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b_frontend_action.cc
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b_frontend_action.cc
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/*
* Copyright (c) 2015 PLUMgrid, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <linux/bpf.h>
#include <linux/version.h>
#include <sys/utsname.h>
#include <unistd.h>
#include <stdlib.h>
#include <clang/AST/ASTConsumer.h>
#include <clang/AST/ASTContext.h>
#include <clang/AST/RecordLayout.h>
#include <clang/Frontend/CompilerInstance.h>
#include <clang/Frontend/MultiplexConsumer.h>
#include <clang/Rewrite/Core/Rewriter.h>
#include <clang/Lex/Lexer.h>
#include "frontend_action_common.h"
#include "b_frontend_action.h"
#include "bpf_module.h"
#include "common.h"
#include "loader.h"
#include "table_storage.h"
#include "arch_helper.h"
#include "bcc_libbpf_inc.h"
#include "libbpf.h"
#include "bcc_syms.h"
namespace ebpf {
constexpr int MAX_CALLING_CONV_REGS = 6;
const char *calling_conv_regs_x86[] = {
"di", "si", "dx", "cx", "r8", "r9"
};
const char *calling_conv_syscall_regs_x86[] = {
"di", "si", "dx", "r10", "r8", "r9"
};
const char *calling_conv_regs_ppc[] = {"gpr[3]", "gpr[4]", "gpr[5]",
"gpr[6]", "gpr[7]", "gpr[8]"};
const char *calling_conv_regs_s390x[] = {"gprs[2]", "gprs[3]", "gprs[4]",
"gprs[5]", "gprs[6]" };
const char *calling_conv_regs_arm64[] = {"regs[0]", "regs[1]", "regs[2]",
"regs[3]", "regs[4]", "regs[5]"};
const char *calling_conv_regs_mips[] = {"regs[4]", "regs[5]", "regs[6]",
"regs[7]", "regs[8]", "regs[9]"};
const char *calling_conv_regs_riscv64[] = {"a0", "a1", "a2",
"a3", "a4", "a5"};
const char *calling_conv_regs_loongarch[] = {"regs[4]", "regs[5]", "regs[6]",
"regs[7]", "regs[8]", "regs[9]"};
void *get_call_conv_cb(bcc_arch_t arch, bool for_syscall)
{
const char **ret;
switch(arch) {
case BCC_ARCH_PPC:
case BCC_ARCH_PPC_LE:
ret = calling_conv_regs_ppc;
break;
case BCC_ARCH_S390X:
ret = calling_conv_regs_s390x;
break;
case BCC_ARCH_ARM64:
ret = calling_conv_regs_arm64;
break;
case BCC_ARCH_MIPS:
ret = calling_conv_regs_mips;
break;
case BCC_ARCH_RISCV64:
ret = calling_conv_regs_riscv64;
break;
case BCC_ARCH_LOONGARCH:
ret = calling_conv_regs_loongarch;
break;
default:
if (for_syscall)
ret = calling_conv_syscall_regs_x86;
else
ret = calling_conv_regs_x86;
}
return (void *)ret;
}
const char **get_call_conv(bool for_syscall = false) {
const char **ret;
ret = (const char **)run_arch_callback(get_call_conv_cb, for_syscall);
return ret;
}
/* Use resolver only once per translation */
static void *kresolver = NULL;
static void *get_symbol_resolver(void) {
if (!kresolver)
kresolver = bcc_symcache_new(-1, nullptr);
return kresolver;
}
static std::string check_bpf_probe_read_kernel(void) {
bool is_probe_read_kernel;
void *resolver = get_symbol_resolver();
uint64_t addr = 0;
is_probe_read_kernel = bcc_symcache_resolve_name(resolver, nullptr,
"bpf_probe_read_kernel", &addr) >= 0 ? true: false;
/* If bpf_probe_read is not found (ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) is
* not set in newer kernel, then bcc would anyway fail */
if (is_probe_read_kernel)
return "bpf_probe_read_kernel";
else
return "bpf_probe_read";
}
static std::string check_bpf_probe_read_user(llvm::StringRef probe,
bool& overlap_addr) {
if (probe.str() == "bpf_probe_read_user" ||
probe.str() == "bpf_probe_read_user_str") {
// Check for probe_user symbols in backported kernel before fallback
void *resolver = get_symbol_resolver();
uint64_t addr = 0;
bool found = bcc_symcache_resolve_name(resolver, nullptr,
"bpf_probe_read_user", &addr) >= 0 ? true: false;
if (found)
return probe.str();
/* For arch with overlapping address space, dont use bpf_probe_read for
* user read. Just error out */
#if defined(__s390x__)
overlap_addr = true;
return "";
#endif
if (probe.str() == "bpf_probe_read_user")
return "bpf_probe_read";
else
return "bpf_probe_read_str";
}
return "";
}
using std::map;
using std::move;
using std::set;
using std::tuple;
using std::make_tuple;
using std::string;
using std::to_string;
using std::unique_ptr;
using std::vector;
using namespace clang;
class ProbeChecker : public RecursiveASTVisitor<ProbeChecker> {
public:
explicit ProbeChecker(Expr *arg, const set<tuple<Decl *, int>> &ptregs,
bool track_helpers, bool is_assign)
: needs_probe_(false), is_transitive_(false), ptregs_(ptregs),
track_helpers_(track_helpers), nb_derefs_(0), is_assign_(is_assign) {
if (arg) {
TraverseStmt(arg);
if (arg->getType()->isPointerType())
is_transitive_ = needs_probe_;
}
}
explicit ProbeChecker(Expr *arg, const set<tuple<Decl *, int>> &ptregs,
bool is_transitive)
: ProbeChecker(arg, ptregs, is_transitive, false) {}
bool VisitCallExpr(CallExpr *E) {
needs_probe_ = false;
if (is_assign_) {
// We're looking for a function that returns an external pointer,
// regardless of the number of dereferences.
