diff mbox series

[bpf-next,1/5] bpf: Add a flags value on trampoline frames.

Message ID 20220126214809.3868787-2-kuifeng@fb.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series Attach a cookie to a tracing program. | expand

Checks

Context Check Description
bpf/vmtest-bpf-next fail VM_Test
bpf/vmtest-bpf-next-PR fail PR summary
netdev/tree_selection success Clearly marked for bpf-next
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 success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 27 this patch: 27
netdev/cc_maintainers warning 16 maintainers not CCed: hpa@zytor.com rostedt@goodmis.org bp@alien8.de kpsingh@kernel.org yoshfuji@linux-ipv6.org john.fastabend@gmail.com kafai@fb.com songliubraving@fb.com x86@kernel.org dsahern@kernel.org dave.hansen@linux.intel.com yhs@fb.com mingo@redhat.com tglx@linutronix.de davem@davemloft.net netdev@vger.kernel.org
netdev/build_clang success Errors and warnings before: 18 this patch: 18
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 32 this patch: 32
netdev/checkpatch warning CHECK: No space is necessary after a cast WARNING: line length of 85 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Kui-Feng Lee Jan. 26, 2022, 9:48 p.m. UTC 
The flags indicate what values are below nargs.  It appears only if
one or more values are there.  The order in the flags, from LSB to
MSB, indicates the order of values in the trampoline frame.  LSB is at
the highest location, close to the flags and nargs.

Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>
---
 arch/x86/net/bpf_jit_comp.c | 17 ++++++++++++++++-
 kernel/bpf/verifier.c       |  2 +-
 kernel/trace/bpf_trace.c    | 23 ++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ce1f86f245c9..1c2d3ef57dad 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1976,7 +1976,7 @@  int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 				void *orig_call)
 {
 	int ret, i, nr_args = m->nr_args;
-	int regs_off, ip_off, args_off, stack_size = nr_args * 8;
+	int regs_off, flags_off, ip_off, args_off, stack_size = nr_args * 8;
 	struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY];
 	struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT];
 	struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN];
@@ -2019,6 +2019,11 @@  int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 	stack_size += 8;
 	args_off = stack_size;
 
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		stack_size += 8; /* room for flags */
+
+	flags_off = stack_size;
+
 	if (flags & BPF_TRAMP_F_IP_ARG)
 		stack_size += 8; /* room for IP address argument */
 
@@ -2044,6 +2049,16 @@  int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 	emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args);
 	emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -args_off);
 
+	if (flags & BPF_TRAMP_F_IP_ARG) {
+		/* Store flags
+		 * move rax, flags
+		 * mov QWORD PTR [rbp - flags_off], rax
+		 */
+		emit_mov_imm64(&prog, BPF_REG_0, 0,
+			       (u32) (flags & BPF_TRAMP_F_IP_ARG));
+		emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -flags_off);
+	}
+
 	if (flags & BPF_TRAMP_F_IP_ARG) {
 		/* Store IP address of the traced function:
 		 * mov rax, QWORD PTR [rbp + 8]
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8c5a46d41f28..ff91f5038010 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13585,7 +13585,7 @@  static int do_misc_fixups(struct bpf_verifier_env *env)
 		if (prog_type == BPF_PROG_TYPE_TRACING &&
 		    insn->imm == BPF_FUNC_get_func_ip) {
 			/* Load IP address from ctx - 16 */
-			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -16);
+			insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -24);
 
 			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1);
 			if (!new_prog)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 06a9e220069e..bf2c9d11ad05 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1009,10 +1009,31 @@  const struct bpf_func_proto bpf_snprintf_btf_proto = {
 	.arg5_type	= ARG_ANYTHING,
 };
 
+static int get_trampo_var_off(void *ctx, u32 flag)
+{
+	int off = 2;            /* All variables are placed before flags */
+	u32 flags = (u32)((u64 *)ctx)[-2];
+
+	if (!(flags & flag))
+		return -1;      /* The variable is not there */
+	if (flag & (flag - 1))
+		return -1;      /* 2 or more bits are set */
+
+	for (; flags & flag; flags &= flags - 1)
+		off++;
+
+	return off;
+}
+
 BPF_CALL_1(bpf_get_func_ip_tracing, void *, ctx)
 {
 	/* This helper call is inlined by verifier. */
-	return ((u64 *)ctx)[-2];
+	int off = get_trampo_var_off(ctx, BPF_TRAMP_F_IP_ARG);
+
+	if (off < 0)
+		return 0;
+
+	return ((u64 *)ctx)[-off];
 }
 
 static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = {