From e1b6df598aa86e351437135c76ed38c9a5e3d397 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 7 Apr 2022 23:44:09 +0200 Subject: [PATCH 1/3] libbpf: Minor style improvements in USDT code Fix several typos and references to non-existing headers. Also use __BYTE_ORDER__ instead of __BYTE_ORDER for consistency with the rest of the bpf code - see commit 45f2bebc8079 ("libbpf: Fix endianness detection in BPF_CORE_READ_BITFIELD_PROBED()") for rationale). Signed-off-by: Ilya Leoshkevich Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220407214411.257260-2-iii@linux.ibm.com --- tools/lib/bpf/usdt.bpf.h | 4 ++-- tools/lib/bpf/usdt.c | 12 ++++++------ 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/tools/lib/bpf/usdt.bpf.h b/tools/lib/bpf/usdt.bpf.h index 60237acf6b025..420d743734e12 100644 --- a/tools/lib/bpf/usdt.bpf.h +++ b/tools/lib/bpf/usdt.bpf.h @@ -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. @@ -198,7 +198,7 @@ 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 diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c index b699e720136a9..3dcb79f1e3a74 100644 --- a/tools/lib/bpf/usdt.c +++ b/tools/lib/bpf/usdt.c @@ -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. */ From 6f403d9d530635f533577d37929c61474d6c5d7f Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 7 Apr 2022 23:44:10 +0200 Subject: [PATCH 2/3] libbpf: Make BPF-side of USDT support work on big-endian machines BPF_USDT_ARG_REG_DEREF handling always reads 8 bytes, regardless of the actual argument size. On little-endian the relevant argument bits end up in the lower bits of val, and later on the code that handles all the argument types expects them to be there. On big-endian they end up in the upper bits of val, breaking that expectation. Fix by right-shifting val on big-endian. Signed-off-by: Ilya Leoshkevich Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220407214411.257260-3-iii@linux.ibm.com --- tools/lib/bpf/usdt.bpf.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/lib/bpf/usdt.bpf.h b/tools/lib/bpf/usdt.bpf.h index 420d743734e12..881a2422a8efb 100644 --- a/tools/lib/bpf/usdt.bpf.h +++ b/tools/lib/bpf/usdt.bpf.h @@ -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; From 32e44e4e68ef9ad6272cbf10cfe3745ab2627fc6 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Thu, 7 Apr 2022 23:44:11 +0200 Subject: [PATCH 3/3] libbpf: Add s390-specific USDT arg spec parsing logic The logic is superficially similar to that of x86, but the small differences (no need for register table and dynamic allocation of register names, no $ sign before constants) make maintaining a common implementation too burdensome. Therefore simply add a s390x-specific version of parse_usdt_arg(). Note that while bcc supports index registers, this patch does not. This should not be a problem in most cases, since s390 uses a default value "nor" for STAP_SDT_ARG_CONSTRAINT. Signed-off-by: Ilya Leoshkevich Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220407214411.257260-4-iii@linux.ibm.com --- tools/lib/bpf/usdt.c | 57 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c index 3dcb79f1e3a74..cb9aa455c0dfb 100644 --- a/tools/lib/bpf/usdt.c +++ b/tools/lib/bpf/usdt.c @@ -1269,6 +1269,63 @@ 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 sz, len; + long off; + + if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", &sz, &off, ®, &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", &sz, ®, &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", &sz, &off, &len) == 2) { + /* Constant value case, e.g., 4@71 */ + arg->arg_type = USDT_ARG_CONST; + arg->val_off = off; + arg->reg_off = -1; + } else { + pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, + arg_str); + return -EINVAL; + } + + arg->arg_signed = sz < 0; + if (sz < 0) + sz = -sz; + + switch (sz) { + case 1: case 2: case 4: case 8: + arg->arg_bitshift = 64 - sz * 8; + break; + default: + pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n", + arg_num, arg_str, sz); + return -EINVAL; + } + + return len; +} + #else static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg)