summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorDeepak Gupta <debug@rivosinc.com>2023-10-27 01:38:23 +0200
committerAndrew Morton <akpm@linux-foundation.org>2023-11-01 20:46:59 +0100
commitcd24f44050f31d69ed5851b55ef77ea6346aa814 (patch)
tree508397661af55316c485c47c4d23c69e3a48bdc6
parentocfs2: fix a spelling typo in comment (diff)
downloadlinux-cd24f44050f31d69ed5851b55ef77ea6346aa814.tar.xz
linux-cd24f44050f31d69ed5851b55ef77ea6346aa814.zip
scripts/gdb: add lx_current support for riscv
csr_sscratch CSR holds current task_struct address when hart is in user space. Trap handler on entry spills csr_sscratch into "tp" (x2) register and zeroes out csr_sscratch CSR. Trap handler on exit reloads "tp" with expected user mode value and place current task_struct address again in csr_sscratch CSR. This patch assumes "tp" is pointing to task_struct. If value in csr_sscratch is numerically greater than "tp" then it assumes csr_sscratch is correct address of current task_struct. This logic holds when - hart is in user space, "tp" will be less than csr_sscratch. - hart is in kernel space but not in trap handler, "tp" will be more than csr_sscratch (csr_sscratch being equal to 0). - hart is executing trap handler - "tp" is still pointing to user mode but csr_sscratch contains ptr to task_struct. Thus numerically higher. - "tp" is pointing to task_struct but csr_sscratch now contains either 0 or numerically smaller value (transiently holds user mode tp) Link: https://lkml.kernel.org/r/20231026233837.612405-1-debug@rivosinc.com Signed-off-by: Deepak Gupta <debug@rivosinc.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com> Acked-by: Palmer Dabbelt <palmer@rivosinc.com> Tested-by: Hsieh-Tseng Shen <woodrow.shen@sifive.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Glenn Washburn <development@efficientek.com> Cc: Jan Kiszka <jan.kiszka@siemens.com> Cc: Jeff Xie <xiehuan09@gmail.com> Cc: Kieran Bingham <kbingham@kernel.org> Cc: Palmer Dabbelt <palmer@rivosinc.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--scripts/gdb/linux/cpus.py15
1 files changed, 15 insertions, 0 deletions
diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index 255dc18cb9da..cba589e5b57d 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -179,6 +179,21 @@ def get_current_task(cpu):
else:
raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
"while running in userspace(EL0)")
+ elif utils.is_target_arch("riscv"):
+ current_tp = gdb.parse_and_eval("$tp")
+ scratch_reg = gdb.parse_and_eval("$sscratch")
+
+ # by default tp points to current task
+ current_task = current_tp.cast(task_ptr_type)
+
+ # scratch register is set 0 in trap handler after entering kernel.
+ # When hart is in user mode, scratch register is pointing to task_struct.
+ # and tp is used by user mode. So when scratch register holds larger value
+ # (negative address as ulong is larger value) than tp, then use scratch register.
+ if (scratch_reg.cast(utils.get_ulong_type()) > current_tp.cast(utils.get_ulong_type())):
+ current_task = scratch_reg.cast(task_ptr_type)
+
+ return current_task.dereference()
else:
raise gdb.GdbError("Sorry, obtaining the current task is not yet "
"supported with this arch")