drgn/libdrgn/arch_ppc64.c

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// (C) Copyright IBM Corp. 2020
// SPDX-License-Identifier: LGPL-2.1-or-later
#include <byteswap.h>
#include <elf.h>
#include <endian.h>
#include <string.h>
#include "drgn.h"
#include "error.h"
#include "platform.h" // IWYU pragma: associated
#include "program.h"
#include "register_state.h"
#include "arch_ppc64_defs.inc"
static const struct drgn_cfi_row default_dwarf_cfi_row_ppc64 = DRGN_CFI_ROW(
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(lr)),
[DRGN_REGISTER_NUMBER(r1)] = { DRGN_CFI_RULE_CFA_PLUS_OFFSET },
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r14)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r15)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r16)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r17)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r18)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r19)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r20)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r21)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r22)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r23)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r24)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r25)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r26)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r27)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r28)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r29)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r30)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(r31)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(cr2)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(cr3)),
DRGN_CFI_SAME_VALUE_INIT(DRGN_REGISTER_NUMBER(cr4)),
);
// Unwind using the stack frame back chain. Note that leaf functions may not
// allocate a stack frame, so this may skip the caller of a leaf function. I
// don't know of a good way around that.
static struct drgn_error *
fallback_unwind_ppc64(struct drgn_program *prog,
struct drgn_register_state *regs,
struct drgn_register_state **ret)
{
struct drgn_error *err;
struct optional_uint64 r1 = drgn_register_state_get_u64(prog, regs, r1);
if (!r1.has_value)
return &drgn_stop;
// The stack pointer (r1) points to the lowest address of the stack
// frame (the stack grows downwards from high addresses to low
// addresses), which contains the caller's stack pointer.
uint64_t unwound_r1;
err = drgn_program_read_u64(prog, r1.value, false, &unwound_r1);
uint64_t saved_lr;
if (!err) {
if (unwound_r1 <= r1.value) {
// The unwound stack pointer is either 0, indicating the
// first stack frame, or invalid.
return &drgn_stop;
}
// The return address (the saved lr) is stored 16 bytes into the
// caller's stack frame.
err = drgn_program_read_memory(prog, &saved_lr, unwound_r1 + 16,
sizeof(saved_lr), false);
}
if (err) {
if (err->code == DRGN_ERROR_FAULT) {
drgn_error_destroy(err);
err = &drgn_stop;
}
return err;
}
struct drgn_register_state *unwound =
drgn_register_state_create(r1, false);
if (!unwound)
return &drgn_enomem;
drgn_register_state_set_from_buffer(unwound, lr, &saved_lr);
drgn_register_state_set_from_u64(prog, unwound, r1, unwound_r1);
drgn_register_state_set_pc_from_register(prog, unwound, lr);
*ret = unwound;
drgn_register_state_set_cfa(prog, regs, unwound_r1);
return NULL;
}
static struct drgn_error *
get_initial_registers_from_struct_ppc64(struct drgn_program *prog,
const void *buf, size_t size,
bool linux_kernel_prstatus,
bool linux_kernel_switched_out,
struct drgn_register_state **ret)
{
if (size < 312) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"registers are truncated");
}
bool bswap = drgn_platform_bswap(&prog->platform);
struct drgn_register_state *regs =
drgn_register_state_create(cr7, true);
if (!regs)
return &drgn_enomem;
/*
* In most cases, nip (word 32) contains the program counter. But, the
* NT_PRSTATUS note in Linux kernel vmcores is odd, and the saved stack
* pointer (r1) is for the program counter in the link register (word
* 36).