for(auto p : ptregs_) {
if (std::get<0>(p) == E->getDirectCallee()) {
needs_probe_ = true;
// ptregs_ stores the number of dereferences needed to get the external
// pointer, while nb_derefs_ stores the number of dereferences
// encountered. So, any dereference encountered is one less
// dereference needed to get the external pointer.
nb_derefs_ -= std::get<1>(p);
return false;
}
}
} else {
tuple<Decl *, int> pt = make_tuple(E->getDirectCallee(), nb_derefs_);
if (ptregs_.find(pt) != ptregs_.end())
needs_probe_ = true;
}
if (!track_helpers_)
return false;
if (VarDecl *V = dyn_cast<VarDecl>(E->getCalleeDecl()))
needs_probe_ = V->getName() == "bpf_get_current_task";
return false;
}
bool VisitMemberExpr(MemberExpr *M) {
tuple<Decl *, int> pt = make_tuple(M->getMemberDecl(), nb_derefs_);
if (ptregs_.find(pt) != ptregs_.end()) {
needs_probe_ = true;
return false;
}
if (M->isArrow()) {
/* In A->b, if A is an external pointer, then A->b should be considered
* one too. However, if we're taking the address of A->b
* (nb_derefs_ < 0), we should take it into account for the number of
* indirections; &A->b is a pointer to A with an offset. */
if (nb_derefs_ >= 0) {
ProbeChecker checker = ProbeChecker(M->getBase(), ptregs_,
track_helpers_, is_assign_);
if (checker.needs_probe() && checker.get_nb_derefs() == 0) {
needs_probe_ = true;
return false;
}
}
nb_derefs_++;
}
return true;
}
bool VisitUnaryOperator(UnaryOperator *E) {
if (E->getOpcode() == UO_Deref) {
/* In *A, if A is an external pointer, then *A should be considered one
* too. */
ProbeChecker checker = ProbeChecker(E->getSubExpr(), ptregs_,
track_helpers_, is_assign_);
if (checker.needs_probe() && checker.get_nb_derefs() == 0) {
needs_probe_ = true;
return false;
}
nb_derefs_++;
} else if (E->getOpcode() == UO_AddrOf) {
nb_derefs_--;
}
return true;
}
bool VisitDeclRefExpr(DeclRefExpr *E) {
if (is_assign_) {
// We're looking for an external pointer, regardless of the number of
// dereferences.
for(auto p : ptregs_) {
if (std::get<0>(p) == E->getDecl()) {
needs_probe_ = true;
// ptregs_ stores the number of dereferences needed to get the external
// pointer, while nb_derefs_ stores the number of dereferences
// encountered. So, any dereference encountered is one less
// dereference needed to get the external pointer.
nb_derefs_ -= std::get<1>(p);
return false;
}
}
} else {
tuple<Decl *, int> pt = make_tuple(E->getDecl(), nb_derefs_);
if (ptregs_.find(pt) != ptregs_.end())
needs_probe_ = true;
}
return true;
}
bool needs_probe() const { return needs_probe_; }
bool is_transitive() const { return is_transitive_; }
int get_nb_derefs() const { return nb_derefs_; }
private:
bool needs_probe_;
bool is_transitive_;
const set<tuple<Decl *, int>> &ptregs_;
bool track_helpers_;
// Nb of dereferences we go through before finding the external pointer.
