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riscv/stacktrace: Fix stack output without ra on the stack top
When a function doesn't have a callee, then it will not push ra into the stack, such as lkdtm_BUG() function, addi sp,sp,-16 sd s0,8(sp) addi s0,sp,16 ebreak The struct stackframe use {fp,ra} to get information from stack, if walk_stackframe() with pr_regs, we will obtain wrong value and bad stacktrace, [<ffffffe00066c56c>] lkdtm_BUG+0x6/0x8 ---[ end trace 18da3fbdf08e25d5 ]--- Correct the next fp and pc, after that, full stacktrace shown as expects, [<ffffffe00066c56c>] lkdtm_BUG+0x6/0x8 [<ffffffe0008b24a4>] lkdtm_do_action+0x14/0x1c [<ffffffe00066c372>] direct_entry+0xc0/0x10a [<ffffffe000439f86>] full_proxy_write+0x42/0x6a [<ffffffe000309626>] vfs_write+0x7e/0x214 [<ffffffe00030992a>] ksys_write+0x98/0xc0 [<ffffffe000309960>] sys_write+0xe/0x16 [<ffffffe0002014bc>] ret_from_syscall+0x0/0x2 ---[ end trace 61917f3d9a9fadcd ]--- Signed-off-by: Chen Huang <chenhuang5@huawei.com> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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@ -54,9 +54,15 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
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/* Unwind stack frame */
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frame = (struct stackframe *)fp - 1;
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sp = fp;
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fp = frame->fp;
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pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
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(unsigned long *)(fp - 8));
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if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
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fp = frame->ra;
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pc = regs->ra;
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} else {
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fp = frame->fp;
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pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
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(unsigned long *)(fp - 8));
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}
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}
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}
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