[PATCH v1] perf bpf-prologue: Remove unused file

[PATCH v1] perf bpf-prologue: Remove unused file

[Ian Rogers]

Commit 3d6dfae88917 ("perf parse-events: Remove BPF event support")
removed building bpf-prologue.c but failed to remove the actual file.

Fixes: 3d6dfae88917 ("perf parse-events: Remove BPF event support")
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/bpf-prologue.c | 508 ---------------------------------
 1 file changed, 508 deletions(-)
 delete mode 100644 tools/perf/util/bpf-prologue.c

diff --git a/tools/perf/util/bpf-prologue.c b/tools/perf/util/bpf-prologue.c
deleted file mode 100644
index 9887ae09242d..000000000000
--- a/tools/perf/util/bpf-prologue.c
+++ /dev/null
@@ -1,508 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * bpf-prologue.c
- *
- * Copyright (C) 2015 He Kuang <hekuang@huawei.com>
- * Copyright (C) 2015 Wang Nan <wangnan0@huawei.com>
- * Copyright (C) 2015 Huawei Inc.
- */
-
-#include <bpf/libbpf.h>
-#include "debug.h"
-#include "bpf-loader.h"
-#include "bpf-prologue.h"
-#include "probe-finder.h"
-#include <errno.h>
-#include <stdlib.h>
-#include <dwarf-regs.h>
-#include <linux/filter.h>
-
-#define BPF_REG_SIZE		8
-
-#define JMP_TO_ERROR_CODE	-1
-#define JMP_TO_SUCCESS_CODE	-2
-#define JMP_TO_USER_CODE	-3
-
-struct bpf_insn_pos {
-	struct bpf_insn *begin;
-	struct bpf_insn *end;
-	struct bpf_insn *pos;
-};
-
-static inline int
-pos_get_cnt(struct bpf_insn_pos *pos)
-{
-	return pos->pos - pos->begin;
-}
-
-static int
-append_insn(struct bpf_insn new_insn, struct bpf_insn_pos *pos)
-{
-	if (!pos->pos)
-		return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
-
-	if (pos->pos + 1 >= pos->end) {
-		pr_err("bpf prologue: prologue too long\n");
-		pos->pos = NULL;
-		return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
-	}
-
-	*(pos->pos)++ = new_insn;
-	return 0;
-}
-
-static int
-check_pos(struct bpf_insn_pos *pos)
-{
-	if (!pos->pos || pos->pos >= pos->end)
-		return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
-	return 0;
-}
-
-/*
- * Convert type string (u8/u16/u32/u64/s8/s16/s32/s64 ..., see
- * Documentation/trace/kprobetrace.rst) to size field of BPF_LDX_MEM
- * instruction (BPF_{B,H,W,DW}).
- */
-static int
-argtype_to_ldx_size(const char *type)
-{
-	int arg_size = type ? atoi(&type[1]) : 64;
-
-	switch (arg_size) {
-	case 8:
-		return BPF_B;
-	case 16:
-		return BPF_H;
-	case 32:
-		return BPF_W;
-	case 64:
-	default:
-		return BPF_DW;
-	}
-}
-
-static const char *
-insn_sz_to_str(int insn_sz)
-{
-	switch (insn_sz) {
-	case BPF_B:
-		return "BPF_B";
-	case BPF_H:
-		return "BPF_H";
-	case BPF_W:
-		return "BPF_W";
-	case BPF_DW:
-		return "BPF_DW";
-	default:
-		return "UNKNOWN";
-	}
-}
-
-/* Give it a shorter name */
-#define ins(i, p) append_insn((i), (p))
-
-/*
- * Give a register name (in 'reg'), generate instruction to
- * load register into an eBPF register rd:
- *   'ldd target_reg, offset(ctx_reg)', where:
- * ctx_reg is pre initialized to pointer of 'struct pt_regs'.
- */
-static int
-gen_ldx_reg_from_ctx(struct bpf_insn_pos *pos, int ctx_reg,
-		     const char *reg, int target_reg)
-{
-	int offset = regs_query_register_offset(reg);
-
-	if (offset < 0) {
-		pr_err("bpf: prologue: failed to get register %s\n",
-		       reg);
-		return offset;
-	}
-	ins(BPF_LDX_MEM(BPF_DW, target_reg, ctx_reg, offset), pos);
-
-	return check_pos(pos);
-}
-
-/*
- * Generate a BPF_FUNC_probe_read function call.
- *
- * src_base_addr_reg is a register holding base address,