// A negative number counts the number of addrof.
int nb_derefs_;
bool is_assign_;
};
// Visit a piece of the AST and mark it as needing probe reads
class ProbeSetter : public RecursiveASTVisitor<ProbeSetter> {
public:
explicit ProbeSetter(set<tuple<Decl *, int>> *ptregs, int nb_derefs)
: ptregs_(ptregs), nb_derefs_(nb_derefs) {}
bool VisitDeclRefExpr(DeclRefExpr *E) {
tuple<Decl *, int> pt = make_tuple(E->getDecl(), nb_derefs_);
ptregs_->insert(pt);
return true;
}
explicit ProbeSetter(set<tuple<Decl *, int>> *ptregs)
: ProbeSetter(ptregs, 0) {}
bool VisitUnaryOperator(UnaryOperator *E) {
if (E->getOpcode() == UO_Deref)
nb_derefs_++;
return true;
}
bool VisitMemberExpr(MemberExpr *M) {
tuple<Decl *, int> pt = make_tuple(M->getMemberDecl(), nb_derefs_);
ptregs_->insert(pt);
return false;
}
private:
set<tuple<Decl *, int>> *ptregs_;
// Nb of dereferences we go through before getting to the actual variable.
int nb_derefs_;
};
MapVisitor::MapVisitor(set<Decl *> &m) : m_(m) {}
bool MapVisitor::VisitCallExpr(CallExpr *Call) {
if (MemberExpr *Memb = dyn_cast<MemberExpr>(Call->getCallee()->IgnoreImplicit())) {
StringRef memb_name = Memb->getMemberDecl()->getName();
if (DeclRefExpr *Ref = dyn_cast<DeclRefExpr>(Memb->getBase())) {
if (SectionAttr *A = Ref->getDecl()->getAttr<SectionAttr>()) {
if (!A->getName().startswith("maps"))
return true;
if (memb_name == "update" || memb_name == "insert") {
ProbeChecker checker = ProbeChecker(Call->getArg(1), ptregs_, true,
true);
if (checker.needs_probe())
m_.insert(Ref->getDecl());
}
}
}
}
return true;
}
ProbeVisitor::ProbeVisitor(ASTContext &C, Rewriter &rewriter,
set<Decl *> &m, bool track_helpers) :
C(C), rewriter_(rewriter), m_(m), ctx_(nullptr), track_helpers_(track_helpers),
addrof_stmt_(nullptr), is_addrof_(false) {
const char **calling_conv_regs = get_call_conv();
cannot_fall_back_safely = (calling_conv_regs == calling_conv_regs_s390x || calling_conv_regs == calling_conv_regs_riscv64);
}
bool ProbeVisitor::assignsExtPtr(Expr *E, int *nbDerefs) {
if (IsContextMemberExpr(E)) {
*nbDerefs = 0;
return true;
}
/* If the expression contains a call to another function, we need to visit
* that function first to know if a rewrite is necessary (i.e., if the
* function returns an external pointer). */
if (!TraverseStmt(E))
return false;
ProbeChecker checker = ProbeChecker(E, ptregs_, track_helpers_,
true);
if (checker.is_transitive()) {
// The negative of the number of dereferences is the number of addrof. In
// an assignment, if we went through n addrof before getting the external
// pointer, then we'll need n dereferences on the left-hand side variable
// to get to the external pointer.
*nbDerefs = -checker.get_nb_derefs();
return true;
}
if (E->IgnoreParenCasts()->getStmtClass() == Stmt::CallExprClass) {
CallExpr *Call = dyn_cast<CallExpr>(E->IgnoreParenCasts());
if (MemberExpr *Memb = dyn_cast<MemberExpr>(Call->getCallee()->IgnoreImplicit())) {
StringRef memb_name = Memb->getMemberDecl()->getName();
if (DeclRefExpr *Ref = dyn_cast<DeclRefExpr>(Memb->getBase())) {
if (SectionAttr *A = Ref->getDecl()->getAttr<SectionAttr>()) {
if (!A->getName().startswith("maps"))
return false;
if (memb_name == "lookup" || memb_name == "lookup_or_init" ||
memb_name == "lookup_or_try_init") {
if (m_.find(Ref->getDecl()) != m_.end()) {
// Retrieved an ext. pointer from a map, mark LHS as ext. pointer.
// Pointers from maps always need a single dereference to get the
// actual value. The value may be an external pointer but cannot
// be a pointer to an external pointer as the verifier prohibits
// storing known pointers (to map values, context, the stack, or
// the packet) in maps.
*nbDerefs = 1;
return true;
}
}
}
}
}
}
return false;
}
bool ProbeVisitor::VisitVarDecl(VarDecl *D) {
if (Expr *E = D->getInit()) {
int nbDerefs;
if (assignsExtPtr(E, &nbDerefs)) {
// The negative of the number of addrof is the number of dereferences.
tuple<Decl *, int> pt = make_tuple(D, nbDerefs);
set_ptreg(pt);
}
}
return true;
}
bool ProbeVisitor::TraverseStmt(Stmt *S) {
if (whitelist_.find(S) != whitelist_.end())
return true;
auto ret = RecursiveASTVisitor<ProbeVisitor>::TraverseStmt(S);
if (addrof_stmt_ == S) {
addrof_stmt_ = nullptr;
is_addrof_ = false;
}
return ret;
}
bool ProbeVisitor::VisitCallExpr(CallExpr *Call) {
// Skip bpf_probe_read for the third argument if it is an AddrOf.
