[PATCH v2] libbpf: Fix the incorrect register read for syscalls on x86_64

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Currently, rcx is read as the fourth parameter of syscall on x86_64.
But x86_64 Linux System Call convention uses r10 actually.
This commit adds the wrapper for users who want to access to
syscall params to analyze the user space.

Changelog:
----------
v1 -> v2:
- Rebase to current bpf-next
https://lore.kernel.org/bpf/20211222213924.1869758-1-andrii@xxxxxxxxxx/

Signed-off-by: Kenta Tada <Kenta.Tada@xxxxxxxx>
---
 tools/lib/bpf/bpf_tracing.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 90f56b0f585f..4c3df8c122a4 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -70,6 +70,7 @@
 #define __PT_PARM2_REG si
 #define __PT_PARM3_REG dx
 #define __PT_PARM4_REG cx
+#define __PT_PARM4_REG_SYSCALL r10 /* syscall uses r10 */
 #define __PT_PARM5_REG r8
 #define __PT_RET_REG sp
 #define __PT_FP_REG bp
@@ -99,6 +100,7 @@
 #define __PT_PARM2_REG rsi
 #define __PT_PARM3_REG rdx
 #define __PT_PARM4_REG rcx
+#define __PT_PARM4_REG_SYSCALL r10 /* syscall uses r10 */
 #define __PT_PARM5_REG r8
 #define __PT_RET_REG rsp
 #define __PT_FP_REG rbp
@@ -226,6 +228,7 @@ struct pt_regs;
 #define PT_REGS_PARM2(x) (__PT_REGS_CAST(x)->__PT_PARM2_REG)
 #define PT_REGS_PARM3(x) (__PT_REGS_CAST(x)->__PT_PARM3_REG)
 #define PT_REGS_PARM4(x) (__PT_REGS_CAST(x)->__PT_PARM4_REG)
+#define PT_REGS_PARM4_SYSCALL(x) (__PT_REGS_CAST(x)->__PT_PARM4_REG_SYSCALL)
 #define PT_REGS_PARM5(x) (__PT_REGS_CAST(x)->__PT_PARM5_REG)
 #define PT_REGS_RET(x) (__PT_REGS_CAST(x)->__PT_RET_REG)
 #define PT_REGS_FP(x) (__PT_REGS_CAST(x)->__PT_FP_REG)
@@ -237,6 +240,7 @@ struct pt_regs;
 #define PT_REGS_PARM2_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM2_REG)
 #define PT_REGS_PARM3_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM3_REG)
 #define PT_REGS_PARM4_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM4_REG)
+#define PT_REGS_PARM4_CORE_SYSCALL(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM4_REG_SYSCALL)
 #define PT_REGS_PARM5_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM5_REG)
 #define PT_REGS_RET_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_RET_REG)
 #define PT_REGS_FP_CORE(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_FP_REG)
@@ -292,6 +296,22 @@ struct pt_regs;
 
 #endif /* defined(bpf_target_defined) */
 
+#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1(x)
+#define PT_REGS_PARM2_SYSCALL(x) PT_REGS_PARM2(x)
+#define PT_REGS_PARM3_SYSCALL(x) PT_REGS_PARM3(x)
+#ifndef PT_REGS_PARM4_SYSCALL
+#define PT_REGS_PARM4_SYSCALL(x) PT_REGS_PARM4(x)
+#endif
+#define PT_REGS_PARM5_SYSCALL(x) PT_REGS_PARM5(x)
+
+#define PT_REGS_PARM1_CORE_SYSCALL(x) PT_REGS_PARM1_CORE(x)
+#define PT_REGS_PARM2_CORE_SYSCALL(x) PT_REGS_PARM2_CORE(x)
+#define PT_REGS_PARM3_CORE_SYSCALL(x) PT_REGS_PARM3_CORE(x)
+#ifndef PT_REGS_PARM4_CORE_SYSCALL
+#define PT_REGS_PARM4_CORE_SYSCALL(x) PT_REGS_PARM4_CORE(x)
+#endif
+#define PT_REGS_PARM5_CORE_SYSCALL(x) PT_REGS_PARM5_CORE(x)
+
 #ifndef ___bpf_concat
 #define ___bpf_concat(a, b) a ## b
 #endif
-- 
2.32.0




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