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author | Puranjay Mohan <puranjay12@gmail.com> | 2023-03-07 15:04:40 +0300 |
---|---|---|
committer | Andrii Nakryiko <andrii@kernel.org> | 2023-03-08 02:35:53 +0300 |
commit | 720d93b60aec22abcb2a5b6d8de472f3a50694b1 (patch) | |
tree | 0d9224322daf284d462b8043b8ac069a97c83aed /tools | |
parent | 98e678e9bc5859dec605794730ad37d26789bd30 (diff) | |
download | linux-720d93b60aec22abcb2a5b6d8de472f3a50694b1.tar.xz |
libbpf: USDT arm arg parsing support
Parsing of USDT arguments is architecture-specific; on arm it is
relatively easy since registers used are r[0-10], fp, ip, sp, lr,
pc. Format is slightly different compared to aarch64; forms are
- "size @ [ reg, #offset ]" for dereferences, for example
"-8 @ [ sp, #76 ]" ; " -4 @ [ sp ]"
- "size @ reg" for register values; for example
"-4@r0"
- "size @ #value" for raw values; for example
"-8@#1"
Add support for parsing USDT arguments for ARM architecture.
To test the above changes QEMU's virt[1] board with cortex-a15
CPU was used. libbpf-bootstrap's usdt example[2] was modified to attach
to a test program with DTRACE_PROBE1/2/3/4... probes to test different
combinations.
[1] https://www.qemu.org/docs/master/system/arm/virt.html
[2] https://github.com/libbpf/libbpf-bootstrap/blob/master/examples/c/usdt.bpf.c
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230307120440.25941-3-puranjay12@gmail.com
Diffstat (limited to 'tools')
-rw-r--r-- | tools/lib/bpf/usdt.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c index 72faa8162e34..b8402e3f9eb2 100644 --- a/tools/lib/bpf/usdt.c +++ b/tools/lib/bpf/usdt.c @@ -1465,6 +1465,86 @@ static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec return len; } +#elif defined(__arm__) + +static int calc_pt_regs_off(const char *reg_name) +{ + static struct { + const char *name; + size_t pt_regs_off; + } reg_map[] = { + { "r0", offsetof(struct pt_regs, uregs[0]) }, + { "r1", offsetof(struct pt_regs, uregs[1]) }, + { "r2", offsetof(struct pt_regs, uregs[2]) }, + { "r3", offsetof(struct pt_regs, uregs[3]) }, + { "r4", offsetof(struct pt_regs, uregs[4]) }, + { "r5", offsetof(struct pt_regs, uregs[5]) }, + { "r6", offsetof(struct pt_regs, uregs[6]) }, + { "r7", offsetof(struct pt_regs, uregs[7]) }, + { "r8", offsetof(struct pt_regs, uregs[8]) }, + { "r9", offsetof(struct pt_regs, uregs[9]) }, + { "r10", offsetof(struct pt_regs, uregs[10]) }, + { "fp", offsetof(struct pt_regs, uregs[11]) }, + { "ip", offsetof(struct pt_regs, uregs[12]) }, + { "sp", offsetof(struct pt_regs, uregs[13]) }, + { "lr", offsetof(struct pt_regs, uregs[14]) }, + { "pc", offsetof(struct pt_regs, uregs[15]) }, + }; + int i; + + for (i = 0; i < ARRAY_SIZE(reg_map); i++) { + if (strcmp(reg_name, reg_map[i].name) == 0) + return reg_map[i].pt_regs_off; + } + + pr_warn("usdt: unrecognized register '%s'\n", reg_name); + return -ENOENT; +} + +static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz) +{ + char reg_name[16]; + int len, reg_off; + long off; + + if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] , #%ld ] %n", + arg_sz, reg_name, &off, &len) == 3) { + /* Memory dereference case, e.g., -4@[fp, #96] */ + arg->arg_type = USDT_ARG_REG_DEREF; + arg->val_off = off; + reg_off = calc_pt_regs_off(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off = reg_off; + } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) { + /* Memory dereference case, e.g., -4@[sp] */ + arg->arg_type = USDT_ARG_REG_DEREF; + arg->val_off = 0; + reg_off = calc_pt_regs_off(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off = reg_off; + } else if (sscanf(arg_str, " %d @ #%ld %n", arg_sz, &off, &len) == 2) { + /* Constant value case, e.g., 4@#5 */ + arg->arg_type = USDT_ARG_CONST; + arg->val_off = off; + arg->reg_off = 0; + } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) { + /* Register read case, e.g., -8@r4 */ + arg->arg_type = USDT_ARG_REG; + arg->val_off = 0; + reg_off = calc_pt_regs_off(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off = reg_off; + } else { + pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str); + return -EINVAL; + } + + return len; +} + #else static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz) |