if (VarDecl *V = dyn_cast<VarDecl>(Call->getCalleeDecl())) {
if (V->getName() == "bpf_probe_read" && Call->getNumArgs() >= 3) {
const Expr *E = Call->getArg(2)->IgnoreParenCasts();
whitelist_.insert(E);
return true;
}
}
if (FunctionDecl *F = dyn_cast<FunctionDecl>(Call->getCalleeDecl())) {
if (F->hasBody()) {
unsigned i = 0;
for (auto arg : Call->arguments()) {
ProbeChecker checker = ProbeChecker(arg, ptregs_, track_helpers_,
true);
if (checker.needs_probe()) {
tuple<Decl *, int> pt = make_tuple(F->getParamDecl(i),
-checker.get_nb_derefs());
ptregs_.insert(pt);
}
++i;
}
if (fn_visited_.find(F) == fn_visited_.end()) {
fn_visited_.insert(F);
/* Maintains a stack of the number of dereferences for the external
* pointers returned by each function in the call stack or -1 if the
* function didn't return an external pointer. */
ptregs_returned_.push_back(-1);
TraverseDecl(F);
int nb_derefs = ptregs_returned_.back();
ptregs_returned_.pop_back();
if (nb_derefs != -1) {
tuple<Decl *, int> pt = make_tuple(F, nb_derefs);
ptregs_.insert(pt);
}
}
}
}
return true;
}
bool ProbeVisitor::VisitReturnStmt(ReturnStmt *R) {
/* If this function wasn't called by another, there's no need to check the
* return statement for external pointers. */
if (ptregs_returned_.size() == 0)
return true;
/* Reverse order of traversals. This is needed if, in the return statement,
* we're calling a function that's returning an external pointer: we need to
* know what the function is returning to decide what this function is
* returning. */
if (!TraverseStmt(R->getRetValue()))
return false;
ProbeChecker checker = ProbeChecker(R->getRetValue(), ptregs_,
track_helpers_, true);
if (checker.needs_probe()) {
int curr_nb_derefs = ptregs_returned_.back();
int nb_derefs = -checker.get_nb_derefs();
/* If the function returns external pointers with different levels of
* indirection, we handle the case with the highest level of indirection
* and leave it to the user to manually handle other cases. */
if (nb_derefs > curr_nb_derefs) {
ptregs_returned_.pop_back();
ptregs_returned_.push_back(nb_derefs);
}
}
return true;
}
bool ProbeVisitor::VisitBinaryOperator(BinaryOperator *E) {
if (!E->isAssignmentOp())
return true;
// copy probe attribute from RHS to LHS if present
int nbDerefs;
if (assignsExtPtr(E->getRHS(), &nbDerefs)) {
ProbeSetter setter(&ptregs_, nbDerefs);
setter.TraverseStmt(E->getLHS());
}
return true;
}
bool ProbeVisitor::VisitUnaryOperator(UnaryOperator *E) {
if (E->getOpcode() == UO_AddrOf) {
addrof_stmt_ = E;
is_addrof_ = true;
}
if (E->getOpcode() != UO_Deref)
return true;
if (memb_visited_.find(E) != memb_visited_.end())
return true;
Expr *sub = E->getSubExpr();
if (!ProbeChecker(sub, ptregs_, track_helpers_).needs_probe())
return true;
memb_visited_.insert(E);
string pre, post;
pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
if (cannot_fall_back_safely)
pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)";
else
pre += " bpf_probe_read(&_val, sizeof(_val), (u64)";
post = "); _val; })";
rewriter_.ReplaceText(expansionLoc(E->getOperatorLoc()), 1, pre);
rewriter_.InsertTextAfterToken(expansionLoc(GET_ENDLOC(sub)), post);
return true;
}
bool ProbeVisitor::VisitMemberExpr(MemberExpr *E) {
if (memb_visited_.find(E) != memb_visited_.end()) return true;
Expr *base;
SourceLocation rhs_start, member;
bool found = false;
for (MemberExpr *M = E; M; M = dyn_cast<MemberExpr>(M->getBase())) {
memb_visited_.insert(M);
rhs_start = GET_ENDLOC(M);
base = M->getBase();
member = M->getMemberLoc();
if (M->isArrow()) {
found = true;
break;
}
}
if (!found)
return true;
if (member.isInvalid()) {
error(GET_ENDLOC(base), "internal error: MemberLoc is invalid while preparing probe rewrite");
return false;
}
if (!rewriter_.isRewritable(GET_BEGINLOC(E)))
return true;
// parent expr has addrof, skip the rewrite, set is_addrof_ to flase so
// it won't affect next level of indirect address
if (is_addrof_) {
is_addrof_ = false;
return true;
}
/* If the base of the dereference is a call to another function, we need to
* visit that function first to know if a rewrite is necessary (i.e., if the
* function returns an external pointer). */
if (base->IgnoreParenCasts()->getStmtClass() == Stmt::CallExprClass) {
CallExpr *Call = dyn_cast<CallExpr>(base->IgnoreParenCasts());
if (!TraverseStmt(Call))
return false;
}
// Checks to see if the expression references something that needs to be run
// through bpf_probe_read.
