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fix(bpf,modern_bpf): better 32bit support preadv/pwritev family
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Signed-off-by: Roberto Scolaro <[email protected]>
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@therealbobo
therealbobo committed May 2, 2024
1 parent 6435dbd commit e9d657d
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Showing 3 changed files with 193 additions and 9 deletions.
135 changes: 135 additions & 0 deletions driver/bpf/fillers.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -571,6 +571,111 @@ FILLER(sys_poll_x, true)

#define MAX_IOVCNT 32

static __always_inline int bpf_parse_readv_writev_bufs_ia32(struct filler_data *data,
const struct compat_iovec __user *iovsrc,
unsigned long iovcnt,
long retval,
int flags)
{
const struct compat_iovec *iov;
int res = PPM_SUCCESS;
unsigned int copylen;
long size = 0;
int j;

copylen = iovcnt * sizeof(struct compat_iovec);
iov = (const struct compat_iovec *)data->tmp_scratch;

if (copylen > SCRATCH_SIZE_MAX)
{
return PPM_FAILURE_FRAME_SCRATCH_MAP_FULL;
}

#ifdef BPF_FORBIDS_ZERO_ACCESS
if (copylen)
if (bpf_probe_read_user((void *)iov,
((copylen - 1) & SCRATCH_SIZE_MAX) + 1,
(void *)iovsrc))
#else
if (bpf_probe_read_user((void *)iov,
copylen & SCRATCH_SIZE_MAX,
(void *)iovsrc))
#endif
return PPM_FAILURE_INVALID_USER_MEMORY;


#pragma unroll
for (j = 0; j < MAX_IOVCNT; ++j) {
if (j == iovcnt)
break;
// BPF seems to require a hard limit to avoid overflows
if (size == LONG_MAX)
break;

size += iov[j].iov_len;
}

if ((flags & PRB_FLAG_IS_WRITE) == 0)
if (size > retval)
size = retval;

if (flags & PRB_FLAG_PUSH_SIZE) {
res = bpf_push_u32_to_ring(data, (uint32_t)size);
CHECK_RES(res);
}

if (flags & PRB_FLAG_PUSH_DATA) {
if (size > 0) {
unsigned long off = _READ(data->state->tail_ctx.curoff);
unsigned long remaining = size;
int j;

#pragma unroll
for (j = 0; j < MAX_IOVCNT; ++j) {
volatile unsigned int to_read;

if (j == iovcnt)
break;

unsigned long off_bounded = off & SCRATCH_SIZE_HALF;
if (off > SCRATCH_SIZE_HALF)
break;

if (iov[j].iov_len <= remaining)
to_read = iov[j].iov_len;
else
to_read = remaining;

if (to_read > SCRATCH_SIZE_HALF)
to_read = SCRATCH_SIZE_HALF;

#ifdef BPF_FORBIDS_ZERO_ACCESS
if (to_read)
if (bpf_probe_read_user(&data->buf[off_bounded],
((to_read - 1) & SCRATCH_SIZE_HALF) + 1,
iov[j].iov_base))
#else
if (bpf_probe_read_user(&data->buf[off_bounded],
to_read & SCRATCH_SIZE_HALF,
iov[j].iov_base))
#endif
return PPM_FAILURE_INVALID_USER_MEMORY;

remaining -= to_read;
off += to_read;
}
} else {
size = 0;
}

data->fd = bpf_syscall_get_argument(data, 0);
data->curarg_already_on_frame = true;
return __bpf_val_to_ring(data, 0, size, PT_BYTEBUF, -1, true, KERNEL);
}

return res;
}

static __always_inline int bpf_parse_readv_writev_bufs(struct filler_data *data,
const struct iovec __user *iovsrc,
unsigned long iovcnt,
Expand Down Expand Up @@ -789,11 +894,26 @@ FILLER(sys_writev_pwritev_x, true)
*/
val = bpf_syscall_get_argument(data, 1);
iovcnt = bpf_syscall_get_argument(data, 2);
#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
if (!bpf_in_ia32_syscall())
#endif
{
res = bpf_parse_readv_writev_bufs(data,
(const struct iovec __user *)val,
iovcnt,
0,
PRB_FLAG_PUSH_DATA | PRB_FLAG_IS_WRITE);
}
#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
else
{
res = bpf_parse_readv_writev_bufs_ia32(data,
(const struct compat_iovec __user *)val,
iovcnt,
0,
PRB_FLAG_PUSH_DATA | PRB_FLAG_IS_WRITE);
}
#endif

/* if there was an error we send an empty param.
* we can improve this in the future but at least we don't lose the whole event.
Expand Down Expand Up @@ -4002,11 +4122,26 @@ FILLER(sys_pwritev_e, true)
unsigned long iov_cnt = bpf_syscall_get_argument(data, 2);

