Hi Will,
On 6 January 2014 19:30, Will Deacon will.deacon@arm.com wrote:
Hi Jean,
Thanks for the updated patches. One minor comment on this one.
On Mon, Dec 30, 2013 at 04:25:30PM +0000, Jean Pihet wrote:
From: Jean Pihet jean.pihet@newoldbits.com
This patch implements the functions required for the perf registers API, allowing the perf tool to interface kernel register dumps with libunwind in order to provide userspace backtracing. Compat mode is also supported.
[...]
+u64 perf_reg_value(struct pt_regs *regs, int idx) +{
if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_MAX))return 0;While this is probably fine, I'd feel more comfortable if you had separate limit checks for native and compat...
In fact in the native and compat modes the same set of registers are accessed, based on the native regs that are registered to the perf event core, cf. the definition of PERF_REGS_MASK in tools/perf/arch/arm64/include/perf_regs.h.
The regs set could be registered differently based on the binary to trace, but unfortunately the perf core code does not allow that.
I would leave the code as is, what do you think?
Cheers, Jean
/** Compat (i.e. 32 bit) mode:* - PC has been set in the pt_regs struct in kernel_entry,* - Handle SP and LR here.*/if (compat_user_mode(regs)) {i.e. have a WARN_ON_ONCE here for the compat structure size.
if ((u32)idx == PERF_REG_ARM64_SP)return regs->compat_sp;if ((u32)idx == PERF_REG_ARM64_LR)return regs->compat_lr;}then stick an else here with the original check.
Make sense?
Will