if (!ProbeChecker(base, ptregs_, track_helpers_).needs_probe())
return true;
// If the base is an array, we will skip rewriting. See issue #2352.
if (E->getType()->isArrayType())
return true;
string rhs = rewriter_.getRewrittenText(expansionRange(SourceRange(rhs_start, GET_ENDLOC(E))));
string base_type = base->getType()->getPointeeType().getAsString();
string pre, post;
pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
if (cannot_fall_back_safely)
pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)&";
else
pre += " bpf_probe_read(&_val, sizeof(_val), (u64)&";
post = rhs + "); _val; })";
rewriter_.InsertText(expansionLoc(GET_BEGINLOC(E)), pre);
rewriter_.ReplaceText(expansionRange(SourceRange(member, GET_ENDLOC(E))), post);
return true;
}
bool ProbeVisitor::VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
if (memb_visited_.find(E) != memb_visited_.end()) return true;
if (!ProbeChecker(E, ptregs_, track_helpers_).needs_probe())
return true;
// Parent expr has addrof, skip the rewrite.
if (is_addrof_)
return true;
// If the base is an array, we will skip rewriting. See issue #2352.
if (E->getType()->isArrayType())
return true;
if (!rewriter_.isRewritable(GET_BEGINLOC(E)))
return true;
Expr *base = E->getBase();
Expr *idx = E->getIdx();
memb_visited_.insert(E);
if (!rewriter_.isRewritable(GET_BEGINLOC(base)))
return true;
if (!rewriter_.isRewritable(GET_BEGINLOC(idx)))
return true;
string pre, lbracket, rbracket;
LangOptions opts;
SourceLocation lbracket_start, lbracket_end;
SourceRange lbracket_range;
/* For cases like daddr->s6_addr[4], clang encodes the end location of "base"
* as "]". This makes it hard to rewrite the expression like
* "daddr->s6_addr [ 4 ]" since we do not know the end location
* of "addr->s6_addr". Let us abort the operation if this is the case.
*/
lbracket_start = Lexer::getLocForEndOfToken(GET_ENDLOC(base), 1,
rewriter_.getSourceMgr(),
opts).getLocWithOffset(1);
lbracket_end = GET_BEGINLOC(idx).getLocWithOffset(-1);
lbracket_range = expansionRange(SourceRange(lbracket_start, lbracket_end));
if (rewriter_.getRewrittenText(lbracket_range).size() == 0)
return true;
pre = "({ typeof(" + E->getType().getAsString() + ") _val; __builtin_memset(&_val, 0, sizeof(_val));";
if (cannot_fall_back_safely)
pre += " bpf_probe_read_kernel(&_val, sizeof(_val), (u64)((";
else
pre += " bpf_probe_read(&_val, sizeof(_val), (u64)((";
if (isMemberDereference(base)) {
pre += "&";
// If the base of the array subscript is a member dereference, we'll rewrite
// both at the same time.
addrof_stmt_ = base;
is_addrof_ = true;
}
rewriter_.InsertText(expansionLoc(GET_BEGINLOC(base)), pre);
/* Replace left bracket and any space around it. Since Clang doesn't provide
* a method to retrieve the left bracket, replace everything from the end of
* the base to the start of the index. */
lbracket = ") + (";
rewriter_.ReplaceText(lbracket_range, lbracket);
rbracket = "))); _val; })";
rewriter_.ReplaceText(expansionLoc(E->getRBracketLoc()), 1, rbracket);
return true;
}
bool ProbeVisitor::isMemberDereference(Expr *E) {
if (E->IgnoreParenCasts()->getStmtClass() != Stmt::MemberExprClass)
return false;
for (MemberExpr *M = dyn_cast<MemberExpr>(E->IgnoreParenCasts()); M;
M = dyn_cast<MemberExpr>(M->getBase()->IgnoreParenCasts())) {
if (M->isArrow())
return true;
}
return false;
}
bool ProbeVisitor::IsContextMemberExpr(Expr *E) {
if (!E->getType()->isPointerType())
return false;
Expr *base;
SourceLocation member;
bool found = false;
MemberExpr *M;
Expr *Ex = E->IgnoreParenCasts();
while (Ex->getStmtClass() == Stmt::ArraySubscriptExprClass
|| Ex->getStmtClass() == Stmt::MemberExprClass) {
if (Ex->getStmtClass() == Stmt::ArraySubscriptExprClass) {
