mirror of
https://github.com/JakeHillion/drgn.git
synced 2024-12-23 01:33:06 +00:00
1b47b866b4
Commit eea5422546 ("libdrgn: make Linux kernel stack unwinding more
robust") overlooked that if the task is running in userspace, the stack
pointer in PRSTATUS obviously won't match the kernel stack pointer.
Let's bite the bullet and use the PID. If the race shows up in practice,
we can try to come up with another workaround.
549 lines
13 KiB
C
549 lines
13 KiB
C
%{
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// Copyright (c) Facebook, Inc. and its affiliates.
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// SPDX-License-Identifier: GPL-3.0+
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#include <byteswap.h>
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#include "internal.h"
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#include "linux_kernel.h"
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#include "platform.h"
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#include "program.h"
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%}
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x86-64
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%%
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rax
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rdx
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rcx
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rbx
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rsi
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rdi
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rbp
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rsp
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r8
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r9
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r10
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r11
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r12
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r13
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r14
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r15
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# The System V ABI calls this the return address (RA) register, but it's
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# effectively the instruction pointer.
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rip
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xmm0
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xmm1
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xmm2
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xmm3
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xmm4
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xmm5
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xmm6
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xmm7
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xmm8
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xmm9
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xmm10
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xmm11
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xmm12
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xmm13
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xmm14
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xmm15
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st0
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st1
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st2
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st3
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st4
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st5
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st6
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st7
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mm0
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mm1
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mm2
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mm3
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mm4
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mm5
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mm6
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mm7
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rFLAGS
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es
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cs
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ss
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ds
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fs
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gs
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fs.base, 58
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gs.base
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tr, 62
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ldtr
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mxcsr
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fcw
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fsw
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xmm16
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xmm17
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xmm18
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xmm19
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xmm20
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xmm21
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xmm22
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xmm23
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xmm24
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xmm25
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xmm26
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xmm27
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xmm28
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xmm29
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xmm30
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xmm31
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k0, 118
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k1
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k2
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k3
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k4
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k5
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k6
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k7
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bnd0
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bnd1
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bnd2
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bnd3
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%%
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/*
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* The in-kernel struct pt_regs, UAPI struct pt_regs, elf_gregset_t, and struct
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* user_regs_struct all have the same layout.
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*/
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static struct drgn_error *
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set_initial_registers_from_struct_x86_64(Dwfl_Thread *thread, const void *regs,
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size_t size, bool bswap)
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{
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Dwarf_Word dwarf_regs[17];
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if (size < 160) {
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return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
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"registers are truncated");
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}
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#define READ_REGISTER(n) ({ \
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uint64_t reg; \
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memcpy(®, (uint64_t *)regs + n, sizeof(reg)); \
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bswap ? bswap_64(reg) : reg; \
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})
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dwarf_regs[0] = READ_REGISTER(10); /* rax */
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dwarf_regs[1] = READ_REGISTER(12); /* rdx */
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dwarf_regs[2] = READ_REGISTER(11); /* rcx */
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dwarf_regs[3] = READ_REGISTER(5); /* rbx */
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dwarf_regs[4] = READ_REGISTER(13); /* rsi */
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dwarf_regs[5] = READ_REGISTER(14); /* rdi */
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dwarf_regs[6] = READ_REGISTER(4); /* rbp */
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dwarf_regs[7] = READ_REGISTER(19); /* rsp */
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dwarf_regs[8] = READ_REGISTER(9); /* r8 */
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dwarf_regs[9] = READ_REGISTER(8); /* r9 */
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dwarf_regs[10] = READ_REGISTER(7); /* r10 */
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dwarf_regs[11] = READ_REGISTER(6); /* r11 */
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dwarf_regs[12] = READ_REGISTER(3); /* r12 */
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dwarf_regs[13] = READ_REGISTER(2); /* r13 */
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dwarf_regs[14] = READ_REGISTER(1); /* r14 */
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dwarf_regs[15] = READ_REGISTER(0); /* r15 */
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dwarf_regs[16] = READ_REGISTER(16); /* rip */
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#undef READ_REGISTER
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if (!dwfl_thread_state_registers(thread, 0, 17, dwarf_regs))