- * dst_addr_reg is a register holding dest address (on stack),
- * result is:
- *
- *  *[dst_addr_reg] = *([src_base_addr_reg] + offset)
- *
- * Arguments of BPF_FUNC_probe_read:
- *     ARG1: ptr to stack (dest)
- *     ARG2: size (8)
- *     ARG3: unsafe ptr (src)
- */
-static int
-gen_read_mem(struct bpf_insn_pos *pos,
-	     int src_base_addr_reg,
-	     int dst_addr_reg,
-	     long offset,
-	     int probeid)
-{
-	/* mov arg3, src_base_addr_reg */
-	if (src_base_addr_reg != BPF_REG_ARG3)
-		ins(BPF_MOV64_REG(BPF_REG_ARG3, src_base_addr_reg), pos);
-	/* add arg3, #offset */
-	if (offset)
-		ins(BPF_ALU64_IMM(BPF_ADD, BPF_REG_ARG3, offset), pos);
-
-	/* mov arg2, #reg_size */
-	ins(BPF_ALU64_IMM(BPF_MOV, BPF_REG_ARG2, BPF_REG_SIZE), pos);
-
-	/* mov arg1, dst_addr_reg */
-	if (dst_addr_reg != BPF_REG_ARG1)
-		ins(BPF_MOV64_REG(BPF_REG_ARG1, dst_addr_reg), pos);
-
-	/* Call probe_read  */
-	ins(BPF_EMIT_CALL(probeid), pos);
-	/*
-	 * Error processing: if read fail, goto error code,
-	 * will be relocated. Target should be the start of
-	 * error processing code.
-	 */
-	ins(BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, JMP_TO_ERROR_CODE),
-	    pos);
-
-	return check_pos(pos);
-}
-
-/*
- * Each arg should be bare register. Fetch and save them into argument
- * registers (r3 - r5).
- *
- * BPF_REG_1 should have been initialized with pointer to
- * 'struct pt_regs'.
- */
-static int
-gen_prologue_fastpath(struct bpf_insn_pos *pos,
-		      struct probe_trace_arg *args, int nargs)
-{
-	int i, err = 0;
-
-	for (i = 0; i < nargs; i++) {
-		err = gen_ldx_reg_from_ctx(pos, BPF_REG_1, args[i].value,
-					   BPF_PROLOGUE_START_ARG_REG + i);
-		if (err)
-			goto errout;
-	}
-
-	return check_pos(pos);
-errout:
-	return err;
-}
-
-/*
- * Slow path:
- *   At least one argument has the form of 'offset($rx)'.
- *
- * Following code first stores them into stack, then loads all of then
- * to r2 - r5.
- * Before final loading, the final result should be:
- *
- * low address
- * BPF_REG_FP - 24  ARG3
- * BPF_REG_FP - 16  ARG2
- * BPF_REG_FP - 8   ARG1
- * BPF_REG_FP
- * high address
- *
- * For each argument (described as: offn(...off2(off1(reg)))),
- * generates following code:
- *
- *  r7 <- fp
- *  r7 <- r7 - stack_offset  // Ideal code should initialize r7 using
- *                           // fp before generating args. However,
- *                           // eBPF won't regard r7 as stack pointer
- *                           // if it is generated by minus 8 from
- *                           // another stack pointer except fp.
- *                           // This is why we have to set r7
- *                           // to fp for each variable.
- *  r3 <- value of 'reg'-> generated using gen_ldx_reg_from_ctx()
- *  (r7) <- r3       // skip following instructions for bare reg
- *  r3 <- r3 + off1  . // skip if off1 == 0
- *  r2 <- 8           \
- *  r1 <- r7           |-> generated by gen_read_mem()
- *  call probe_read    /
- *  jnei r0, 0, err  ./
- *  r3 <- (r7)
- *  r3 <- r3 + off2  . // skip if off2 == 0
- *  r2 <- 8           \  // r2 may be broken by probe_read, so set again
- *  r1 <- r7           |-> generated by gen_read_mem()
- *  call probe_read    /
- *  jnei r0, 0, err  ./
- *  ...
- */
-static int
-gen_prologue_slowpath(struct bpf_insn_pos *pos,
-		      struct probe_trace_arg *args, int nargs)
-{
-	int err, i, probeid;
-
-	for (i = 0; i < nargs; i++) {
-		struct probe_trace_arg *arg = &args[i];
-		const char *reg = arg->value;
-		struct probe_trace_arg_ref *ref = NULL;