Ex = dyn_cast<ArraySubscriptExpr>(Ex)->getBase()->IgnoreParenCasts();
} else if (Ex->getStmtClass() == Stmt::MemberExprClass) {
M = dyn_cast<MemberExpr>(Ex);
base = M->getBase()->IgnoreParenCasts();
member = M->getMemberLoc();
if (M->isArrow()) {
found = true;
break;
}
Ex = base;
}
}
if (!found) {
return false;
}
if (member.isInvalid()) {
return false;
}
if (DeclRefExpr *base_expr = dyn_cast<DeclRefExpr>(base)) {
if (base_expr->getDecl() == ctx_) {
return true;
}
}
return false;
}
SourceRange
ProbeVisitor::expansionRange(SourceRange range) {
#if LLVM_MAJOR_VERSION >= 7
return rewriter_.getSourceMgr().getExpansionRange(range).getAsRange();
#else
return rewriter_.getSourceMgr().getExpansionRange(range);
#endif
}
SourceLocation
ProbeVisitor::expansionLoc(SourceLocation loc) {
return rewriter_.getSourceMgr().getExpansionLoc(loc);
}
template <unsigned N>
DiagnosticBuilder ProbeVisitor::error(SourceLocation loc, const char (&fmt)[N]) {
unsigned int diag_id = C.getDiagnostics().getCustomDiagID(DiagnosticsEngine::Error, fmt);
return C.getDiagnostics().Report(loc, diag_id);
}
BTypeVisitor::BTypeVisitor(ASTContext &C, BFrontendAction &fe)
: C(C), diag_(C.getDiagnostics()), fe_(fe), rewriter_(fe.rewriter()), out_(llvm::errs()) {
const char **calling_conv_regs = get_call_conv();
cannot_fall_back_safely = (calling_conv_regs == calling_conv_regs_s390x || calling_conv_regs == calling_conv_regs_riscv64);
}
void BTypeVisitor::genParamDirectAssign(FunctionDecl *D, string& preamble,
const char **calling_conv_regs) {
for (size_t idx = 0; idx < fn_args_.size(); idx++) {
ParmVarDecl *arg = fn_args_[idx];
if (idx >= 1) {
// Move the args into a preamble section where the same params are
// declared and initialized from pt_regs.
// Todo: this init should be done only when the program requests it.
string text = rewriter_.getRewrittenText(expansionRange(arg->getSourceRange()));
arg->addAttr(UnavailableAttr::CreateImplicit(C, "ptregs"));
size_t d = idx - 1;
const char *reg = calling_conv_regs[d];
preamble += " " + text + " = " + fn_args_[0]->getName().str() + "->" +
string(reg) + ";";
}
}
}
void BTypeVisitor::genParamIndirectAssign(FunctionDecl *D, string& preamble,
const char **calling_conv_regs) {
string new_ctx;
for (size_t idx = 0; idx < fn_args_.size(); idx++) {
ParmVarDecl *arg = fn_args_[idx];
if (idx == 0) {
new_ctx = "__" + arg->getName().str();
preamble += " struct pt_regs * " + new_ctx + " = " +
arg->getName().str() + "->" +
string(calling_conv_regs[0]) + ";";
} else {
// Move the args into a preamble section where the same params are
// declared and initialized from pt_regs.
// Todo: this init should be done only when the program requests it.
string text = rewriter_.getRewrittenText(expansionRange(arg->getSourceRange()));
size_t d = idx - 1;
const char *reg = calling_conv_regs[d];
preamble += "\n " + text + ";";
if (cannot_fall_back_safely)
preamble += " bpf_probe_read_kernel";
else
preamble += " bpf_probe_read";
preamble += "(&" + arg->getName().str() + ", sizeof(" +
arg->getName().str() + "), &" + new_ctx + "->" +
string(reg) + ");";
}
}
}
void BTypeVisitor::rewriteFuncParam(FunctionDecl *D) {
string preamble = "{\n";
if (D->param_size() > 1) {
bool is_syscall = false;
if (strncmp(D->getName().str().c_str(), "syscall__", 9) == 0 ||
strncmp(D->getName().str().c_str(), "kprobe____x64_sys_", 18) == 0)
is_syscall = true;
const char **calling_conv_regs = get_call_conv(is_syscall);
// If function prefix is "syscall__" or "kprobe____x64_sys_",
// the function will attach to a kprobe syscall function.
// Guard parameter assiggnment with CONFIG_ARCH_HAS_SYSCALL_WRAPPER.
// For __x64_sys_* syscalls, this is always true, but we guard
// it in case of "syscall__" for other architectures.