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return drgn_error_libdwfl();
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return NULL;
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}
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static struct drgn_error *
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pt_regs_set_initial_registers_x86_64(Dwfl_Thread *thread,
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const struct drgn_object *obj)
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{
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bool bswap = (obj->value.little_endian !=
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(__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__));
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return set_initial_registers_from_struct_x86_64(thread,
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drgn_object_buffer(obj),
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drgn_buffer_object_size(obj),
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bswap);
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}
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static struct drgn_error *
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prstatus_set_initial_registers_x86_64(struct drgn_program *prog,
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Dwfl_Thread *thread, const void *prstatus,
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size_t size)
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{
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if (size < 112) {
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return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
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"NT_PRSTATUS is truncated");
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}
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return set_initial_registers_from_struct_x86_64(thread,
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(char *)prstatus + 112,
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size - 112,
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drgn_program_bswap(prog));
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}
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static inline struct drgn_error *read_register(struct drgn_object *reg_obj,
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struct drgn_object *frame_obj,
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const char *name,
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Dwarf_Addr *ret)
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{
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struct drgn_error *err;
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uint64_t reg;
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err = drgn_object_member_dereference(reg_obj, frame_obj, name);
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if (err)
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return err;
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err = drgn_object_read_unsigned(reg_obj, ®);
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if (err)
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return err;
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*ret = reg;
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return NULL;
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}
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static struct drgn_error *
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set_initial_registers_inactive_task_frame(Dwfl_Thread *thread,
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struct drgn_object *frame_obj)
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{
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struct drgn_error *err;
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struct drgn_object reg_obj;
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Dwarf_Word dwarf_regs[5];
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uint64_t sp;
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drgn_object_init(®_obj, frame_obj->prog);
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err = read_register(®_obj, frame_obj, "bx", &dwarf_regs[0]);
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if (err)
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goto out;
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/* rbx is register 3. */
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if (!dwfl_thread_state_registers(thread, 3, 1, dwarf_regs)) {
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err = drgn_error_libdwfl();
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goto out;
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}
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err = read_register(®_obj, frame_obj, "bp", &dwarf_regs[0]);
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if (err)
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goto out;
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err = drgn_object_read_unsigned(frame_obj, &sp);
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if (err)
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goto out;
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/* rbp is register 6. */
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if (!dwfl_thread_state_registers(thread, 6, 1, dwarf_regs)) {
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err = drgn_error_libdwfl();
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goto out;
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}
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err = read_register(®_obj, frame_obj, "r12", &dwarf_regs[0]);
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if (err)
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goto out;
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err = read_register(®_obj, frame_obj, "r13", &dwarf_regs[1]);
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if (err)
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goto out;
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err = read_register(®_obj, frame_obj, "r14", &dwarf_regs[2]);
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if (err)
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goto out;
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err = read_register(®_obj, frame_obj, "r15", &dwarf_regs[3]);
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if (err)
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goto out;
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err = read_register(®_obj, frame_obj, "ret_addr", &dwarf_regs[4]);
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if (err)
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goto out;
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/* r12-r15 are registers 12-15; register 16 is the return address. */
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if (!dwfl_thread_state_registers(thread, 12, 5, dwarf_regs)) {
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err = drgn_error_libdwfl();
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goto out;
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}
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err = NULL;
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out:
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drgn_object_deinit(®_obj);
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return err;
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}
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static struct drgn_error *
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linux_kernel_set_initial_registers_x86_64(Dwfl_Thread *thread,
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const struct drgn_object *task_obj)
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{
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struct drgn_error *err;
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struct drgn_program *prog = task_obj->prog;
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struct drgn_object sp_obj;
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drgn_object_init(&sp_obj, prog);
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err = drgn_object_member_dereference(&sp_obj, task_obj, "thread");
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if (err)
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goto out;
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err = drgn_object_member(&sp_obj, &sp_obj, "sp");
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if (err)
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goto out;
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uint64_t sp;
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err = drgn_object_read_unsigned(&sp_obj, &sp);
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if (err)
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goto out;
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Dwarf_Word dwarf_reg = sp;
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/* rsp is register 7. */
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if (!dwfl_thread_state_registers(thread, 7, 1, &dwarf_reg)) {
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err = drgn_error_libdwfl();
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goto out;
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}
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/*
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* Since Linux kernel commit 0100301bfdf5 ("sched/x86: Rewrite the
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* switch_to() code") (in v4.9), sp points to a struct
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* inactive_task_frame, which we can use to get most registers. Before
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* that, it points to bp.