-		int stack_offset = (i + 1) * -8;
-
-		pr_debug("prologue: fetch arg %d, base reg is %s\n",
-			 i, reg);
-
-		/* value of base register is stored into ARG3 */
-		err = gen_ldx_reg_from_ctx(pos, BPF_REG_CTX, reg,
-					   BPF_REG_ARG3);
-		if (err) {
-			pr_err("prologue: failed to get offset of register %s\n",
-			       reg);
-			goto errout;
-		}
-
-		/* Make r7 the stack pointer. */
-		ins(BPF_MOV64_REG(BPF_REG_7, BPF_REG_FP), pos);
-		/* r7 += -8 */
-		ins(BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, stack_offset), pos);
-		/*
-		 * Store r3 (base register) onto stack
-		 * Ensure fp[offset] is set.
-		 * fp is the only valid base register when storing
-		 * into stack. We are not allowed to use r7 as base
-		 * register here.
-		 */
-		ins(BPF_STX_MEM(BPF_DW, BPF_REG_FP, BPF_REG_ARG3,
-				stack_offset), pos);
-
-		ref = arg->ref;
-		probeid = BPF_FUNC_probe_read_kernel;
-		while (ref) {
-			pr_debug("prologue: arg %d: offset %ld\n",
-				 i, ref->offset);
-
-			if (ref->user_access)
-				probeid = BPF_FUNC_probe_read_user;
-
-			err = gen_read_mem(pos, BPF_REG_3, BPF_REG_7,
-					   ref->offset, probeid);
-			if (err) {
-				pr_err("prologue: failed to generate probe_read function call\n");
-				goto errout;
-			}
-
-			ref = ref->next;
-			/*
-			 * Load previous result into ARG3. Use
-			 * BPF_REG_FP instead of r7 because verifier
-			 * allows FP based addressing only.
-			 */
-			if (ref)
-				ins(BPF_LDX_MEM(BPF_DW, BPF_REG_ARG3,
-						BPF_REG_FP, stack_offset), pos);
-		}
-	}
-
-	/* Final pass: read to registers */
-	for (i = 0; i < nargs; i++) {
-		int insn_sz = (args[i].ref) ? argtype_to_ldx_size(args[i].type) : BPF_DW;
-
-		pr_debug("prologue: load arg %d, insn_sz is %s\n",
-			 i, insn_sz_to_str(insn_sz));
-		ins(BPF_LDX_MEM(insn_sz, BPF_PROLOGUE_START_ARG_REG + i,
-				BPF_REG_FP, -BPF_REG_SIZE * (i + 1)), pos);
-	}
-
-	ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_SUCCESS_CODE), pos);
-
-	return check_pos(pos);
-errout:
-	return err;
-}
-
-static int
-prologue_relocate(struct bpf_insn_pos *pos, struct bpf_insn *error_code,
-		  struct bpf_insn *success_code, struct bpf_insn *user_code)
-{
-	struct bpf_insn *insn;
-
-	if (check_pos(pos))
-		return -BPF_LOADER_ERRNO__PROLOGUE2BIG;
-
-	for (insn = pos->begin; insn < pos->pos; insn++) {
-		struct bpf_insn *target;
-		u8 class = BPF_CLASS(insn->code);
-		u8 opcode;
-
-		if (class != BPF_JMP)
-			continue;
-		opcode = BPF_OP(insn->code);
-		if (opcode == BPF_CALL)
-			continue;
-
-		switch (insn->off) {
-		case JMP_TO_ERROR_CODE:
-			target = error_code;
-			break;
-		case JMP_TO_SUCCESS_CODE:
-			target = success_code;
-			break;
-		case JMP_TO_USER_CODE:
-			target = user_code;
-			break;
-		default:
-			pr_err("bpf prologue: internal error: relocation failed\n");
-			return -BPF_LOADER_ERRNO__PROLOGUE;
-		}
-
-		insn->off = target - (insn + 1);
-	}
-	return 0;
-}
-
-int bpf__gen_prologue(struct probe_trace_arg *args, int nargs,
-		      struct bpf_insn *new_prog, size_t *new_cnt,
-		      size_t cnt_space)
-{
-	struct bpf_insn *success_code = NULL;
-	struct bpf_insn *error_code = NULL;
-	struct bpf_insn *user_code = NULL;
-	struct bpf_insn_pos pos;
-	bool fastpath = true;
-	int err = 0, i;
-
-	if (!new_prog || !new_cnt)
-		return -EINVAL;
-
-	if (cnt_space > BPF_MAXINSNS)
-		cnt_space = BPF_MAXINSNS;
-
-	pos.begin = new_prog;
-	pos.end = new_prog + cnt_space;
-	pos.pos = new_prog;
-
-	if (!nargs) {
-		ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 0),
