Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-09 Thread Madhavan T. Venkataraman
>> Also, the Function Graph Tracer modifies the return address of a traced >> function to a return trampoline to gather tracing data on function return. >> Stack traces taken from that trampoline and functions it calls are >> unreliable as the original return address may not be available in >> th

Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-09 Thread Madhavan T. Venkataraman
On 4/9/21 6:31 AM, Mark Brown wrote: > On Thu, Apr 08, 2021 at 02:23:39PM -0500, Madhavan T. Venkataraman wrote: >> On 4/8/21 11:58 AM, Mark Brown wrote: > >>> This looks good to me however I'd really like someone who has a firmer >>> understanding of what ftrace is doing to double check as it

Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-09 Thread Mark Rutland
On Mon, Apr 05, 2021 at 03:43:12PM -0500, madve...@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" > > When CONFIG_DYNAMIC_FTRACE_WITH_REGS is enabled and tracing is activated > for a function, the ftrace infrastructure is called for the function at > the very beginning. Ftrace crea

Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-09 Thread Mark Brown
On Thu, Apr 08, 2021 at 02:23:39PM -0500, Madhavan T. Venkataraman wrote: > On 4/8/21 11:58 AM, Mark Brown wrote: > > This looks good to me however I'd really like someone who has a firmer > > understanding of what ftrace is doing to double check as it is entirely > > likely that I am missing case

Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-08 Thread Madhavan T. Venkataraman
On 4/8/21 11:58 AM, Mark Brown wrote: > On Mon, Apr 05, 2021 at 03:43:12PM -0500, madve...@linux.microsoft.com wrote: >> From: "Madhavan T. Venkataraman" >> >> When CONFIG_DYNAMIC_FTRACE_WITH_REGS is enabled and tracing is activated >> for a function, the ftrace infrastructure is called for the

Re: [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-08 Thread Mark Brown
On Mon, Apr 05, 2021 at 03:43:12PM -0500, madve...@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" > > When CONFIG_DYNAMIC_FTRACE_WITH_REGS is enabled and tracing is activated > for a function, the ftrace infrastructure is called for the function at > the very beginning. Ftrace crea

[RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable

2021-04-05 Thread madvenka
From: "Madhavan T. Venkataraman" When CONFIG_DYNAMIC_FTRACE_WITH_REGS is enabled and tracing is activated for a function, the ftrace infrastructure is called for the function at the very beginning. Ftrace creates two frames: - One for the traced function - One for the caller of