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*/
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struct drgn_qualified_type frame_type;
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err = drgn_program_find_type(prog, "struct inactive_task_frame *", NULL,
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&frame_type);
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if (!err) {
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err = drgn_object_cast(&sp_obj, frame_type, &sp_obj);
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if (err)
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goto out;
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err = set_initial_registers_inactive_task_frame(thread,
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&sp_obj);
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} else if (err->code == DRGN_ERROR_LOOKUP) {
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uint64_t bp;
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drgn_error_destroy(err);
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err = drgn_program_find_type(prog, "unsigned long", NULL,
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&frame_type);
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if (err)
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goto out;
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err = drgn_object_set_reference(&sp_obj, frame_type, sp, 0, 0,
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DRGN_PROGRAM_ENDIAN);
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if (err)
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goto out;
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err = drgn_object_read_unsigned(&sp_obj, &bp);
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if (err)
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goto out;
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dwarf_reg = bp;
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/* rbp is register 6. */
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if (!dwfl_thread_state_registers(thread, 6, 1, &dwarf_reg)) {
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err = drgn_error_libdwfl();
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goto out;
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}
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err = NULL;
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}
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out:
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drgn_object_deinit(&sp_obj);
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return err;
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}
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static struct drgn_error *
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linux_kernel_get_page_offset_x86_64(struct drgn_program *prog, uint64_t *ret)
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{
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struct drgn_error *err;
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struct drgn_object obj;
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uint64_t pgd;
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/*
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* If KASLR is enabled, PAGE_OFFSET is easily available via
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* page_offset_base.
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*/
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drgn_object_init(&obj, prog);
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err = drgn_program_find_object(prog, "page_offset_base", NULL,
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DRGN_FIND_OBJECT_VARIABLE, &obj);
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if (!err) {
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err = drgn_object_read_unsigned(&obj, ret);
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goto out;
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}
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if (err->code == DRGN_ERROR_LOOKUP)
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drgn_error_destroy(err);
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else
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goto out;
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/*
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* If not, we determine it based on the kernel page table. Before Linux
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* kernel commit d52888aa2753 ("x86/mm: Move LDT remap out of KASLR
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* region on 5-level paging") (in v4.20), PAGE_OFFSET was pgd slot 272.
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* After that, it is pgd slot 273, and slot 272 is empty (reserved for
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* Local Descriptor Table mappings for userspace tasks).
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*/
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err = drgn_program_read_u64(prog,
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prog->vmcoreinfo.swapper_pg_dir + 272 * 8,
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false, &pgd);
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if (err)
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goto out;
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if (pgd) {
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if (prog->vmcoreinfo.pgtable_l5_enabled)
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*ret = UINT64_C(0xff10000000000000);
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else
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*ret = UINT64_C(0xffff880000000000);
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} else {
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if (prog->vmcoreinfo.pgtable_l5_enabled)
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*ret = UINT64_C(0xff11000000000000);
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else
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*ret = UINT64_C(0xffff888000000000);
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}
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out:
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drgn_object_deinit(&obj);
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return err;
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}
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static struct drgn_error *
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linux_kernel_get_vmemmap_x86_64(struct drgn_program *prog, uint64_t *ret)
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{
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struct drgn_error *err;
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struct drgn_object obj;
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/* If KASLR is enabled, vmemmap is vmemmap_base. */
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drgn_object_init(&obj, prog);
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err = drgn_program_find_object(prog, "vmemmap_base", NULL,
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DRGN_FIND_OBJECT_VARIABLE, &obj);
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if (!err) {
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err = drgn_object_read_unsigned(&obj, ret);
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goto out;
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}
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if (err->code == DRGN_ERROR_LOOKUP) {
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drgn_error_destroy(err);
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err = NULL;
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} else {
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goto out;
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}
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/* Otherwise, it depends on whether we have 5-level page tables. */
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if (prog->vmcoreinfo.pgtable_l5_enabled)
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*ret = UINT64_C(0xffd4000000000000);
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else
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*ret = UINT64_C(0xffffea0000000000);
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out:
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drgn_object_deinit(&obj);
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return err;
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}
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static struct drgn_error *
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linux_kernel_live_direct_mapping_fallback_x86_64(struct drgn_program *prog,
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uint64_t *address_ret,
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uint64_t *size_ret)
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{
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struct drgn_error *err;
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unsigned long page_offset_base_address;
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*size_ret = UINT64_C(1) << 46;
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err = proc_kallsyms_symbol_addr("page_offset_base",
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&page_offset_base_address);
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if (!err) {
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return drgn_program_read_word(prog, page_offset_base_address,
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false, address_ret);
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} else if (err == &drgn_not_found) {
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/*
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* This is only called for pre-4.11 kernels, so we can assume
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* the old location.