/* Parameter 2: size (type: PT_UINT32) */
#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
if (!bpf_in_ia32_syscall())
#endif
{
res = bpf_parse_readv_writev_bufs(data,
(const struct iovec __user *)iov_pointer,
iov_cnt,
0,
PRB_FLAG_PUSH_SIZE | PRB_FLAG_IS_WRITE);
}
#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
else
{
res = bpf_parse_readv_writev_bufs_ia32(data,
(const struct compat_iovec __user *)iov_pointer,
iov_cnt,
0,
PRB_FLAG_PUSH_SIZE | PRB_FLAG_IS_WRITE);
}
#endif

/* if there was an error we send a size equal to `0`.
* we can improve this in the future but at least we don't lose the whole event.
Expand Down
31 changes: 28 additions & 3 deletions driver/modern_bpf/helpers/store/auxmap_store_params.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1010,7 +1010,15 @@ static __always_inline void auxmap__store_iovec_size_param(struct auxiliary_map
static __always_inline void auxmap__store_iovec_data_param(struct auxiliary_map *auxmap, unsigned long iov_pointer, unsigned long iov_cnt, unsigned long len_to_read)
{
/* We use the second part of our auxmap as a scratch space. */
uint32_t total_iovec_size = iov_cnt * bpf_core_type_size(struct iovec);
uint32_t total_iovec_size = 0;
if(!bpf_in_ia32_syscall())
{
total_iovec_size = iov_cnt * bpf_core_type_size(struct iovec);
}
else
{
total_iovec_size = iov_cnt * bpf_core_type_size(struct compat_iovec);
}
if(bpf_probe_read_user((void *)&auxmap->data[MAX_PARAM_SIZE],
SAFE_ACCESS(total_iovec_size),
(void *)iov_pointer))
Expand All @@ -1023,7 +1031,16 @@ static __always_inline void auxmap__store_iovec_data_param(struct auxiliary_map
uint32_t total_size_to_read = 0;

/* Pointer to iovec structs */
const struct iovec *iovec = (const struct iovec *)&auxmap->data[MAX_PARAM_SIZE];
const struct iovec *iovec;
const struct compat_iovec *compat_iovec;
if(!bpf_in_ia32_syscall())
{
iovec = (const struct iovec *)&auxmap->data[MAX_PARAM_SIZE];
}
else
{
compat_iovec = (const struct compat_iovec *)&auxmap->data[MAX_PARAM_SIZE];
}
uint64_t initial_payload_pos = auxmap->payload_pos;
for(int j = 0; j < MAX_IOVCNT; j++)
{
Expand All @@ -1041,7 +1058,15 @@ static __always_inline void auxmap__store_iovec_data_param(struct auxiliary_map
break;
}

uint16_t bytes_read = push__bytebuf(auxmap->data, &auxmap->payload_pos, (unsigned long)iovec[j].iov_base, iovec[j].iov_len, USER);
uint16_t bytes_read;
if(!bpf_in_ia32_syscall())
{
bytes_read = push__bytebuf(auxmap->data, &auxmap->payload_pos, (unsigned long)iovec[j].iov_base, iovec[j].iov_len, USER);
}
else
{
bytes_read = push__bytebuf(auxmap->data, &auxmap->payload_pos, (unsigned long)compat_iovec[j].iov_base, compat_iovec[j].iov_len, USER);
}
if(!bytes_read)
{
push__param_len(auxmap->data, &auxmap->lengths_pos, total_size_to_read);
Expand Down
36 changes: 30 additions & 6 deletions driver/modern_bpf/helpers/store/ringbuf_store_params.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,16 @@ static __always_inline void ringbuf__store_iovec_size_param(struct ringbuf_struc
return;
}

uint32_t total_iovec_size = iov_cnt * bpf_core_type_size(struct iovec);
uint32_t total_iovec_size = 0;
if(!bpf_in_ia32_syscall())
{
total_iovec_size = iov_cnt * bpf_core_type_size(struct iovec);
}
else
{
total_iovec_size = iov_cnt * bpf_core_type_size(struct compat_iovec);
}

if(bpf_probe_read_user((void *)&auxmap->data[0],
SAFE_ACCESS(total_iovec_size),
(void *)iov_pointer))
Expand All @@ -320,14 +329,29 @@ static __always_inline void ringbuf__store_iovec_size_param(struct ringbuf_struc
uint32_t total_size_to_read = 0;

/* Pointer to iovec structs */
const struct iovec *iovec = (const struct iovec *)&auxmap->data[0];
for(int j = 0; j < MAX_IOVCNT; j++)
if(!bpf_in_ia32_syscall())
{
const struct iovec *iovec = (const struct iovec *)&auxmap->data[0];
for(int j = 0; j < MAX_IOVCNT; j++)
{
if(j == iov_cnt)
{
break;
}
total_size_to_read += iovec[j].iov_len;
}
}
else
{
if(j == iov_cnt)
const struct compat_iovec *iovec = (const struct compat_iovec *)&auxmap->data[0];
for(int j = 0; j < MAX_IOVCNT; j++)
{
break;
if(j == iov_cnt)
{
break;
}
total_size_to_read += iovec[j].iov_len;
}
total_size_to_read += iovec[j].iov_len;
}
ringbuf__store_u32(ringbuf, total_size_to_read);
}

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