From: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com
commit ec6d0dde71d760aa60316f8d1c9a1b0d99213529 upstream.
On execve[at], we are zero'ing out most of the thread register state including gpr[0], which contains the syscall number. Due to this, we fail to trigger the syscall exit tracepoint properly. Fix this by retaining gpr[0] in the thread register state.
Before this patch: # tail /sys/kernel/debug/tracing/trace cat-123 [000] ..... 61.449351: sys_execve(filename: 7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8) cat-124 [000] ..... 62.428481: sys_execve(filename: 7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8) echo-125 [000] ..... 65.813702: sys_execve(filename: 7fffa6b23378, argv: 7fffa6b233a0, envp: 7fffa6b233b0) echo-125 [000] ..... 65.822214: sys_execveat(fd: 0, filename: 1009ac48, argv: 7ffff65d0c98, envp: 7ffff65d0ca8, flags: 0)
After this patch: # tail /sys/kernel/debug/tracing/trace cat-127 [000] ..... 100.416262: sys_execve(filename: 7fffa41b3448, argv: 7fffa41b33e0, envp: 7fffa41b33f8) cat-127 [000] ..... 100.418203: sys_execve -> 0x0 echo-128 [000] ..... 103.873968: sys_execve(filename: 7fffa41b3378, argv: 7fffa41b33a0, envp: 7fffa41b33b0) echo-128 [000] ..... 103.875102: sys_execve -> 0x0 echo-128 [000] ..... 103.882097: sys_execveat(fd: 0, filename: 1009ac48, argv: 7fffd10d2148, envp: 7fffd10d2158, flags: 0) echo-128 [000] ..... 103.883225: sys_execveat -> 0x0
Cc: stable@vger.kernel.org Signed-off-by: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Tested-by: Sumit Dubey2 Sumit.Dubey2@ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20220609103328.41306-1-naveen.n.rao@linux.vnet.ibm... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1800,7 +1800,7 @@ void start_thread(struct pt_regs *regs, tm_reclaim_current(0); #endif
- memset(regs->gpr, 0, sizeof(regs->gpr)); + memset(®s->gpr[1], 0, sizeof(regs->gpr) - sizeof(regs->gpr[0])); regs->ctr = 0; regs->link = 0; regs->xer = 0;