain }}
bpf/vmtest-bpf-next-VM_Test-2 pending Logs for ShellCheck
bpf/vmtest-bpf-next-VM_Test-3 fail Logs for build for s390x with gcc
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bpf/vmtest-bpf-next-VM_Test-5 fail Logs for build for x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-6 success Logs for llvm-toolchain
bpf/vmtest-bpf-next-VM_Test-7 success Logs for set-matrix
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count fail Series longer than 15 patches (and no cover letter)
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1362 this patch: 1362
netdev/cc_maintainers warning 8 maintainers not CCed: sdf@google.com john.fastabend@gmail.com yhs@fb.com haoluo@google.com jolsa@kernel.org kpsingh@kernel.org song@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 159 this patch: 159
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1352 this patch: 1352
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 20 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Kumar Kartikeya Dwivedi Nov. 2, 2022, 8:26 p.m. UTC 
This is useful in particular to mark the pointer as volatile, so that
compiler treats each load and store to the field as a volatile access.
The alternative is having to define and use READ_ONCE and WRITE_ONCE in
the BPF program.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h | 5 +++++
 kernel/bpf/btf.c    | 3 +++
 2 files changed, 8 insertions(+)
diff mbox series

Patch

diff --git a/include/linux/btf.h b/include/linux/btf.h
index f9aababc5d78..86aad9b2ce02 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -288,6 +288,11 @@  static inline bool btf_type_is_typedef(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF;
 }
 
+static inline bool btf_type_is_volatile(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_VOLATILE;
+}
+
 static inline bool btf_type_is_func(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index eba603cec2c5..ad301e78f7ee 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3225,6 +3225,9 @@  static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	enum bpf_kptr_type type;
 	u32 res_id;
 
+	/* Permit modifiers on the pointer itself */
+	if (btf_type_is_volatile(t))
+		t = btf_type_by_id(btf, t->type);
 	/* For PTR, sz is always == 8 */
 	if (!btf_type_is_ptr(t))
 		return BTF_FIELD_IGNORE;