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ARM32 MMU support #244

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ARM32 MMU support #244

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150 changes: 150 additions & 0 deletions libdrgn/arch_arm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include <elf.h>

#include "platform.h" // IWYU pragma: associated
#include "program.h"

/*
* The ABI specification can be found at:
Expand Down Expand Up @@ -31,10 +32,159 @@ apply_elf_reloc_arm(const struct drgn_relocating_section *relocating,
}
}

#define LEVEL1_NUM_ENTRIES 4096
#define LEVEL2_NUM_ENTRIES 256

struct pgtable_iterator_arm {
struct pgtable_iterator it;
uint16_t index1;
uint16_t index2;
uint32_t level1[LEVEL1_NUM_ENTRIES];
uint32_t level2[LEVEL2_NUM_ENTRIES];
};

static struct drgn_error *
linux_kernel_pgtable_iterator_create_arm(struct drgn_program *prog,
struct pgtable_iterator **ret)
{
struct pgtable_iterator_arm *it = malloc(sizeof(*it));
if (!it)
return &drgn_enomem;
*ret = &it->it;
return NULL;
}

static void linux_kernel_pgtable_iterator_destroy_arm(struct pgtable_iterator *_it)
{
free(container_of(_it, struct pgtable_iterator_arm, it));
}

static void linux_kernel_pgtable_iterator_init_arm(struct drgn_program *prog,
struct pgtable_iterator *_it)
{
struct pgtable_iterator_arm *it =
container_of(_it, struct pgtable_iterator_arm, it);
it->index1 = 0xffff;
it->index2 = 0xffff;
}

static struct drgn_error *
mmu_mapped_entry(struct pgtable_iterator *_it, uint32_t entry, uint32_t mask,
uint64_t *virt_addr_ret, uint64_t *phys_addr_ret)
{
*virt_addr_ret = _it->virt_addr & ~mask;
*phys_addr_ret = entry & ~mask;
_it->virt_addr = (_it->virt_addr | mask) + 1;
return NULL;
}

static struct drgn_error *
mmu_unmapped_entry(struct pgtable_iterator *_it, uint32_t mask,
uint64_t *virt_addr_ret, uint64_t *phys_addr_ret)
{
*virt_addr_ret = _it->virt_addr & ~mask;
*phys_addr_ret = UINT64_MAX;
_it->virt_addr = (_it->virt_addr | mask) + 1;
return NULL;
}

static struct drgn_error *
mmu_read_table(struct drgn_program *prog, uint32_t *level, uint32_t table,
uint16_t index, uint32_t num_entries, bool physical)
{
return drgn_program_read_memory(prog, &level[index], table + 4 * index,
4 * (num_entries - index), physical);
}

static struct drgn_error *
linux_kernel_pgtable_iterator_next_arm(struct drgn_program *prog,
struct pgtable_iterator *_it,
uint64_t *virt_addr_ret,
uint64_t *phys_addr_ret)
{
struct drgn_error *err;
const bool bswap = drgn_platform_bswap(&prog->platform);
struct pgtable_iterator_arm *it =
container_of(_it, struct pgtable_iterator_arm, it);
const uint64_t virt_addr = it->it.virt_addr;

uint16_t index;
uint32_t table;
uint32_t entry;

if (it->index2 >= LEVEL2_NUM_ENTRIES) {
if (it->index1 >= LEVEL1_NUM_ENTRIES) {
// Refill level1 table
table = it->it.pgtable;
index = (virt_addr >> 20) & 0xfff;
err = mmu_read_table(prog, it->level1, table, index,
LEVEL1_NUM_ENTRIES, false);
if (err)
return err;
it->index1 = index;
}

// MMU level 1
entry = it->level1[it->index1++];
if (bswap)
entry = bswap_32(entry);

if ((entry & 0x3) == 0) {
// Fault
return mmu_unmapped_entry(_it, 0x000fffff,
virt_addr_ret, phys_addr_ret);
} else if (((entry & 0x3) == 2) && ((entry & 0x40000) == 0)) {
// Section
return mmu_mapped_entry(_it, entry, 0x000fffff,
virt_addr_ret, phys_addr_ret);
} else if ((entry & 0x3) == 1) {
// Pointer to 2nd level
// Refill level2 table
table = entry & 0xfffffc00;
index = (virt_addr >> 12) & 0xff;
err = mmu_read_table(prog, it->level2, table, index,
LEVEL2_NUM_ENTRIES, true);
if (err)
return err;

it->index2 = index;
} else {
return drgn_error_format(DRGN_ERROR_OTHER,
"unsupported ARM level 1 entry: 0x%08x", entry);
}
}

// MMU level 2
entry = it->level2[it->index2++];
if (bswap)
entry = bswap_32(entry);

if ((entry & 0x3) == 0) {
// Fault
return mmu_unmapped_entry(_it, 0x00000fff,
virt_addr_ret, phys_addr_ret);
} else if ((entry & 0x2) == 2) {
// Small page
return mmu_mapped_entry(_it, entry, 0x00000fff,
virt_addr_ret, phys_addr_ret);
} else {
return drgn_error_format(DRGN_ERROR_OTHER,
"unsupported ARM level 2 entry: 0x%08x", entry);
}
}

const struct drgn_architecture_info arch_info_arm = {
.name = "Arm",
.arch = DRGN_ARCH_ARM,
.default_flags = DRGN_PLATFORM_IS_LITTLE_ENDIAN,
.register_by_name = drgn_register_by_name_unknown,
.apply_elf_reloc = apply_elf_reloc_arm,
.linux_kernel_pgtable_iterator_create =
linux_kernel_pgtable_iterator_create_arm,
.linux_kernel_pgtable_iterator_destroy =
linux_kernel_pgtable_iterator_destroy_arm,
.linux_kernel_pgtable_iterator_init =
linux_kernel_pgtable_iterator_init_arm,
.linux_kernel_pgtable_iterator_next =
linux_kernel_pgtable_iterator_next_arm,
};