git: f9246e148488 - main - linux: Implement some bits of PTRACE_PEEKUSER

[Edward Tomasz Napierala]

The branch main has been updated by trasz:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=f9246e14848820664539763b72b6fdef408d20e4

commit f9246e14848820664539763b72b6fdef408d20e4
Author:     Edward Tomasz Napierala <tr...@freebsd.org>
AuthorDate: 2021-10-17 11:20:16 +0000
Commit:     Edward Tomasz Napierala <tr...@freebsd.org>
CommitDate: 2021-10-17 11:20:21 +0000

    linux: Implement some bits of PTRACE_PEEKUSER
    
    This makes Linux gdb from Bionic a little less broken.
    
    Sponsored By:   EPSRC
    Differential Revision:  https://reviews.freebsd.org/D32455
---
 sys/amd64/linux/linux_ptrace.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/sys/amd64/linux/linux_ptrace.c b/sys/amd64/linux/linux_ptrace.c
index a59702757972..39587ec9b2ad 100644
--- a/sys/amd64/linux/linux_ptrace.c
+++ b/sys/amd64/linux/linux_ptrace.c
@@ -97,6 +97,11 @@ __FBSDID("$FreeBSD$");
 #define        LINUX_PTRACE_SYSCALL_INFO_ENTRY 1
 #define        LINUX_PTRACE_SYSCALL_INFO_EXIT  2
 
+#define LINUX_PTRACE_PEEKUSER_ORIG_RAX 120
+#define LINUX_PTRACE_PEEKUSER_RIP      128
+#define LINUX_PTRACE_PEEKUSER_CS       136
+#define LINUX_PTRACE_PEEKUSER_DS       184
+
 #define        LINUX_ARCH_AMD64                0xc000003e
 
 static int
@@ -286,9 +291,37 @@ linux_ptrace_peek(struct thread *td, pid_t pid, void 
*addr, void *data)
 static int
 linux_ptrace_peekuser(struct thread *td, pid_t pid, void *addr, void *data)
 {
+       struct reg b_reg;
+       uint64_t val;
+       int error;
 
-       linux_msg(td, "PTRACE_PEEKUSER not implemented; returning EINVAL");
-       return (EINVAL);
+       error = kern_ptrace(td, PT_GETREGS, pid, &b_reg, 0);
+       if (error != 0)
+               return (error);
+
+       switch ((uintptr_t)addr) {
+       case LINUX_PTRACE_PEEKUSER_ORIG_RAX:
+               val = b_reg.r_rax;
+               break;
+       case LINUX_PTRACE_PEEKUSER_RIP:
+               val = b_reg.r_rip;
+               break;
+       case LINUX_PTRACE_PEEKUSER_CS:
+               val = b_reg.r_cs;
+               break;
+       case LINUX_PTRACE_PEEKUSER_DS:
+               val = b_reg.r_ds;
+               break;
+       default:
+               linux_msg(td, "PTRACE_PEEKUSER offset %ld not implemented; "
+                   "returning EINVAL", (uintptr_t)addr);
+               return (EINVAL);
+       }
+
+       error = copyout(&val, data, sizeof(val));
+       td->td_retval[0] = error;
+
+       return (error);
 }
 
 static int