*/
uint64_t pc;
memcpy(&pc, (uint64_t *)buf + (linux_kernel_prstatus ? 36 : 32),
sizeof(pc));
if (bswap)
pc = bswap_64(pc);
drgn_register_state_set_pc(prog, regs, pc);
// Switched out tasks in the Linux kernel only save r14-r31, nip, and
// ccr.
if (!linux_kernel_switched_out) {
if (!linux_kernel_prstatus) {
drgn_register_state_set_from_buffer(regs, lr,
(uint64_t *)buf + 36);
}
drgn_register_state_set_range_from_buffer(regs, r0, r13, buf);
}
drgn_register_state_set_range_from_buffer(regs, r14, r31,
(uint64_t *)buf + 14);
uint64_t ccr;
memcpy(&ccr, (uint64_t *)regs + 38, sizeof(ccr));
uint64_t cr[8];
if (bswap) {
for (int i = 0; i < 8; i += 2) {
cr[i] = ccr & (UINT64_C(0xf) << (36 + 4 * i));
cr[i + 1] = ccr & (UINT64_C(0xf) << (32 + 4 * i));
}
} else {
for (int i = 0; i < 8; i++)
cr[i] = ccr & (UINT64_C(0xf) << (28 - 4 * i));
}
drgn_register_state_set_range_from_buffer(regs, cr0, cr7, cr);
*ret = regs;
return NULL;
}
static struct drgn_error *
pt_regs_get_initial_registers_ppc64(const struct drgn_object *obj,
struct drgn_register_state **ret)
{
return get_initial_registers_from_struct_ppc64(drgn_object_program(obj),
drgn_object_buffer(obj),
drgn_object_size(obj),
false, false, ret);
}
static struct drgn_error *
prstatus_get_initial_registers_ppc64(struct drgn_program *prog,
const void *prstatus, size_t size,
struct drgn_register_state **ret)
{
if (size < 112) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"NT_PRSTATUS is truncated");
}
bool is_linux_kernel = prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL;
return get_initial_registers_from_struct_ppc64(prog,
(char *)prstatus + 112,
size - 112,
is_linux_kernel, false,
ret);
}
// The Linux kernel saves the callee-saved registers in a struct pt_regs on the
// thread's kernel stack. See _switch() in arch/powerpc/kernel/entry_64.S (as of
// Linux v5.19).
static struct drgn_error *
linux_kernel_get_initial_registers_ppc64(const struct drgn_object *task_obj,
struct drgn_register_state **ret)
{
struct drgn_error *err;
struct drgn_program *prog = drgn_object_program(task_obj);
struct drgn_object sp_obj;
drgn_object_init(&sp_obj, prog);
// The top of the stack is saved in task->thread.ksp.
err = drgn_object_member_dereference(&sp_obj, task_obj, "thread");
if (err)
goto out;
err = drgn_object_member(&sp_obj, &sp_obj, "ksp");
if (err)
goto out;
uint64_t ksp;
err = drgn_object_read_unsigned(&sp_obj, &ksp);
if (err)
goto out;
// The previous stack pointer is stored at the top of the stack.
uint64_t r1;
err = drgn_program_read_u64(prog, ksp, false, &r1);
if (err)
goto out;
// The struct pt_regs is stored above the previous stack pointer.
