Re: [PATCH v6 4/4] risc/purgatory: Add linker script

On Mon, 1 May 2023 at 19:41, Conor Dooley [off-list ref] wrote:

quoted

On Mon, May 01, 2023 at 02:38:22PM +0200, Ricardo Ribalda wrote:

quoted

If PGO is enabled, the purgatory ends up with multiple .text sections.
This is not supported by kexec and crashes the system.

Cc: stable@vger.kernel.org
Fixes: 930457057abe ("kernel/kexec_file.c: split up __kexec_load_puragory")
Signed-off-by: Ricardo Ribalda <redacted>
---
 arch/riscv/purgatory/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index 5730797a6b40..cf3a44121a90 100644
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile

@@ -35,6 +35,11 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
 CFLAGS_string.o := -D__DISABLE_EXPORTS
 CFLAGS_ctype.o := -D__DISABLE_EXPORTS

+# When profile optimization is enabled, llvm emits two different overlapping
+# text sections, which is not supported by kexec. Remove profile optimization
+# flags.
+KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(KBUILD_CFLAGS))

With the caveat of not being au fait with the workings of either PGO or
of purgatory, how come you modify KBUILD_CFLAGS here rather than the
purgatory specific PURGATORY_CFLAGS that are used later in the file?

Definitely, not a Makefile expert here, but when I tried this:

@@ -35,6 +40,7 @@ PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
 PURGATORY_CFLAGS := -mcmodel=large -ffreestanding
-fno-zero-initialized-in-bss -g0
 PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
 PURGATORY_CFLAGS += -fno-stack-protector
+PURGATORY_CFLAGS := $(filter-out -fprofile-sample-use=%
-fprofile-use=%,$(KBUILD_CFLAGS))

It did not work.