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Merge branch 'Add USDT support for s390'

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Ilya Leoshkevich says:

====================

This series adds USDT support for s390, making the "usdt" test pass
there. Patch 1 is a collection of minor cleanups, patch 2 adds
BPF-side support, patch 3 adds userspace-side support.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
This commit is contained in:
Andrii Nakryiko 2022-04-07 20:59:12 -07:00
commit 700a6ef1fa
2 changed files with 66 additions and 8 deletions
tools/lib/bpf
usdt.bpf.husdt.c

7
tools/lib/bpf/usdt.bpf.h
View File

@ -166,7 +166,7 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
case BPF_USDT_ARG_REG_DEREF:
/* Arg is in memory addressed by register, plus some offset
* (e.g., "-4@-1204(%rbp)" in USDT arg spec). Register is
* identified lik with BPF_USDT_ARG_REG case, and the offset
* identified like with BPF_USDT_ARG_REG case, and the offset
* is in arg_spec->val_off. We first fetch register contents
* from pt_regs, then do another user-space probe read to
* fetch argument value itself.
@ -177,6 +177,9 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
err = bpf_probe_read_user(&val, sizeof(val), (void *)val + arg_spec->val_off);
if (err)
return err;
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
val >>= arg_spec->arg_bitshift;
#endif
break;
default:
return -EINVAL;
@ -198,7 +201,7 @@ int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res)
/* Retrieve user-specified cookie value provided during attach as
* bpf_usdt_opts.usdt_cookie. This serves the same purpose as BPF cookie
* returned by bpf_get_attach_cookie(). Libbpf's support for USDT is itself
* utilizaing BPF cookies internally, so user can't use BPF cookie directly
* utilizing BPF cookies internally, so user can't use BPF cookie directly
* for USDT programs and has to use bpf_usdt_cookie() API instead.
*/
static inline __noinline

67
tools/lib/bpf/usdt.c
View File

@ -108,7 +108,7 @@
* code through spec map. This allows BPF applications to quickly fetch the
* actual value at runtime using a simple BPF-side code.
*
* With basics out of the way, let's go over less immeditately obvious aspects
* With basics out of the way, let's go over less immediately obvious aspects
* of supporting USDTs.
*
* First, there is no special USDT BPF program type. It is actually just
@ -189,14 +189,14 @@
#define USDT_NOTE_TYPE 3
#define USDT_NOTE_NAME "stapsdt"
/* should match exactly enum __bpf_usdt_arg_type from bpf_usdt.bpf.h */
/* should match exactly enum __bpf_usdt_arg_type from usdt.bpf.h */
enum usdt_arg_type {
USDT_ARG_CONST,
USDT_ARG_REG,
USDT_ARG_REG_DEREF,
};
/* should match exactly struct __bpf_usdt_arg_spec from bpf_usdt.bpf.h */
/* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */
struct usdt_arg_spec {
__u64 val_off;
enum usdt_arg_type arg_type;
@ -328,9 +328,9 @@ static int sanity_check_usdt_elf(Elf *elf, const char *path)
return -EBADF;
}
#if __BYTE_ORDER == __LITTLE_ENDIAN
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
endianness = ELFDATA2LSB;
#elif __BYTE_ORDER == __BIG_ENDIAN
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
endianness = ELFDATA2MSB;
#else
# error "Unrecognized __BYTE_ORDER__"
@ -843,7 +843,7 @@ static int bpf_link_usdt_detach(struct bpf_link *link)
sizeof(*new_free_ids));
/* If we couldn't resize free_spec_ids, we'll just leak
* a bunch of free IDs; this is very unlikely to happen and if
* system is so exausted on memory, it's the least of user's
* system is so exhausted on memory, it's the least of user's
* concerns, probably.
* So just do our best here to return those IDs to usdt_manager.
*/
@ -1269,6 +1269,61 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec
return len;
}
#elif defined(__s390x__)
/* Do not support __s390__ for now, since user_pt_regs is broken with -m31. */
static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)
{
unsigned int reg;
int arg_sz, len;
long off;
if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", &arg_sz, &off, &reg, &len) == 3) {
/* Memory dereference case, e.g., -2@-28(%r15) */
arg->arg_type = USDT_ARG_REG_DEREF;
arg->val_off = off;
if (reg > 15) {
pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
return -EINVAL;
}
arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
} else if (sscanf(arg_str, " %d @ %%r%u %n", &arg_sz, &reg, &len) == 2) {
/* Register read case, e.g., -8@%r0 */
arg->arg_type = USDT_ARG_REG;
arg->val_off = 0;
if (reg > 15) {
pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
return -EINVAL;
}
arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
} else if (sscanf(arg_str, " %d @ %ld %n", &arg_sz, &off, &len) == 2) {
/* Constant value case, e.g., 4@71 */
arg->arg_type = USDT_ARG_CONST;
arg->val_off = off;
arg->reg_off = 0;
} else {
pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
return -EINVAL;
}
arg->arg_signed = arg_sz < 0;
if (arg_sz < 0)
arg_sz = -arg_sz;
switch (arg_sz) {
case 1: case 2: case 4: case 8:
arg->arg_bitshift = 64 - arg_sz * 8;
break;
default:
pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",
arg_num, arg_str, arg_sz);
return -EINVAL;
}
return len;
}
#else
static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)