-		    &pos);
-
-		if (check_pos(&pos))
-			goto errout;
-
-		*new_cnt = pos_get_cnt(&pos);
-		return 0;
-	}
-
-	if (nargs > BPF_PROLOGUE_MAX_ARGS) {
-		pr_warning("bpf: prologue: %d arguments are dropped\n",
-			   nargs - BPF_PROLOGUE_MAX_ARGS);
-		nargs = BPF_PROLOGUE_MAX_ARGS;
-	}
-
-	/* First pass: validation */
-	for (i = 0; i < nargs; i++) {
-		struct probe_trace_arg_ref *ref = args[i].ref;
-
-		if (args[i].value[0] == '@') {
-			/* TODO: fetch global variable */
-			pr_err("bpf: prologue: global %s%+ld not support\n",
-				args[i].value, ref ? ref->offset : 0);
-			return -ENOTSUP;
-		}
-
-		while (ref) {
-			/* fastpath is true if all args has ref == NULL */
-			fastpath = false;
-
-			/*
-			 * Instruction encodes immediate value using
-			 * s32, ref->offset is long. On systems which
-			 * can't fill long in s32, refuse to process if
-			 * ref->offset too large (or small).
-			 */
-#ifdef __LP64__
-#define OFFSET_MAX	((1LL << 31) - 1)
-#define OFFSET_MIN	((1LL << 31) * -1)
-			if (ref->offset > OFFSET_MAX ||
-					ref->offset < OFFSET_MIN) {
-				pr_err("bpf: prologue: offset out of bound: %ld\n",
-				       ref->offset);
-				return -BPF_LOADER_ERRNO__PROLOGUEOOB;
-			}
-#endif
-			ref = ref->next;
-		}
-	}
-	pr_debug("prologue: pass validation\n");
-
-	if (fastpath) {
-		/* If all variables are registers... */
-		pr_debug("prologue: fast path\n");
-		err = gen_prologue_fastpath(&pos, args, nargs);
-		if (err)
-			goto errout;
-	} else {
-		pr_debug("prologue: slow path\n");
-
-		/* Initialization: move ctx to a callee saved register. */
-		ins(BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1), &pos);
-
-		err = gen_prologue_slowpath(&pos, args, nargs);
-		if (err)
-			goto errout;
-		/*
-		 * start of ERROR_CODE (only slow pass needs error code)
-		 *   mov r2 <- 1  // r2 is error number
-		 *   mov r3 <- 0  // r3, r4... should be touched or
-		 *                // verifier would complain
-		 *   mov r4 <- 0
-		 *   ...
-		 *   goto usercode
-		 */
-		error_code = pos.pos;
-		ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 1),
-		    &pos);
-
-		for (i = 0; i < nargs; i++)
-			ins(BPF_ALU64_IMM(BPF_MOV,
-					  BPF_PROLOGUE_START_ARG_REG + i,
-					  0),
-			    &pos);
-		ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_USER_CODE),
-				&pos);
-	}
-
-	/*
-	 * start of SUCCESS_CODE:
-	 *   mov r2 <- 0
-	 *   goto usercode  // skip
-	 */
-	success_code = pos.pos;
-	ins(BPF_ALU64_IMM(BPF_MOV, BPF_PROLOGUE_FETCH_RESULT_REG, 0), &pos);
-
-	/*
-	 * start of USER_CODE:
-	 *   Restore ctx to r1
-	 */
-	user_code = pos.pos;
-	if (!fastpath) {
-		/*
-		 * Only slow path needs restoring of ctx. In fast path,
-		 * register are loaded directly from r1.
-		 */
-		ins(BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX), &pos);
-		err = prologue_relocate(&pos, error_code, success_code,
-					user_code);
-		if (err)
-			goto errout;
-	}
-
-	err = check_pos(&pos);
-	if (err)
-		goto errout;
-
-	*new_cnt = pos_get_cnt(&pos);
-	return 0;
-errout:
-	return err;
-}
-- 
2.42.0.283.g2d96d420d3-goog

Re: [PATCH v1] perf bpf-prologue: Remove unused file

[Namhyung Kim]

On Wed, Sep 13, 2023 at 11:45 AM Ian Rogers <irogers@google.com> wrote:
>
> Commit 3d6dfae88917 ("perf parse-events: Remove BPF event support")
> removed building bpf-prologue.c but failed to remove the actual file.
>
> Fixes: 3d6dfae88917 ("perf parse-events: Remove BPF event support")
> Signed-off-by: Ian Rogers <irogers@google.com>

Applied to perf-tools, thanks!

Namhyung