if (is_syscall) {
preamble += "#if defined(CONFIG_ARCH_HAS_SYSCALL_WRAPPER) && !defined(__s390x__)\n";
genParamIndirectAssign(D, preamble, calling_conv_regs);
preamble += "\n#else\n";
genParamDirectAssign(D, preamble, calling_conv_regs);
preamble += "\n#endif\n";
} else {
genParamDirectAssign(D, preamble, calling_conv_regs);
}
rewriter_.ReplaceText(
expansionRange(SourceRange(GET_ENDLOC(D->getParamDecl(0)),
GET_ENDLOC(D->getParamDecl(D->getNumParams() - 1)))),
fn_args_[0]->getName());
}
// for each trace argument, convert the variable from ptregs to something on stack
if (CompoundStmt *S = dyn_cast<CompoundStmt>(D->getBody()))
rewriter_.ReplaceText(S->getLBracLoc(), 1, preamble);
}
bool BTypeVisitor::VisitFunctionDecl(FunctionDecl *D) {
// put each non-static non-inline function decl in its own section, to be
// extracted by the MemoryManager
auto real_start_loc = rewriter_.getSourceMgr().getFileLoc(GET_BEGINLOC(D));
if (fe_.is_rewritable_ext_func(D)) {
current_fn_ = string(D->getName());
string bd = rewriter_.getRewrittenText(expansionRange(D->getSourceRange()));
auto func_info = fe_.prog_func_info_.add_func(current_fn_);
if (!func_info) {
// We should only reach add_func above once per function seen, but the
// BPF_PROG-helper using macros in export/helpers.h (KFUNC_PROBE ..
// LSM_PROBE) break this logic. TODO: adjust export/helpers.h to not
// do so and bail out here, or find a better place to do add_func
func_info = fe_.prog_func_info_.get_func(current_fn_);
//error(GET_BEGINLOC(D), "redefinition of existing function");
//return false;
}
func_info->src_ = bd;
fe_.func_range_[current_fn_] = expansionRange(D->getSourceRange());
if (!D->getAttr<SectionAttr>()) {
string attr = string("__attribute__((section(\"") + BPF_FN_PREFIX +
D->getName().str() + "\")))\n";
rewriter_.InsertText(real_start_loc, attr);
}
if (D->param_size() > MAX_CALLING_CONV_REGS + 1) {
error(GET_BEGINLOC(D->getParamDecl(MAX_CALLING_CONV_REGS + 1)),
"too many arguments, bcc only supports in-register parameters");
return false;
}
fn_args_.clear();
for (auto arg_it = D->param_begin(); arg_it != D->param_end(); arg_it++) {
auto *arg = *arg_it;
if (arg->getName() == "") {
error(GET_ENDLOC(arg), "arguments to BPF program definition must be named");
return false;
}
fn_args_.push_back(arg);
}
rewriteFuncParam(D);
} else if (D->hasBody() &&
rewriter_.getSourceMgr().getFileID(real_start_loc)
== rewriter_.getSourceMgr().getMainFileID()) {
// rewritable functions that are static should be always treated as helper
rewriter_.InsertText(real_start_loc, "__attribute__((always_inline))\n");
}
return true;
}
// Reverse the order of call traversal so that parameters inside of
// function calls will get rewritten before the call itself, otherwise
// text mangling will result.
bool BTypeVisitor::TraverseCallExpr(CallExpr *Call) {
for (auto child : Call->children())
if (!TraverseStmt(child))
return false;
if (!WalkUpFromCallExpr(Call))
return false;
return true;
}
// convert calls of the type:
// table.foo(&key)
// to:
// bpf_table_foo_elem(bpf_pseudo_fd(table), &key [,&leaf])
bool BTypeVisitor::VisitCallExpr(CallExpr *Call) {
// make sure node is a reference to a bpf table, which is assured by the
// presence of the section("maps/<typename>") GNU __attribute__
if (MemberExpr *Memb = dyn_cast<MemberExpr>(Call->getCallee()->IgnoreImplicit())) {
StringRef memb_name = Memb->getMemberDecl()->getName();
if (DeclRefExpr *Ref = dyn_cast<DeclRefExpr>(Memb->getBase())) {
if (SectionAttr *A = Ref->getDecl()->getAttr<SectionAttr>()) {
if (!A->getName().startswith("maps"))
return true;
string args = rewriter_.getRewrittenText(expansionRange(SourceRange(GET_BEGINLOC(Call->getArg(0)),
GET_ENDLOC(Call->getArg(Call->getNumArgs() - 1)))));
// find the table fd, which was opened at declaration time
TableStorage::iterator desc;
Path local_path({fe_.id(), string(Ref->getDecl()->getName())});
Path global_path({string(Ref->getDecl()->getName())});
if (!fe_.table_storage().Find(local_path, desc)) {
if (!fe_.table_storage().Find(global_path, desc)) {
error(GET_ENDLOC(Ref), "bpf_table %0 failed to open") << Ref->getDecl()->getName();
return false;
}
}
