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Get --ftrace working on aarch64
This change implements a new approach to function call logging, that's based on the GCC flag: -fpatchable-function-entry. Read the commentary in build/config.mk to learn how it works.
This commit is contained in:
Justine Tunney
parent
5b908bc756
commit
eb40cb371d
934 changed files with 2259 additions and 1268 deletions
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@ -18,99 +18,114 @@
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "ape/sections.internal.h"
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#include "libc/calls/struct/sigset.h"
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#include "libc/limits.h"
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#include "libc/macros.internal.h"
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#include "libc/runtime/morph.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/symbols.internal.h"
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#ifdef __x86_64__
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typedef uint8_t code_t;
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#elif defined(__aarch64__)
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typedef uint32_t code_t;
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#else
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#error "unsupported architecture"
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#endif
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static privileged bool IsVirginFunction(const code_t *func) {
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#ifdef __x86_64__
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long i;
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// function must be preceeded by 9 nops
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for (i = -9; i < 0; ++i) {
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if (func[i] != 0x90) return false;
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}
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// function must start with `nop nop` or `xchg %ax,%ax`
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if (func[0] == 0x90 && func[1] == 0x90) return true;
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if (func[0] == 0x66 && func[1] == 0x90) return true;
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return false;
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#elif defined(__aarch64__)
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long i;
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// function must be preceeded by 6 nops
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for (i = -6; i < 0; ++i) {
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if (func[i] != 0xd503201f) return false;
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}
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// function must start with one nop
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return func[0] == 0xd503201f;
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#endif
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}
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static privileged void HookFunction(code_t *func, void *dest) {
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long dp;
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#ifdef __x86_64__
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dp = (intptr_t)dest - (intptr_t)(func - 7 + 5);
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if (!(INT32_MIN <= dp && dp <= INT32_MAX)) return;
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// emit `ud2` signature for safety and checkability
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func[-9] = 0x0f;
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func[-8] = 0x0b;
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// emit `call dest` instruction
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func[-7] = 0xe8;
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func[-6] = dp;
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func[-5] = dp >> 8;
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func[-4] = dp >> 16;
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func[-3] = dp >> 24;
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// emit `jmp +2` instruction to re-enter hooked function
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func[-2] = 0xeb;
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func[-1] = 0x02;
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// emit `jmp -2` instruction to enter detour
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func[+0] = 0xeb;
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func[+1] = -7 - 2;
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#elif defined(__aarch64__)
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dp = (code_t *)dest - (func - 3);
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if (!(-33554432 <= dp && dp <= +33554431)) return;
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func[-6] = 0xd4200000 | (31337 << 5); // brk #31337
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func[-5] = 0xa9bf7bfd; // stp x29,x30,[sp, #-16]!
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func[-4] = 0x910003fd; // mov x29,sp
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func[-3] = 0x94000000 | (dp & 0x03ffffff); // bl dest
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func[-2] = 0xa8c17bfd; // ldp x29,x30,[sp], #16
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func[-1] = 0x14000000 | (+2 & 0x03ffffff); // b +1
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func[+0] = 0x14000000 | (-5 & 0x03ffffff); // b -5
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#endif
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}
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/**
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* Rewrites code in memory to hook function calls.
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*
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* We do this by searching each function for the nop instruction
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* inserted by GCC when we use the -pg -mnop-mcount flags. There's no
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* risk of corrupting data since the linker scripts won't mix code and
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* data.
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* On x86_64 you need the compiler flag:
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*
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* Modules built with -O3 and without the profiling flags might have
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* these same nop instructions, but that shouldn't be problematic since
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* they're only there for the puposes of aligning jumps, and therefore
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* aren't actually executed. However codebases that use huge function
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* alignments with wide-nop slides could pose minor issues. Further note
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* that Cosmopolitan sources are almost never intentionally written to
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* use code alignment, since we've only seen a few cases where it helps.
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* -fpatchable-function-entry=11,9
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*
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* On Aarch64 you need the compiler flag:
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*
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* -fpatchable-function-entry=7,6
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*
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* This function can currently only be called once.