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*/
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*address_ret = UINT64_C(0xffff880000000000);
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return NULL;
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} else {
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return err;
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}
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}
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struct pgtable_iterator_x86_64 {
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uint16_t index[5];
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uint64_t table[5][512];
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};
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static void pgtable_iterator_arch_init_x86_64(void *buf)
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{
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struct pgtable_iterator_x86_64 *arch = buf;
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memset(arch->index, 0xff, sizeof(arch->index));
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memset(arch->table, 0, sizeof(arch->table));
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}
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static struct drgn_error *
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linux_kernel_pgtable_iterator_next_x86_64(struct pgtable_iterator *it,
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uint64_t *virt_addr_ret,
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uint64_t *phys_addr_ret)
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{
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static const int PAGE_SHIFT = 12;
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static const int PGTABLE_SHIFT = 9;
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static const int PGTABLE_MASK = (1 << PGTABLE_SHIFT) - 1;
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static const uint64_t PRESENT = 0x1;
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static const uint64_t PSE = 0x80; /* a.k.a. huge page */
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static const uint64_t ADDRESS_MASK = UINT64_C(0xffffffffff000);
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struct drgn_program *prog = it->prog;
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struct pgtable_iterator_x86_64 *arch = (void *)it->arch;
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struct drgn_error *err;
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bool bswap = drgn_program_bswap(prog);
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int levels = prog->vmcoreinfo.pgtable_l5_enabled ? 5 : 4, level;
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/* Find the lowest level with cached entries. */
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for (level = 0; level < levels; level++) {
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if (arch->index[level] < ARRAY_SIZE(arch->table[level]))
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break;
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}
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/* For every level below that, refill the cache/return pages. */
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for (;; level--) {
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uint64_t table;
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bool table_physical;
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uint16_t index;
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if (level == levels) {
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uint64_t start_non_canonical, end_non_canonical;
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start_non_canonical = (UINT64_C(1) <<
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(PAGE_SHIFT +
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PGTABLE_SHIFT * levels - 1));
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end_non_canonical = (UINT64_MAX <<
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(PAGE_SHIFT +
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PGTABLE_SHIFT * levels - 1));
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if (it->virt_addr >= start_non_canonical &&
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it->virt_addr < end_non_canonical) {
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*virt_addr_ret = start_non_canonical;
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*phys_addr_ret = UINT64_MAX;
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it->virt_addr = end_non_canonical;
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return NULL;
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}
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table = it->pgtable;
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table_physical = false;
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} else {
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uint64_t entry = arch->table[level][arch->index[level]++];
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if (bswap)
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entry = bswap_64(entry);
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table = entry & ADDRESS_MASK;
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if (!(entry & PRESENT) || (entry & PSE) || level == 0) {
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uint64_t mask = (UINT64_C(1) <<
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(PAGE_SHIFT +
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PGTABLE_SHIFT * level)) - 1;
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*virt_addr_ret = it->virt_addr & ~mask;
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if (entry & PRESENT)
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*phys_addr_ret = table & ~mask;
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else
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*phys_addr_ret = UINT64_MAX;
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it->virt_addr = (it->virt_addr | mask) + 1;
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return NULL;
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}
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table_physical = true;
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}
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|
index = (it->virt_addr >>
|
|
(PAGE_SHIFT + PGTABLE_SHIFT * (level - 1))) & PGTABLE_MASK;
|
|
/*
|
|
* It's only marginally more expensive to read 4096 bytes than 8
|
|
* bytes, so we always read to the end of the table.
|
|
*/
|
|
err = drgn_program_read_memory(prog,
|
|
&arch->table[level - 1][index],
|
|
table + 8 * index,
|
|
sizeof(arch->table[0]) - 8 * index,
|
|
table_physical);
|
|
if (err)
|
|
return err;
|
|
arch->index[level - 1] = index;
|
|
}
|
|
}
|
|
|
|
const struct drgn_architecture_info arch_info_x86_64 = {
|
|
ARCHITECTURE_INFO,
|
|
.default_flags = (DRGN_PLATFORM_IS_64_BIT |
|
|
DRGN_PLATFORM_IS_LITTLE_ENDIAN),
|
|
.pt_regs_set_initial_registers = pt_regs_set_initial_registers_x86_64,
|
|
.prstatus_set_initial_registers = prstatus_set_initial_registers_x86_64,
|
|
.linux_kernel_set_initial_registers =
|
|
linux_kernel_set_initial_registers_x86_64,
|
|
.linux_kernel_get_page_offset = linux_kernel_get_page_offset_x86_64,
|
|
.linux_kernel_get_vmemmap = linux_kernel_get_vmemmap_x86_64,
|
|
.linux_kernel_live_direct_mapping_fallback =
|
|
linux_kernel_live_direct_mapping_fallback_x86_64,
|
|
.pgtable_iterator_arch_size = sizeof(struct pgtable_iterator_x86_64),
|
|
.pgtable_iterator_arch_init = pgtable_iterator_arch_init_x86_64,
|
|
.linux_kernel_pgtable_iterator_next =
|
|
linux_kernel_pgtable_iterator_next_x86_64,
|
|
};
|