string fd = to_string(desc->second.fd >= 0 ? desc->second.fd : desc->second.fake_fd);
string prefix, suffix;
string txt;
auto rewrite_start = GET_BEGINLOC(Call);
auto rewrite_end = GET_ENDLOC(Call);
if (memb_name == "lookup_or_init" || memb_name == "lookup_or_try_init") {
string name = string(Ref->getDecl()->getName());
string arg0 = rewriter_.getRewrittenText(expansionRange(Call->getArg(0)->getSourceRange()));
string arg1 = rewriter_.getRewrittenText(expansionRange(Call->getArg(1)->getSourceRange()));
string lookup = "bpf_map_lookup_elem_(bpf_pseudo_fd(1, " + fd + ")";
string update = "bpf_map_update_elem_(bpf_pseudo_fd(1, " + fd + ")";
txt = "({typeof(" + name + ".leaf) *leaf = " + lookup + ", " + arg0 + "); ";
txt += "if (!leaf) {";
txt += " " + update + ", " + arg0 + ", " + arg1 + ", BPF_NOEXIST);";
txt += " leaf = " + lookup + ", " + arg0 + ");";
if (memb_name == "lookup_or_init") {
txt += " if (!leaf) return 0;";
}
txt += "}";
txt += "leaf;})";
} else if (memb_name == "increment" || memb_name == "atomic_increment") {
string name = string(Ref->getDecl()->getName());
string arg0 = rewriter_.getRewrittenText(expansionRange(Call->getArg(0)->getSourceRange()));
string increment_value = "1";
if (Call->getNumArgs() == 2) {
increment_value = rewriter_.getRewrittenText(expansionRange(Call->getArg(1)->getSourceRange()));
}
string lookup = "bpf_map_lookup_elem_(bpf_pseudo_fd(1, " + fd + ")";
string update = "bpf_map_update_elem_(bpf_pseudo_fd(1, " + fd + ")";
txt = "({ typeof(" + name + ".key) _key = " + arg0 + "; ";
txt += "typeof(" + name + ".leaf) *_leaf = " + lookup + ", &_key); ";
txt += "if (_leaf) ";
if (memb_name == "atomic_increment") {
txt += "lock_xadd(_leaf, " + increment_value + ");";
} else {
txt += "(*_leaf) += " + increment_value + ";";
}
if (desc->second.type == BPF_MAP_TYPE_HASH) {
txt += "else { typeof(" + name + ".leaf) _zleaf; __builtin_memset(&_zleaf, 0, sizeof(_zleaf)); ";
txt += "_zleaf += " + increment_value + ";";
txt += update + ", &_key, &_zleaf, BPF_NOEXIST); } ";
}
txt += "})";
} else if (memb_name == "perf_submit") {
string name = string(Ref->getDecl()->getName());
string arg0 = rewriter_.getRewrittenText(expansionRange(Call->getArg(0)->getSourceRange()));
string args_other = rewriter_.getRewrittenText(expansionRange(SourceRange(GET_BEGINLOC(Call->getArg(1)),
GET_ENDLOC(Call->getArg(2)))));
txt = "bpf_perf_event_output(" + arg0 + ", bpf_pseudo_fd(1, " + fd + ")";
txt += ", CUR_CPU_IDENTIFIER, " + args_other + ")";
// e.g.
// struct data_t { u32 pid; }; data_t data;
// events.perf_submit(ctx, &data, sizeof(data));
// ...
// &data -> data -> typeof(data) -> data_t
auto type_arg1 = Call->getArg(1)->IgnoreCasts()->getType().getTypePtr()->getPointeeType().getTypePtrOrNull();
if (type_arg1 && type_arg1->isStructureType()) {
auto event_type = type_arg1->getAsTagDecl();
const auto *r = dyn_cast<RecordDecl>(event_type);
std::vector<std::string> perf_event;
for (auto it = r->field_begin(); it != r->field_end(); ++it) {
// After LLVM commit aee49255074f
// (https://github.com/llvm/llvm-project/commit/aee49255074fd4ef38d97e6e70cbfbf2f9fd0fa7)
// array type change from `comm#char [16]` to `comm#char[16]`
perf_event.push_back(it->getNameAsString() + "#" + it->getType().getAsString()); //"pid#u32"
}
fe_.perf_events_[name] = perf_event;
}
} else if (memb_name == "perf_submit_skb") {
string skb = rewriter_.getRewrittenText(expansionRange(Call->getArg(0)->getSourceRange()));
string skb_len = rewriter_.getRewrittenText(expansionRange(Call->getArg(1)->getSourceRange()));
string meta = rewriter_.getRewrittenText(expansionRange(Call->getArg(2)->getSourceRange()));
string meta_len = rewriter_.getRewrittenText(expansionRange(Call->getArg(3)->getSourceRange()));
txt = "bpf_perf_event_output(" +
skb + ", " +
"bpf_pseudo_fd(1, " + fd + "), " +
"((__u64)" + skb_len + " << 32) | BPF_F_CURRENT_CPU, " +
meta + ", " +
meta_len + ");";
} else if (memb_name == "get_stackid") {
if (desc->second.type == BPF_MAP_TYPE_STACK_TRACE) {
string arg0 =
rewriter_.getRewrittenText(expansionRange(Call->getArg(0)->getSourceRange()));
txt = "bcc_get_stackid(";
txt += "bpf_pseudo_fd(1, " + fd + "), " + arg0;
rewrite_end = GET_ENDLOC(Call->getArg(0));
} else {