powerpc/fsl_booke: Allocate separate TLBCAMs for readonly memory

Reorganise TLBCAM allocation so that when STRICT_KERNEL_RWX is
enabled, TLBCAMs are allocated such that readonly memory uses
different TLBCAMs.

This results in an allocation looking like:

Memory CAM mapping: 4/4/4/1/1/1/1/16/16/16/64/64/64/256/256 Mb, residual: 256Mb
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8ca169bc288261a0e0558712f979023c3a960ebb.1634292136.git.christophe.leroy@csgroup.eu

arch/powerpc/mm/nohash/fsl_book3e.c

@@ -171,15 +171,34 @@ static unsigned long map_mem_in_cams_addr(phys_addr_t phys, unsigned long virt,
 {
 	int i;
 	unsigned long amount_mapped = 0;
+	unsigned long boundary;
+
+	if (strict_kernel_rwx_enabled())
+		boundary = (unsigned long)(_sinittext - _stext);
+	else
+		boundary = ram;
 
 	/* Calculate CAM values */
-	for (i = 0; ram && i < max_cam_idx; i++) {
+	for (i = 0; boundary && i < max_cam_idx; i++) {
+		unsigned long cam_sz;
+		pgprot_t prot = PAGE_KERNEL_X;
+
+		cam_sz = calc_cam_sz(boundary, virt, phys);
+		if (!dryrun)
+			settlbcam(i, virt, phys, cam_sz, pgprot_val(prot), 0);
+
+		boundary -= cam_sz;
+		amount_mapped += cam_sz;
+		virt += cam_sz;
+		phys += cam_sz;
+	}
+	for (ram -= amount_mapped; ram && i < max_cam_idx; i++) {
 		unsigned long cam_sz;
+		pgprot_t prot = PAGE_KERNEL_X;
 
 		cam_sz = calc_cam_sz(ram, virt, phys);
 		if (!dryrun)
-			settlbcam(i, virt, phys, cam_sz,
-				  pgprot_val(PAGE_KERNEL_X), 0);
+			settlbcam(i, virt, phys, cam_sz, pgprot_val(prot), 0);
 
 		ram -= cam_sz;
 		amount_mapped += cam_sz;