diff mbox series

[bpf-next,6/6] bpf, verifier: always mark destination of LDX as 64-bit

Message ID 20230912224654.6556-7-puranjay12@gmail.com (mailing list archive)
State Handled Elsewhere
Headers show
Series bpf: verifier: stop emitting zext for LDX | expand

Checks

Context Check Description
conchuod/cover_letter success Series has a cover letter
conchuod/tree_selection success Guessed tree name to be for-next at HEAD 0bb80ecc33a8
conchuod/fixes_present success Fixes tag not required for -next series
conchuod/maintainers_pattern success MAINTAINERS pattern errors before the patch: 5 and now 5
conchuod/verify_signedoff success Signed-off-by tag matches author and committer
conchuod/kdoc success Errors and warnings before: 0 this patch: 0
conchuod/build_rv64_clang_allmodconfig success Errors and warnings before: 9 this patch: 9
conchuod/module_param success Was 0 now: 0
conchuod/build_rv64_gcc_allmodconfig success Errors and warnings before: 9 this patch: 9
conchuod/build_rv32_defconfig success Build OK
conchuod/dtb_warn_rv64 success Errors and warnings before: 25 this patch: 25
conchuod/header_inline success No static functions without inline keyword in header files
conchuod/checkpatch success total: 0 errors, 0 warnings, 0 checks, 10 lines checked
conchuod/build_rv64_nommu_k210_defconfig success Build OK
conchuod/verify_fixes success No Fixes tag
conchuod/build_rv64_nommu_virt_defconfig success Build OK

Commit Message

Puranjay Mohan Sept. 12, 2023, 10:46 p.m. UTC 
All 64-bit JITs utilize a single instruction to load + zero-extend a
byte, word, or a half-word. The optimisation of emitting zext for LDX is
not useful for most of the JITs.

All the JITs that relied on the verifier for zero extension of LDX
desitination registers have been modified to always zero extend the
destination.

Now the verifier can safely mark LDX destination as 64-bit and stop
emitting zero-extension instructions for it.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
---
 kernel/bpf/verifier.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index dbba2b806017..02a1ac1a1327 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3028,9 +3028,7 @@  static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		return false;
 
 	if (class == BPF_LDX) {
-		if (t != SRC_OP)
-			return BPF_SIZE(code) == BPF_DW;
-		/* LDX source must be ptr. */
+		/* LDX source must be a ptr. and LDX destination is always zero-extended. */
 		return true;
 	}