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*
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* @param dest is the address of the target function, which all hookable
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* functions shall be reprogrammed to call from their epilogues; and
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* must be sufficiently close in memory to the the program image, in
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* order to meet ISA displacement requirements
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* @param st can be obtained using `GetSymbolTable()`
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* @see ape/ape.lds
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*/
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privileged noinstrument noasan int __hook(void *ifunc,
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struct SymbolTable *symbols) {
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int rc;
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size_t i;
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char *p, *pe;
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intptr_t addr;
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privileged noinstrument noasan int __hook(void *dest, struct SymbolTable *st) {
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long i;
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sigset_t mask;
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uint64_t code, mcode;
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intptr_t kMcount = (intptr_t)&mcount;
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intptr_t kProgramCodeStart = (intptr_t)_ereal;
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intptr_t kPrivilegedStart = (intptr_t)__privileged_addr;
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if (!symbols) return -1;
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code_t *p, *pe;
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intptr_t lowest;
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if (!st) return -1;
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__morph_begin(&mask);
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for (i = 0; i < symbols->count; ++i) {
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if (symbols->addr_base + symbols->symbols[i].x < kProgramCodeStart) {
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continue;
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}
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if (symbols->addr_base + symbols->symbols[i].y >= kPrivilegedStart) {
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break;
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}
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for (p = (char *)symbols->addr_base + symbols->symbols[i].x,
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pe = (char *)symbols->addr_base + symbols->symbols[i].y;
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p + 8 - 1 <= pe; ++p) {
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code = ((uint64_t)(255 & p[7]) << 070 | (uint64_t)(255 & p[6]) << 060 |
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(uint64_t)(255 & p[5]) << 050 | (uint64_t)(255 & p[4]) << 040 |
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(uint64_t)(255 & p[3]) << 030 | (uint64_t)(255 & p[2]) << 020 |
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(uint64_t)(255 & p[1]) << 010 | (uint64_t)(255 & p[0]) << 000);
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/*
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* Test for -mrecord-mcount (w/ -fpie or -fpic)
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*
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* nopw 0x00(%rax,%rax,1) ← morphed by package.com
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* call *mcount(%rip) ← linked w/o -static
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* addr32 call mcount ← relaxed w/ -static
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* addr32 call mcount ← relaxed w/ -static
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*
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* Note that gcc refuses to insert the six byte nop.
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*/
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if ((code & 0x0000FFFFFFFFFFFF) == 0x0000441F0F66 ||
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(code & 0x0000FFFFFFFFFFFF) ==
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((((kMcount - ((intptr_t)&p[2] + 4)) << 16) | 0xE867) &
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0x0000FFFFFFFFFFFF) ||
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(code & 0x0000FFFFFFFFFFFF) ==
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((((kMcount - ((intptr_t)&p[2] + 4)) << 16) | 0xFF15) &
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0x0000FFFFFFFFFFFF)) {
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p[0] = 0x67;
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p[1] = 0xE8;
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addr = (intptr_t)ifunc - ((intptr_t)&p[2] + 4);
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p[2] = (addr & 0x000000ff) >> 000;
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p[3] = (addr & 0x0000ff00) >> 010;
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p[4] = (addr & 0x00ff0000) >> 020;
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p[5] = (addr & 0xff000000) >> 030;
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break;
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}
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/*
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* Test for -mnop-mcount (w/ -fno-pie)
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*/
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mcode = code & 0x000000FFFFFFFFFF;
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if ((mcode == 0x00441F0F /* nopl 0x00(%eax,%eax,1) [canonical] */) ||
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(mcode == 0x00041F0F67 /* nopl (%eax,%eax,1) [older gcc] */)) {
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if (p[-1] != 0x66 /* nopw 0x0(%rax,%rax,1) [donotwant] */) {
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p[0] = 0xE8 /* call Jvds */;
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addr = (intptr_t)ifunc - ((intptr_t)&p[1] + 4);
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p[1] = (addr & 0x000000ff) >> 000;
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p[2] = (addr & 0x0000ff00) >> 010;
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p[3] = (addr & 0x00ff0000) >> 020;
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p[4] = (addr & 0xff000000) >> 030;
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}
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break;
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}
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lowest = MAX((intptr_t)__executable_start, (intptr_t)_ereal);
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for (i = 0; i < st->count; ++i) {
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if (st->symbols[i].x < 9) continue;
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if (st->addr_base + st->symbols[i].x < lowest) continue;
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if (st->addr_base + st->symbols[i].y >= (intptr_t)__privileged_addr) break;
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p = (code_t *)((char *)st->addr_base + st->symbols[i].x);
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pe = (code_t *)((char *)st->addr_base + st->symbols[i].y);
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if (pe - p < 2) continue;
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if (IsVirginFunction(p)) {
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// kprintf("hooking %t\n", p);
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HookFunction(p, dest);
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} else {
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// kprintf("can't hook %t at %lx\n", p, p);
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}
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}
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__morph_end(&mask);
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