struct drgn_qualified_type pt_regs_type;
err = drgn_program_find_type(prog, "struct pt_regs", NULL,
&pt_regs_type);
if (err)
goto out;
uint64_t sizeof_pt_regs;
err = drgn_type_sizeof(pt_regs_type.type, &sizeof_pt_regs);
if (err)
goto out;
char buf[312];
err = drgn_program_read_memory(prog, buf, r1 - sizeof_pt_regs,
sizeof(buf), false);
if (err)
goto out;
err = get_initial_registers_from_struct_ppc64(prog, buf, sizeof(buf),
false, true, ret);
if (err)
goto out;
drgn_register_state_set_from_u64(prog, *ret, r1, r1);
err = NULL;
out:
drgn_object_deinit(&sp_obj);
return err;
}
static struct drgn_error *
apply_elf_reloc_ppc64(const struct drgn_relocating_section *relocating,
uint64_t r_offset, uint32_t r_type,
const int64_t *r_addend, uint64_t sym_value)
{
switch (r_type) {
case R_PPC64_NONE:
return NULL;
case R_PPC64_ADDR32:
return drgn_reloc_add32(relocating, r_offset, r_addend,
sym_value);
case R_PPC64_REL32:
return drgn_reloc_add32(relocating, r_offset, r_addend,
sym_value
- (relocating->addr + r_offset));
case R_PPC64_ADDR64:
return drgn_reloc_add64(relocating, r_offset, r_addend,
sym_value);
case R_PPC64_REL64:
return drgn_reloc_add64(relocating, r_offset, r_addend,
sym_value
- (relocating->addr + r_offset));
default:
return DRGN_UNKNOWN_RELOCATION_TYPE(r_type);
}
}
struct pt_level {
uint16_t bits;
uint16_t shift;
uint64_t entries;
};
struct pgtable_iterator_ppc64 {
struct pgtable_iterator it;
const struct pt_level *pt_levels;
};
static const struct pt_level pt_levels_radix_4k[] = {
{ .bits = 9, .shift = 12, .entries = 512 }, // PTE
{ .bits = 9, .shift = 21, .entries = 512 }, // PMD
{ .bits = 9, .shift = 30, .entries = 512 }, // PUD
{ .bits = 13, .shift = 39, .entries = 8192 }, // PGD
};
static const struct pt_level pt_levels_radix_64k[] = {
{ .bits = 5, .shift = 16, .entries = 32 }, // PTE
{ .bits = 9, .shift = 21, .entries = 512 }, // PMD
{ .bits = 9, .shift = 30, .entries = 512 }, // PUD
{ .bits = 13, .shift = 39, .entries = 8192 }, // PGD
};
static inline uint64_t
get_page_mask(struct pgtable_iterator_ppc64 *it, int level)
{
return (((UINT64_C(1) << 53) - 1)
& ~((UINT64_C(1) << it->pt_levels[level].shift) - 1));
}
static uint16_t
get_index(struct pgtable_iterator_ppc64 *it, uint64_t va, uint16_t level)
{
uint64_t mask = it->pt_levels[level - 1].entries - 1;
return (va >> it->pt_levels[level - 1].shift) & mask;
}
static struct drgn_error *
linux_kernel_pgtable_iterator_create_ppc64(struct drgn_program * prog,
struct pgtable_iterator **ret)
{
uint64_t mmu_features;
struct drgn_error *err = NULL;
const uint64_t page_shift = prog->vmcoreinfo.page_shift;
struct drgn_object book3s, cur_cpu_spec, mmu_features_obj;
struct pgtable_iterator_ppc64 *it = malloc(sizeof(*it));
if (!it)
return &drgn_enomem;
drgn_object_init(&book3s, prog);
drgn_object_init(&cur_cpu_spec, prog);
drgn_object_init(&mmu_features_obj, prog);
if (page_shift == 16) {
it->pt_levels = pt_levels_radix_64k;
} else if (page_shift == 12) {
it->pt_levels = pt_levels_radix_4k;
} else {
err = drgn_error_create(DRGN_ERROR_OTHER,
"Unknown page size.");
goto out;
}
// Only BOOK3S CPU family is supported, not BOOK3E.
err = drgn_program_find_object(prog, "interrupt_base_book3e", NULL,
DRGN_FIND_OBJECT_ANY, &book3s);
if (!err) {
err = drgn_error_create(DRGN_ERROR_OTHER,
"virtual address translation is not available for BOOK3E CPU family");
goto out;
}
if (err->code != DRGN_ERROR_LOOKUP)
goto out;
drgn_error_destroy(err);
// Identify the MMU type.
err = drgn_program_find_object(prog, "cur_cpu_spec", NULL,
DRGN_FIND_OBJECT_ANY, &cur_cpu_spec);
if (err)
goto out;
err = drgn_object_member_dereference(&mmu_features_obj, &cur_cpu_spec,
"mmu_features");
if (err)
goto out;
err = drgn_object_read_unsigned(&mmu_features_obj, &mmu_features);
if (err)
goto out;
if (!(mmu_features & 0x40)) {
err = drgn_error_create(DRGN_ERROR_OTHER,
"virtual address translation is only supported for Radix MMU");
goto out;
}
*ret = &it->it;
out:
drgn_object_deinit(&book3s);
drgn_object_deinit(&cur_cpu_spec);
drgn_object_deinit(&mmu_features_obj);
if (err)
free(it);
return err;
}
static void
linux_kernel_pgtable_iterator_destroy_ppc64(struct pgtable_iterator *_it)
{
struct pgtable_iterator_ppc64 *it =
container_of(_it, struct pgtable_iterator_ppc64, it);
free(it);
}
static void
linux_kernel_pgtable_iterator_init_ppc64(struct drgn_program *prog,
struct pgtable_iterator *_it)
{
return;
}
static struct drgn_error *
linux_kernel_pgtable_iterator_next_ppc64(struct drgn_program *prog,
struct pgtable_iterator *_it,
uint64_t *virt_addr_ret,
uint64_t *phys_addr_ret)
{
// Page table entry status bits since Linux kernel commits 849f86a630e9
// ("powerpc/mm/book3s-64: Move _PAGE_PRESENT to the most significant
// bit") and 84c957560a7a ("powerpc/mm/book3s-64: Move _PAGE_PTE to 2nd
// most significant bit") (in v4.6).
static const uint64_t PAGE_PRESENT = UINT64_C(1) << 63;
static const uint64_t PAGE_PTE = UINT64_C(1) << 62;
static const uint64_t PT_MASK = UINT64_C(0xc0000000000000ff);
static const uint16_t levels = 4;
struct drgn_error *err;
struct pgtable_iterator_ppc64 *it =
container_of(_it, struct pgtable_iterator_ppc64, it);
uint64_t virt_addr = it->it.virt_addr;
uint64_t entry;
for (uint16_t level = levels;; level--) {
uint64_t table;
bool table_physical;
if (level == levels) {
table = it->it.pgtable;
table_physical = false;
} else {
// PAGE_PTE bit represents huge page.
if (!(entry & PAGE_PRESENT) || (entry & PAGE_PTE) || level == 0) {
uint64_t mask = (UINT64_C(1) << it->pt_levels[level].shift) - 1;
*virt_addr_ret = virt_addr & ~mask;
if (entry & PAGE_PRESENT)
*phys_addr_ret = entry & get_page_mask(it, level);
else
*phys_addr_ret = UINT64_MAX;
it->it.virt_addr = (virt_addr | mask) + 1;
return NULL;
}
table = entry & ~PT_MASK;
table_physical = true;
}
uint64_t index = get_index(it, virt_addr, level);
err = drgn_program_read_memory(prog, &entry,
table + (8 * index), 8,
table_physical);
if (err)
return err;
// Page table entries are always big-endian, even on ppc64le.
entry = be64toh(entry);
}
}
const struct drgn_architecture_info arch_info_ppc64 = {
.name = "ppc64",
.arch = DRGN_ARCH_PPC64,
.default_flags = (DRGN_PLATFORM_IS_64_BIT |
DRGN_PLATFORM_IS_LITTLE_ENDIAN),
DRGN_ARCHITECTURE_REGISTERS,
.default_dwarf_cfi_row = &default_dwarf_cfi_row_ppc64,
.fallback_unwind = fallback_unwind_ppc64,
.pt_regs_get_initial_registers = pt_regs_get_initial_registers_ppc64,
.prstatus_get_initial_registers = prstatus_get_initial_registers_ppc64,
.linux_kernel_get_initial_registers =
linux_kernel_get_initial_registers_ppc64,
.apply_elf_reloc = apply_elf_reloc_ppc64,
.linux_kernel_pgtable_iterator_create =
linux_kernel_pgtable_iterator_create_ppc64,
.linux_kernel_pgtable_iterator_destroy =
linux_kernel_pgtable_iterator_destroy_ppc64,
.linux_kernel_pgtable_iterator_init =
linux_kernel_pgtable_iterator_init_ppc64,
.linux_kernel_pgtable_iterator_next =
linux_kernel_pgtable_iterator_next_ppc64,
};